Dissertations / Theses on the topic 'Milk production of dairy cow'

1) A review of the literature relating to the amino acid requirements in ruminants is presented. It was concluded from this review that the amino acids most likely to be limiting for milk production were lysine and methionine. 2) The object of this project was, by using the approach developed by Storm (1982), to identify which amino acids in a test protein were limiting for production in the lactating dairy cow. The nutritional requirements of the animals were met by the total intragastric infusion technique; this system eliminated the problems of rumen fermentation, and allowed precise control of the amino acid supply to the small intestine of the experimental animals. 3) The identification of the limiting amino acids involved several steps which included:a) the estimation of the efficiency of nitrogen and amino acid nitrogen utilisation by the cow,b) calculation of the supplement required to increase the efficiency of N utilisation to a maximum of 1.0,c) the demonstration that a similar response in production could be obtained from a supplement of casein, or a mixture of synthetic essential and non-essential amino acids in similar proportions to those in casein,d) to establish that the removal of non-essential amino acids had no effect on production responses ande) measurement of the changes in production obtained by removal of individual essential amino acids from the amino acid supplement, according to the theoretical basis assumed by Storm (1982). 4) The efficiency of nitrogen utilisation of the test protein, casein was estalished under nitrogen limiting conditions from the regression of productive nitrogen (milk nitrogen and retained nitrogen) on nitrogen input for cows in early, mid and late lactation and cows in the dry period. The values obtained for the four stages were 0.693, 0.683, 0.583 and 0.607 for early, mid and late lactation and the dry period respectively. Analysis of the data revealed that the slopes of these relationships did not differ significantly. It appears, therefore, that under nitrogen limiting conditions, the efficiency of nitrogen utilisation was not effected by stage of lactation. The overall value obtained for the efficiency of utilisation of casein nitrogen supplied at the abomasum was 0.66. 5) Assuming that the proportion of amino acid nitrogen in total nitrogen was 0.88 and the true digestibility of amino acid nitrogen was 0.95, the efficiency of amino acid nitrogen utilisation (UAAN) could be calculated as follows:U_AAN = rm Efficiency of Nitrogen utilisationover rm (Proportion of AAN in total nitrogen) (True digestibility)Therefore, the supplement of amino acids required to raise the efficiency of amino acid nitrogen utilisation to the optimum of 1.0 was rm 1-UAANover rm UAAN of the basal casein input of amino acid nitrogen. 6) Using the value of 0.693 for the efficiency of utilisation of casein nitrogen, the amino acid supplement required was 0.206 of the basal casein input of amino acid nitrogen. Using this supplement it was established that a similar response in productive nitrogen could be obtained by supplementing the basal input of casein with either casein or a mixture of essential and non-essential amino acids in similar proportions to that of casein or a mixture of essential amino acids alone. The non-essential amino acids were excluded from the supplement in further experiments. 7) The efficiency of nitrogen utilisation used in the final experiment was that of mid lactation cows 0.683, as the cows were approaching mid lactation. Essential amino acids were removed from the supplement either singly or in pairs and changes in productive nitrogen were measured. Significant decreases in productive nitrogen were obtained by the removal of lysine, methionine and histidine. Removal of phenylalanine resulted in decreases in productive nitrogen, although this did not reach significance (p < 0.10). The average percent decrease in productive nitrogen with.

With global emissions estimated at 7.1 Gt CO2 eq per annum, livestock represents 14.5% of all human-induced emissions and it is considered to be the largest source of greenhouse gas (GHG) emissions from the agricultural sector. However, livestock can contribute to convert nutrients from plant biomass into animal-sourced foods, which are rich in essential macro and micronutrients in the form of milk and meat, thereby utilizing resources that cannot otherwise be consumed by humans. Livestock also contributes to global food security and poverty reduction, providing regular income to producers. To achieve a sustainable supply of animal origin food, farmers need, therefore, to identify strategies, in terms of livestock management and feeding, forage systems and feed growing practices, that make the best use of available resources and minimize the potential environmental impact. The studies of the PhD thesis were mainly developed inside the Life project “Forage4Climate”, a four years project, aimed at demonstrating that forage systems connected to milk production can promote climate change mitigation. The aim of the PhD thesis was the evaluation of GHG emission, related to dairy cattle milk production. Specific aims were: • to identify and evaluate the most common forage systems adopted in dairy cow farms in the Po plain, selecting the systems that can improve milk production and soil carbon (C) sequestration reducing emissions per kg of milk; • to evaluate commercial diets related to these different forage systems, in order to directly assess their digestibility, milk and methane (CH4) production; • to identify, through a survey analysis, the main ingredients used in the total mixed ration (TMR) of high producing lactating cows, in order to assess the best diet composition that can lead to high feed efficiency (FE) and low global warming potential (GWP) at commercial farms scale; • in a future perspective of circular economy, to study the exploitation of different inedible human by-products as growing substrates for Hermetia Illucens larvae, in order to substitute soybean meal (SBM) in the livestock diets with insect proteins. A total of 46 dairy cattle farms in Lombardy, Piedmont and Emilia-Romagna were visited, in order to map the main forage systems adopted in each area and to characterize them for GHG emission related to milk production (FPCM, fat and protein corrected milk), and soil organic C stock. The evaluation of environmental impact, in terms of GWP, related to the different forage systems was carried out though a Life Cycle Assessment (LCA) method, using the Software SIMAPRO. Six forage systems based on different forages were identified. The main results in terms of GHG per unit milk were: - CONV - Conventional corn silage system: 1.37 kg CO2 eq/kg FPCM (SD 0.26) - HQFS - High quality forage system: 1.18 kg CO2 eq/kg FPCM (SD 0.13) - WICE - Winter cereal silage system: 1.44 kg CO2 eq/kg FPCM (SD 0.43) - MIXED - Mixed less intensive system: 1.36 kg CO2 eq/kg FPCM (SD 0.26) - PR FRESH- Hay and fresh forage system for Parmigiano Reggiano PDO cheese production: 1.51 kg CO2 eq/kg FPCM (SD 0.23) - PR DRY- Hay system for Parmigiano Reggiano PDO cheese production: 1.36 kg CO2 eq/kg FPCM (SD 0.19). The HQFS system registered the lowest value for GWP, mainly due to the higher milk production per cow (daily FPCM/head). More intensive systems, such as HQFS, confirmed that milk production per cow is negatively related to the impact per kilogram of product, as highlighted also by a PROC GLM analysis. The HQFS system also resulted to be more sustainable, in terms of feed self-sufficiency, as it provided a high amount of dry matter (DM) per hectare, consisting of high digestible forages. Despite the lowest value for GWP, the forage system identified as HQFS showed the lowest organic C soil density: 5.6 kg/m2 (SD 1.1). On the contrary, PR FRESH showed the highest value in terms of organic C density in the soil: 9.7 kg/m2 (SD 2.2), compared with an average of 6.7 kg/m2 (SD 0.88) for the other systems. Further investigations are needed to consider environmental sustainability over a wider spectrum. Enteric CH4 was the main contributor to GWP for all forage systems: on average 45.6% (SD 3.89). For this reason, an in vivo evaluation of CH4 and milk production of lactating dairy cows fed four different diets, obtained from the forage systems identified, was performed. Also digestibility of the diets, energy and nitrogen (N) balance were assessed. Four pairs of Italian Friesian lactating cows were used in a repeated Latin Square design, using individual open circuit respiration chambers to determine dry matter intake (DMI), milk production and CH4 emission and to allow total faeces and urine collection for the determination of N and energy balances. Four diets, based on the following main forages, were tested: corn silage (49.3% DM; CS), alfalfa silage (26.8% DM; AS), wheat silage (20.0% DM; WS), hay-based diet (25.3% DM of both alfalfa and Italian ryegrass hays; PR) typical of the area of Parmigiano Reggiano cheese production. Feeding cows with PR diet significantly increased DMI (23.4 kg/d; P=0.006), compared with the others (on average, 20.7 kg/d), while this diet resulted to be the least digestible (e.g. DM digestibility=64.9 vs 71.7% of the other diets, on average). This is probably the reason why, despite higher DMI of cows fed PR diet, the animals did not show higher production, both in terms of milk (kg/d) and energy corrected milk (ECM; kg/d), compared with the other treatments. The urea N concentration was higher in milk of cows fed WS diet (13.8) and lower for cows fed AS diet (9.24). This was also correlated to the highest urinary N excretion (g/d) for cows fed WS diet (189.5 vs 147.0 on average for the other diets). The protein digestibility was higher for cows fed CS and WS diets (on average 68.5%) than for cows fed AS and PR (on average 57.0%); the dietary soybean inclusion was higher for CS and WS than AS and PR. The higher values for aNDFom digestibility were obtained for CS (50.7%) and AS (47.4%) diets. The rumen fermentation pattern was affected by diet; in particular PR diet, characterized by a lower content of NFC and a higher content of aNDFom as compared to CS diet, determined a higher rumen pH and decreased propionate production as compared to CS. Feeding cows with PR diet increased the acetate:propionate ratio in comparison with CS (3.30 vs 2.44 for PR and CS, respectively). Ruminal environment characteristics (i.e higher pH and higher acetate: propionate ratio), together with increased DMI, led cows fed PR DRY diet to have greater (P=0.046) daily production of CH4 (413.4 g/d), compared to those fed CONV diet (378.2 g/d). However, no differences were observed when CH4 was expressed as g/kg DMI or g/kg milk. Hay based diet (PR) was characterized by the lowest digestible and metabolizable energy contents which overall determined a lower NEL content for PR than CS diet (1.36 vs 1.70 Mcal/kg DM respectively for PR and CS diets). In order to meet the high demand of nutrients needed to assure high milk production, in addition to fodder a lot of concentrates are also used in dairy cows’ TMR. A survey analysis conducted in commercial farms was performed to evaluate the GWP of different lactating cow TMR and to identify the best dietary strategies to increase the FE and to reduce the enteric CH4 emission. A total of 171 dairy herds were selected: data about DMI, lactating cows TMR composition, milk production and composition were provided by farmers. Diet GWP (kg CO2 eq) was calculated as sum of GWP of each ingredient considering inputs needed at field level, feed processing and transport. For SBM, land use change was included in the assessment. Enteric CH4 production (g/d) was estimated using the equation of Hristov et al. (2013) in order to calculate CH4 emission for kg of FPCM. The dataset was analysed by GLM and logistic analysis using SAS 9.4. The results of frequency distribution showed that there was a wide variation among farms for the GWP of TMR: approximately 25% of the surveyed farms showed a diet GWP of 15 kg CO2 eq, 20% of 13 kg CO2 eq and 16.7% of 17 kg CO2 eq. The variation among farms is due to the feed used. Among feed, SBM had the highest correlation with the GWP of the TMR with the following equation: TMR GWP (kg CO2 eq) = 2.49*kg SBM + 6.9 (r2=0.547). Moreover, an inclusion of SBM >15% of diet DM did not result in higher milk production with respect to a lower inclusion (≤15%). Average daily milk production of cows was 29.8 (SD 4.83) kg with a fat and protein content (%) of 3.86 (SD 0.22) and 3.40 (SD 0.14), respectively. The average value of DMI (kg/d) of lactating cows was 22.3 (SD 2.23). The logistic analysis demonstrated that a level of corn silage ≤ 30% on diet DM was associated with higher FE. Almost 50% percent of the farms had an average value of 15.0 g CH4/kg FPCM and about 30% a value of 12.5 g CH4/kg FPCM. The results demonstrated that a lower enteric CH4 production was related to inclusion (% on diet DM) of less than 12% of alfalfa hay and more than 30% of corn silage. Diets with more than 34% of NDF determined higher CH4 production (≥14.0 g/kg FPCM) compared with diets with lower NDF content. On the contrary, a lower enteric CH4 production (<14.0 g/kg FPCM) was related to diets characterized by more than 1.61 NEl (Mcal/kg) and more than 4% of ether extract. The variability in the GWP of TMR shows a significant potential to reduce both the GWP of the diet through a correct choice and inclusion level in the ration of the ingredients (mainly SBM) and the possibility to decrease CH4 enteric emission associated to milk production. Looking forward, in order to evaluate the opportunity of alternative protein sources in the cow diet, to reduce SBM, waste production, and competition between animals and human for crops, a study on the effects of different by-products for Hermetia illucens rearing on the chemical composition of larvae and their environmental impact was conducted, even if, according to the European legislation, today the use of insects as feed source is not possible in ruminants. Regarding climate change, okara and brewer’s grains were the most promising substrates: 0.197 and 0.228 kg CO2 eq/kg of larvae fresh weight, respectively. Results from these studies show the importance of adopting a holistic approach for the assessment of GHG emission from milk production. Therefore, any strategy aimed at mitigating CH4 emission of dairy cows must also take into account the possible effect on the other GHGs, as well as the effect on C sequestration. Based on the studies, it could also be worth evaluating novel feed as a new and useful solution for mitigation of GHG emission related to milk production. The thesis highlights essential differences among forage systems and among feed ingredients of cow ration, confirming that there is room for improvement in sustainability of milk production. These issues should be taken into consideration by farmers, technicians and policy makers, considering that sustainability of livestock production will be one of the priorities for humankind in next future.

The livestock sector is facing different challenges, and the demand for higher sustainability seems to be one of the most urgent. This PhD project debated, in particular, the environmental impacts related to ruminant nutrition, focusing on dairy cows, since nutrition is bound tightly to two of the most important sources of impact: enteric CH4 emission and land use change (LUC). Enteric CH4 emission from ruminants represents 29-38% of the total (anthropic + natural) emission of this powerful (21 CO2 equivalent) greenhouse gas. The production of CH4 is a physiological process used by ruminants to discharge the [H] resulting from rumen fermentation. Different strategies can be implemented to mitigate this impact, and they can be roughly grouped into three main categories: animal and feed management, diet formulation, and rumen manipulation. The second issue investigated in the project is the high reliance of European livestock on soybean meal as a protein source for diet formulation. A total of 30 million tonnes of this feedstuff was imported into Europe in 2020. The main countries of origin are in South America (65% of total import), where 20% of soybean meal production was linked with deforestation (and consequently LUC) in the last decades. Clearing these areas means loss of carbon sink and emission of CO2 in the atmosphere. Other feedstuffs, like grain legumes, oilseed meals alternative to soybean, and high quality forages could be considered to provide protein feed with a lower environmental cost. In this context, the PhD project was developed as follows:  To address the problem of CH4 emission, plant essential oils, as modulators of rumen fermentation, were evaluated (Experiment 1). Furthermore, the effect on CH4 emission of different forages in the diet of dairy cows was investigated (Experiment 2). For validation of mitigation strategies and inventory computation of emissions at a national scale, country-specific equations to quantify CH4 emission were evaluated (Experiment 3).  To address the problem of soybean meal environmental impact, soybean silage and responsible soybean meal (not connected with land use change) were evaluated as protein source alternatives to soybean meal in the diet of lactating cows (Experiments 4 and 5). Enteric methane direct emission In the first experiment, Achille moschata essential oil and its main pure components, namely bornyl acetate, camphor, and eucalyptol, were evaluated in an in vitro experiment. The trial comprehended a short-term in vitro incubation (48 h), with 200 mg of compound per L of inoculum, and a long-term one by continuous fermenter (9 d), with 100 mg/L for each compound. In the first incubation, no differences due to the treatments were found for in vitro gas production (on average, 30.4 mL/200 mg DM, P = 0.772 at 24 h and 45.2 mL/200 mg DM, P = 0.545 at 48 h). Camphor and eucalyptol reduced CH4 production when expressed as % of gas production at 48 h (P < 0.05): -7.4% and -7% compared to control. In the second incubation, CH4 was reduced by eucalyptol (-18%, P < 0.05). Regarding volatile fatty acids, the main effects were a decrease of total production for camphor (-19.5%, P < 0.05) and an increase in acetate production at 9 d with bornyl acetate and camphor (+13% and 7.6%, respectively, P < 0.05) compared to control. Total protozoa count was increased compared to the control (on average: +37%, P = 0.006, at 48 h and +48%, P < 0.001, at 9 d) with all the pure compounds tested. In the short-term incubation, all the treatments reduced Bacteroidetes (30.3%, on average, vs. 37.1% of control, P = 0.014) and Firmicutes (26.3%, on average, vs. 30.7% of control, P = 0.031) abundances but increased Proteobacteria (36.0%, on average, vs. 22.5% of control, P = 0.014). In the long-term incubation, eucalyptol increased the genus Ruminococcus abundance (2.60% vs. 1.18% of control, P = 0.011). An adaptation at long time incubation was observed. In particular, considering eucalyptol addition at 9 d incubation, VFA production was reduced (26.8 vs. 33.3 mmol of control, P < 0.05) contrary to the 48 h incubation (P = 0.189). Furthermore, the treatments affected protozoa genera relative abundances at 24 h (increased abundance for Entodinium with all the treatments, P < 0.001, and reduced for Diplodinium, P = 0.001); at 9 d, instead, protozoa genera relative abundances were not affected by the treatment. The additives tested showed potential in reducing CH4 production without compromising the overall fermentation efficiency. A meta-analysis (Experiment 2) investigated the effects on lactation performance and enteric CH4 of the main forage included in the diet. In the dataset, composed of in vivo experiments, four main forage bases were evaluated: corn silage, alfalfa silage, grass silage, and green forage. Cows fed corn, and alfalfa silages had the highest DMI (21.9 and 22.0 kg/d, P < 0.05) and milk yield (29.7 and 30.4 kg/d, P < 0.05). On the opposite, NDF digestibility was highest for grass silage and green forage (67.6% and 73.1%, P < 0.05) than corn and alfalfa silages (51.8% on average). CH4 production was lower (P < 0.05) for green forage (332 g/d) than the silage diets (on average 438 g/d). Instead, corn silage and alfalfa silage gave the lowest CH4 per kg of milk yield (14.2 g/kg and 14.9 g/kg, P < 0.05). Considering CH4 per kg of DMI, the only difference was between corn silage and grass silage (19.7 g/kg vs. 21.3 g/kg respectively for corn and grass silage, P < 0.05). Finally, prediction models for CH4 production were obtained through a step-wise multi regression. In particular, the models for the prediction of: CH4 in g/d (CH4 = - 65.3(±63.7) + 11.6(±1.67) × DMI - 4.47(±1.09) × CP - 0.86(±0.33) × Starch + 2.62(±0.78) × OM digestibility + 30.8(±9.45) × Milk fat) and for CH4 in g/kg of milk yield (CH4/milk yield = - 55.5(±20.1) - 0.37(±0.13) × DMI + 0.18(±0.05) × Total forage inclusion on diet DM - 0.10(±0.04) × Inclusion of the main forage on diet DM + 0.48(±0.21) × OM + 0.14(±0.06) × NDF + 1.98(±0.86) × Milk fat +4.34(±1.66) × Milk protein) showed high precision (R2 = 95.4% and 88.6%, respectively), but the best AIC value (320) was found for the model predicting CH4 in g/kg DMI: CH4/kg DMI = 6.16(±3.89) - 0.36(±0.03) × CP + 0.12(±0.05) ×OM digestibility + 3.77(±0.56) × Milk fat - 3.94(±1.07) × Milk fat yield. A dataset (66 observations in total) of three in vivo experiments conducted in Italy on lactating cows in respiration chambers was built to evaluate IPCC Tier 2 equations to estimate enteric CH4 production (Experiment 3). In the dataset, the CH4 conversion factor (conversion of gross energy intake into enteric CH4 energy) was lowest for a diet based on grass and alfalfa silages (5.05%, P < 0.05), while the others values ranged between 5.41 and 5.92%. On average, energy digestibility was 69.0% across the dataset, but the diet based on hays had a lower value (64.8%, P < 0.05). The IPCC (2019) Tier 2 (conversion factor = 5.7% or 6.1% for diet with NDF concentration < 35% or >35%, respectively; digestible energy = 70%) gave, on average, a value of CH4 production not statistically different from the ones measured in vivo (382 vs. 388 g/d in vivo, P > 0.05). The IPCC (2006) Tier 2 (conversion factor = 6.5%, digestible energy = 70%) over-predicted CH4 emission (428 vs. 388 g/d in vivo, P < 0.05; μ = -1.05). The most precise models were the two considering digestible energy equal to 70% and average values of conversion factor for IPCC (2006) and IPCC (2019) (R = 0.630); the most accurate models was the one considering a conversion factor equal to 5.7% and energy digestibility measured in vivo (Cb = 0.995). Overall, the best performance among the predicting models tested was for the one based on a conversion factor equal to 5.7% and energy digestibility of 70% (CCC = 0.579 and RMPSE = 9.10%). Use of alternative protein source to conventional soybean meal The dietary inclusion of soybean silage in partial replacement of soybean meal for dairy cows was evaluated in vivo in lactating cow diets (Experiment 4). Cows were fed two diets, one with 12.4% of DM from soybean silage in substitution of 35% of the soybean meal of the control diet. The treatment did not affect DMI and milk yield (on average, 23.7 kg/d, P = 0.659, and 33.0 kg/d, P = 0.377, respectively). Cows fed the soybean silage diet had lower milk protein concentration (3.43% vs. 3.55% of the control, P < 0.001) and higher milk urea (30.5 vs. 28.7 mg/dL, P = 0.002). The soybean silage had lower nutrient digestibility than the control: DMD 65.2% vs. 68.6%, OMD 66.4% vs. 69.8%, NDFD 31.5% vs. 38.8% (respectively for soybean silage and control diet; P < 0.001 for all of them). Regarding N balance, cows fed soybean silage excreted more nitrogen in the urines (32.3 % of N intake vs. 28.9%, P = 0.005) and less in the milk (31.3% vs. 32.7%, P =0.003) than the control. When used as a protein source alternative to soybean meal, soybean silage sustained comparable milk production, but NDF digestibility and N use efficiency should be improved. The environmental impact of the use of soybean silage in comparison to a control diet with soybean meal as the main protein source was evaluated through an LCA approach (Experiment 5). In addition, two scenarios were included in the study, considering the two diets mentioned before, but with soybean meal not connected to LUC (responsible soybean meal). Regarding the single forages, soybean silage had higher global warming potential than alfalfa hay (477 vs. 201 kg CO2eq/ton DM), also when this was expressed per tonnes of protein production (2439 and 1034 kg CO2eq/ton CP, respectively), probably due to the lower contribution of the cultivation phase for alfalfa, being a multi-year crop. The scenario with soybean silage reduced the global warming potential per kg of fat and protein corrected milk (1.17 kg CO2eq) compared to the control (1.38 kg CO2eq). Responsible soybean meal reduced the global warming potential per kg of fat and protein corrected milk (1.13 kg CO2eq/kg vs. 1.38 of the scenario with the control diet). Overall, the best result per kg of fat and protein corrected milk was obtained when responsible soybean meal and soybean silage were used in combination (1.01 kg CO2eq). Also, when global warming potential was evaluated per daily fed TMR, the impact was lowest for the scenario with responsible soybean meal (13.4 kg CO2eq/d) due to the lower contribution of soybean meal to the total impact (11% vs. 43% of the control). Therefore, the two alternative protein sources tested should be preferred when considering environmental impact compared to conventional soybean meals.

Variation in animal personality, in other words, behavioural responses consistent within individuals over time and/or across contexts, is predicted to be related to life-history traits, such as growth rate and investment in reproduction. How this translates into relationships between personality and milk production in dairy cows is however scarcely investigated and previous studies are showing contradicting results. To further investigate this relationship, individual consistencies in behaviour were related to milk production in two breeds of dairy cows (Swedish red and white cattle, SRB, and Holstein). Variation was found among the breeds in consistency of behaviours and both SRB and Holstein cows were highly consistent over time in stepping behaviour during milking and frequency of performed abnormal behaviours in home pen. Overall were Holstein cows consistent in more observed behaviours than SRB. Variation in neophobia and responses to social separation were more flexible, both among breeds and over time. Nevertheless, behaviour showed limited relationship with milk production. To conclude, the tests here carried out are useful in describing personality in cows; however, personality showed no relationship with milk production, encouraging future studies to explore this expected relationship further in other breeds and species.

Organic dairying is growing in popularity in New Zealand and the demand for knowledge is ever increasing. Many more farmers are considering organics as an alternative to their current conventional system. However, limited information is available on organic dairying in a New Zealand pastoral situation particularly in relation to its effect on fertility. The New Zealand dairy industry requires the dairy cow to become pregnant every year at the same time to maximise milk production and utilise the high pasture production in spring. A cow requires 40 to 60 days for uterine involution to occur and for resumption of oestrous cycles. It is critical that the cow becomes pregnant within the six to eight week mating period, however, this can be difficult for late calvers or those cows that had or still have a uterine infection, to undergo uterine involution and be successfully mated. These cows will often not become pregnant and as a consequence be culled for infertility. During the first few weeks postpartum, the bacterial composition of the uterus fluctuates as a result of spontaneous contamination, elimination and recontamination. Most cows are able to eliminate these bacteria, however, 10 to 17% of cows are unable to do this. In these cows, the bacteria persist, cause infection and inflammation, and delay uterine involution. The main objective of this present study was to investigate the effect of different management systems (Organic and Conventional) on productivity and reproduction, particularly the process of uterine involution and its relationship with reproductive outcomes. Uterine involution will be studied through the following measurements: cervical diameter as assessed by measurement per rectum, plasma concentrations of glucocorticoids and bacteriology of the uterus. Lactation characteristics: milk yield, cumulative milk yield, milksolids production and somatic cell count will also be investigated. From the results, it can be concluded that Organic cows have reduced milk yield (P=0.05) and milksolids production (P<0.01) through there were no major differences at peak lactation or in the rate of decline after. However, overall somatic cell count was not affected by management system though the Conventional cows had high somatic cell counts in early lactation (P=0.925). Cervical diameter was affected by the management system with the difference between Organic and Conventional cows almost significant (P=0.06). Cortisol concentrations were significantly higher in Organic cows (0.68 ± 0.08 ng/ml) when compared to Conventional cows (0.95 ± 0.06 ng/ml) (P=0.01). Cortisol concentrations decreased over time postpartum (P<0.01). Additionally Organic cows had a shorter interval from calving to AI (P=0.017). However, none of the other reproductive outcomes were affected by management system. Simple correlations established that reproductive outcomes and bacterial counts, reproductive outcomes and cortisol at Day seven, and cortisol and milk production characteristics, were not independent of each other. Aerobic bacterial counts on Day 28 and the interval from calving to AI were found to be significantly correlated (r= 0.615). Stepwise partial regression analysis, plus analysis of variance calculated on the relationships between uterine involution parameters and reproductive outcomes found multiple weak correlations. It found that cervical diameter, and aerobic and anaerobic bacterial counts on Day 28 were significantly correlated with the interval from calving to first AI (P=0.018). The differences in lactation characteristics are related to the lower pasture production on the organic farmlet reducing the maximal potential milk production and the possibly earlier calving dates of the Conventional cows. The differences in bacterial counts and almost significant difference in cervical diameter may be related to the lower cortisol levels and thus suggest that the Organic cows may be less stressed. As stress suppresses the immune system, it may be possible that the higher bacterial counts are indicitative of a less efficient or slightly weakened immune system which takes longer to eliminate bacteria in the uterus; however this is open to conjecture. The shorter interval from calving to AI suggests that Organic cows may be exhibiting oestrus behaviour earlier postpartum or the Conventional cows are having “silent heats” but this difference is possibly related to human factors. The correlation between parameters of uterine involution and interval from calving to AI, and the lower values for uterine involution parameters in Organic cows suggest the possibility of faster uterine involution and this may result in better fertility in the Organic cows. More research needs to be carried out to further investigate the effect of organic dairying on uterine involution and reproduction outcomes but organic dairying at the very least does not negatively impact on uterine involution and fertility.

The negative energy balance experienced by dairy cows in early lactation caused by the lack of trade-off between energy intake (input) and requests for lactogenesis (output) is responsible for the occurrence of metabolic disorders. Blood metabolites are important indicators to monitor nutritional and energy status of the cows, and to detect the presence of metabolic disorders. In particular, the hyperketonemia (HYK) is one of the most frequent and costly metabolic diseases in early-lactation dairy cows, and it is commonly diagnosed through the determination of β-hydroxybutyrate (BHB) concentration in blood. With this background, the overall objectives of the present thesis were: i) to summarise literature results on phenotypic and genetic aspects of BHB concentration in blood and milk of dairy cows; ii) to develop mid-infrared (MIR) spectroscopy prediction models for routine determination of blood metabolites; iii) to describe phenotypic variation of MIR-predicted blood metabolites in Brown Swiss, Holstein-Friesian and Simmental cattle breeds; iv) to assess the genetic variation of blood BHB and nonesterified fatty acids (NEFA) predicted by MIR spectroscopy, and their correlations with milk production and composition traits in early-lactation Italian Holstein dairy cows. Hyperketonemia is an abnormal concentration of circulating ketone bodies in the blood; in particular, concentration of blood BHB ≥ 1.2 mmol/L is commonly recognized as indicator of HYK. In general, HYK impairs health of dairy cows by increasing the risk of the onset of other early-lactation diseases, and it negatively affects reproductive performance. Although the relationship with milk yield is still controversial, HYK has a detrimental effect on milk composition. Costs of HYK are mainly imputable to impaired fertility and milk loss. From a genetic point of view, results from the literature suggested the feasibility of selecting cows with low susceptibility to HYK. Milk is the most promising matrix to monitor HYK, taking advantage of using MIR spectroscopy during routine milk recording. The effectiveness of using routine milk MIR spectra to predict main blood metabolites in early-lactation dairy cows was evaluated. Blood BHB, urea and NEFA were the most predictable traits. Predicted blood BHB showed an improved performance in detecting cows with HYK, compared with commercial calibration equation for milk BHB. Factors associated with the phenotypic variation of MIR-predicted blood metabolites were investigated on a large spectral multi-breed database. Holstein-Friesian cows had the greatest concentration of blood BHB and NEFA, and the lowest blood urea content. Blood BHB and NEFA concentrations generally increased with parity. The greatest BHB concentration was observed in the first 10 days of lactation, except for Simmental cows. From 5 to 35 days in milk, NEFA concentration decreased, whereas urea content increased for all considered breeds. The maximum levels of blood BHB and NEFA concentrations were recorded in spring and early summer. Blood urea generally increased across the year, from spring to winter. Genetic parameters for MIR-predicted blood BHB and NEFA concentrations were estimated. The greatest heritability for both metabolites was assessed in the first 10 days after calving (0.32 for BHB and 0.23 for NEFA), and their genetic correlation varied from 0.50 to 0.60. Moreover, an unfavourable trend of estimated breeding values for both blood BHB and NEFA concentrations across year of birth of the bulls was detected. Genetic correlations of BHB and NEFA with milk yield, somatic cell score, protein, lactose and urea content were similar or at least in the same direction, whereas opposite correlations were observed with fat content and fat-to-protein ratio.

One hundred sixteen third- and fourth-service lactating dairy cows from five cooperating herds were used to compare the pregnancy rate of cows given Gonadotropin Releasing Hormone five minutes following insemination with pregnancy rate of control cows. In addition, milk production level, age at service and days in milk at time of service were used to compare pregnancy rates. Milk production level was expressed as relative value (percent of herd mature equivalent production). There were no differences between treated and untreated control cows in pregnancy rate. In addition, there were no differences between service number (3 or 4), relative value group, age at service, days in milk at time of service, treatment by service, treatment by relative value, service by relative value, age squared and days in milk squared in pregnancy rate.

Master of Science
Department of Animal Science and Industry
Barry Bradford
During the past decades, the dairy industry has been challenged to find alternative approaches in order to feed cows without affecting their performance or increasing production costs. To accomplish these objectives, some options that have been implemented are the inclusion of short chain carbohydrates to replace starch and the addition of synthetic supplements to increase feed efficiency. In order to assess the impact of these strategies, an experiment was conducted to evaluate productive responses of lactating dairy cattle when they received sucrose and/or exogenous amylase in low starch diets. The results indicated that milk production, milk component profile, and feed efficiency were not significantly altered by the use of the enzyme, sucrose inclusion, or the combination of both. Comparing these results with the literature revealed apparent inconsistencies in responses to the inclusion of sugar in dairy rations. For that reason, a meta-analysis was performed to determine the impact of different sugar sources on milk production, and also to evaluate the impact of other dietary factors on response to dietary sugar. The results indicated that dry matter intake responses were significantly (P < 0.05) affected by an interaction between added sugar and dietary forage neutral detergent fiber content, but overall, dry matter intake tended to increase when sugar replaced corn grain in diets. Energy corrected milk was not affected by dietary sugar, but milk production showed a tendency to respond to treatment, dependent on an interaction between added sugar and rumen undegradable protein. In summary, sugar inclusion may promote small increases in dry matter intake, but the impact on milk production is inconsistent; both factors may be influenced by the diet to which sugar is added.

With the removal of milk quotas in Ireland in 2015, for the first time in 30 years, Irish dairy farmers will be able to increase milk production without the necessity to purchase additional milk quota rights. The aim is to increase milk production by 50% by 2020 compared to the 2007 - 2009 average. Increasing milk volume will challenge both farmers and processors alike. Ireland's milk production is characterised by a spring-calving system, to coincide with grass growth. Ireland ability to produce milk cheaply from grazed grass is considered as the main competitive advantage of Irish dairy farming compared to their European counterparts. In the spring and autumn, grass quantity, and/or quality, can be limiting, resulting in the requirement to supplement the diet with concentrates and forages. With the increase in milk production expected in the coming years, there will be increased demand for feed and supplementation in the Irish grass-based system. These supplementary feeds will have different effects on nitrogen utilisation efficiency, which can affect milk protein fractions and nitrogen excretion, which is important from an environmental perspective. Maximising the efficiency with which milk is processed into high-value dairy products is a clear objective for milk processing plants in Ireland. There is limited information on the effect that dairy cow diet has on milk protein components and milk processability. The objective of this thesis is to increase the knowledge that is available on the effect of supplementing spring-calving grazing dairy cows during times of limited grass availability and/or sub-optimal quality on milk production, nutrient use efficiency and milk processability.

Two production trials were conducted for 84 d each. The first with 22 Holstein cows in late lactation. The second with 46 Holstein cows in early lactation. Treatments were C (control) and AO (A. oryzae 3g/d). Diets were for production trial 1 a 1:1 forage: concentrate ratio; for trial 2 was 2:3. Milk production in trial 1 was higher (P > .05) in AO fed cows during the first weeks of the trial. In trial two AO cows consistently produced more milk (P < .03). Rectal temperatures during hot weather (over 35°C) were consistently lower in AO fed cows, though not significant (P > .10). Two digestibility trials followed the production trials. For all digestion trials, Cr₂O₃ was used as digesta marker. In trial one AO tended to increase digestibility of DM (P > .10). In trial two digestibilities of DM, NDF and ADF were higher in AO fed cows (P < .05). Three other trials were conducted with mature Holstein cows fitted with ruminal and duodenal cannulae. The first trial tested two levels of forage (1:2 vs 2:1; forage to concentrate) and C vs AO in a 4x4 latin square design. AO increased (P < .05) ADF digestibility in the high concentrate died. No change (P > .10) in rumen pH, concentrations and proportions of VFA, and ammonia concentrations resulted from AO treatments. In the second trial C, AO and SC (Saccharomyces cerevesiae 3 g/d) were compared in a repeated 3x3 latin square design. A 1:2 forage to concentrate diet was fed to six lactating cows. Both AO and SC increased (P < .05) rumen NDF digestibility. The third trial compared C vs AO in a swithchback design with four lactating cows fed a 2:3 forage to concentrate diet. AO increased (P < .05) rumen fiber digestion. AO did not affect rates of passage of corn or alfalfa hay; or the potentially digestible DM of milo, alfalfa hay or wheat straw. AO did increase (P < .05) digestion rate of alfalfa DM. In vitro AO increased DM digestibility. That effect can be reproduced by incorporation of the additive at the time of inoculation.

Afin de répondre à la diversification des objectifs de la filière laitière (ex. efficacité alimentaire, santé et longévité des animaux, etc.), et ceci dans un contexte de forte volatilité des prix du lait et des intrants, la quantification des réponses multiples aux changements de régimes alimentaires représente un intérêt afin d’aider les producteurs laitiers à optimiser la ration des animaux. Le principal objectif de ce travail a consisté à développer et évaluer un modèle de prédiction des réponses de l’ingestion, de la quantité et composition du lait aux changements de régimes alimentaires chez la vache laitière. Une méta-analyse a ainsi été appliquée sur une grande base de données de la littérature afin de quantifier la réponse de l’ingestion aux régimes, et les réponses laitières (quantité totale, sécrétion des composants du lait et composition du lait) aux changements d’énergie nette (UFL) et protéines métabolisables (PDI) de la ration. Un élément clé dans le développement de ces équations de réponses était qu’elles soient applicables à travers différent potentiel laitier. Ceci a pu être atteint en exprimant les apports PDI et UFL par rapport à une situation nutritionnel pivot, qui correspond à une efficacité d’utilisation des PDI de 67% et une efficacité d’utilisation des UFL par lait de 100% (équivalente à un bilan énergétique nul). Construite à partir des efficacités PDI et UFL, une approche a été proposée pour estimer les apports PDI et UFL à la situation pivot, à partir desquels les équations de réponses peuvent s’appliquer. Evalué sur deux jeux de données indépendants, cette approche a permis de prédire les réponses de production laitière, productions de matières grasses, lactose et protéines du lait aux changements d’apports PDI et UFL avec une bonne précision pour des rations considérablement différentes, et à travers différents stades de lactation. Dans un autre modèle, les effets du stade physiologique (stade de lactation, stade de gestation, croissance) sur les performances animal, i.e. production laitière, productions de matières grasses, lactose et protéines du lait, changement de composition corporelle et ingestion, ont été quantifiés à travers des animaux de potentiel laitier différent. Il a été constaté que la structure du modèle était adéquate pour simuler les performances de différentes races laitières (Holstein, Rouge Danoise et Jersiaise). Afin de prédire les conséquences d’un changement alimentaire sur le long terme, les équations de réponses, centrées sur la situation nutritionnel pivot, ont été intégrées au sein du modèle dynamique. Cette intégration a pu se faire en appliquant le concept du pivot au modèle dynamique afin d’obtenir des courbes pivot, à partir desquelles les lois de réponses s’appliquent. Le modèle construit est le premier à intégrer les deux grands types de régulation biologique (homéostase et l’homéorhèse) chez la vaches laitière permettant de prédire les performances animales à partir d’une définition précise du potentiel laitier
In order to better cope with the increasing diversity of objective in dairy production (e.g. feed efficiency, animal health, animal longevity, etc.) in a context of high volatility of feed and milk prices, quantification of animal’s multiple responses to dietary changes is of particular interest to help dairy farmers in optimizing the diet. The main aim of the present study was to develop and evaluate a model to predict the responses in dry-matter intake, milk yield, milk component yields and contents to changes in dietary composition in dairy cows. A meta-analysis of the literature was conducted to quantify dry-matter intake response to changes in diet composition, and milk responses (yield, milk component yields and milk composition) to changes in dietary net energy (NEL) and metabolizable protein (MP) in dairy cows. A key point in the development of these response equations was that they could be apply on animals of varying production potential. This was achieved by expressing MP and NEL supply relative to a pivot nutritional status, defined as the supply of MP and NEL resulting to MP efficiency of 0.67 and NEL efficiency of 1. Based on MP and NEL efficiency, an approach was proposed to estimate the pivot MP and NEL supplies, around which the response equations can be applied. Evaluated with two independent datasets, this approach predicted milk yield and milk component yields responses to change in MP and NEL supply with a good accuracy for diets that are substantially different, and across all stages of lactation. In another model, the effect of physiological status (lactation stage, gestation, growth) on animal performance, i.e. milk yield, milk component yields, body composition change and dry-matter intake, were quantified across a range of animal potential. It was found that the model structure was adequate to simulate performance of different dairy breeds (Holstein, Danish Red and Jersey). To predict the long-term consequences of a dietary change, response equations, centred on the pivot nutritional status, were integrated into the dynamic model. This integration has been possible by applying the pivot concept into the dynamic model. This way, lactation pivot curves were calculated, from which response equations are applied. The model built is the first to integrate the two major biological regulations (homeostasis and homeorhesis) in dairy cows that predicts animal performance using a precise definition of milk potential

Three non-lactating Holstein cows fitted with rumen cannula were used to determine crude protein and dry matter rate of disappearance of two protein supplements: 1) soybean meal and 2) bypass protein blend by using the in situ bag technique. Rate disappearance (%/hr) was higher for soybean meal. Two collection periods were completed using 6 cows with a minimum of 21 d adaptation to the treatment top dressed on to the total mixed ration. Ruminal concentration of ammonia N, blood ammonia, and urea did not differ between treatments. Total concentration of volatile fatty acids was higher for bypass protein blend-fed cattle as well as percent molar concentration of propionate, butyrate, and valerate, while pH was lower. Total protozoa, and total and cellulolytic viable bacteria populations did not differ. Four of the cows received a dose of 5 ml of Prostaglandin F,a. Blood and cervical muc us samples obtained showed no difference in blood ammonia and urea concentration . Forty-six Holstein cows were assigned to one of the two treatments (top dressed on the t otal mixed ration), according to parity during the following 125 d postpartum. Daily dry matter intake and milk production were recorded. Feed, orts, and feces were sampled. Milk samples were collected weekly and analyzed for components. Percent lactose and solid non-fat showed higher for cattle fed the bypass prorein blend. Starting on day 10 postpartum, cows were observed for signs of estrus and bred at first estrus observed after 45 d postpartum. Cervical mucus and blood collected at first standing estrus, and first, seco nd, and third service, did not show a significant difference in urea concentration between rations. Twice-weekly collected blood samples showed similar monthly mean concentration of ammonia, urea, and progesterone profile for both treatment groups. Percent pregnancy, services per pregnancy, first service pregnancy and embryo mortality showed no significant difference. Motility and survivability of bull sperm were evaluated by incubating thawed semen in different levels of previously observed and/or ammonia. physiological There were no concentrations of urea significant treatment differences observed. Detrimental effects of treatment on sperm were not detected.

Crossbreeding programs in dairy cattle currently stand as a viable alternative in the dairy industry, because they may alleviate problems related to elevated homozygosis, which has occurred as a result of intensive selection programs using pure breeds. The data utilized of the set of analysis presented hereby, was collected from four commercial dairy farms located in northern Italy between 2007 and 2013. All the farms had a common management system and were using the same 3-way rotational crossbreeding program, including Holstein(HO), Montbeliarde(MO), Swedish Red (SR). The farmers were using also 2-way rotational crossbreeding program, including Holstein(HO) and Brown Swiss (BS). The most common reason for the interest in the use of cross breeding programs by dairy producers is the need to improve cow fertility, health and survival, traits that have progressively deteriorated during the last few decades. A common index used for the evaluation of fertility is the interval between calving and conception, more commonly known as days open. The reproductive performance of crossbred cows has been evaluated by many authors. However, many of these studies reported a value of days open truncated at 250 d. This approach could reduce fertility differences between breed groups. Therefore, the availability of time related variables, such as days open, are influenced by culling time of the cow and by the time of data collection. Data from those cows for which the insemination event, or the conception, have not occurred by the time of culling or data recording, are missed, which leads to some bias on fertility parameters. The objective of the second chapter was to investigate the effect of crossbreeding on fertility traits, studying reproduction time interval traits through survival analysis and success traits and inseminations to conception through logistic regression of heifers and primiparous cows. Results from both cows and heifers suggested that crossbreeding can improve fertility of purebred dairy herds. Crossbred animals showed early insemination after calving and also became pregnant before purebred Holstein cows. Crossbred cows showed a higher probability to conceive at the first insemination, and required less inseminations to achieve conception. The favorable effect in heifers was less pronounced than in primiparous cows. Differences in milk yield between pure HO cows and crossbreds has been well characterized, however the information available on milk lactation curves of crossbred cows, such as peak yield, time at peak, and persistency, is less abundant. The objective of chapter 3 was to evaluate milk curve parameter of primiparous HO and crossbreds cows, using Wilmink function (1987) and modified Wilmink function , in order to include the effect of pregnancy. Milk lactation curves parameters showed different values between pure HO and crossbred cows. Holsteins showed a higher level of production than all crossbred cows. On the contrary, the increase in milk yield towards the peak was not different between pure HO and crossbreeds. Some crossbreeds showed a difference in the persistency of the lactation The effect of pregnancy on milk production was lower for MO × HO and MO ×( SR × HO) crossbreds cows than for pure Holstein, but the gestation started to affect milk production earlier for these two crossbreds. The use of pregnancy on the model showed a general increase of the accuracy of milk production prediction after the milk peak, relative to the classic Wilmink model. The effect of pregnancy is also reported to had an effect as well on milk yield, as on milk component. Furthermore, as reported before, crossbreds cows showed higher reproductive ability then pure HO, and became pregnant before, so that the effect of gestation on the production start earlier in the lactation than for pure Holsteins. The aim of chapter 4 was to compare milk production and milk components of pure HO and crossbred cows, accounting for the effect of pregnancy stage in the model. Pure HO cows showed higher milk yield than all the crossbreds cows. The superiority of HO for yield traits was found also for protein and fat yield, which were higher for HO cows than all crossbreeds, except for BS × HO crossbreds that showed not differences in these traits, when compared with pure HO. However, this inferiority in production was accompanied by a higher milk quality for crossbreds cows. All crossbreds showed higher protein content than pure HO cows and SR × HO crossbred s cows showed also higher fat content than pure HO. Lower values of SCS were reported for SR × HO and BS × HO crossbreds cows, compared with pure HO. Whether the benefit from increased fat and protein content in milk can offset a reduced yield of milk and milk components will depend on specific pay systems. The marketing of cheese has grown in recent years, and cheese plays an important role in the economics of dairy production. So that is important to consider the quality of milk not only in terms of protein and fat content, but also to consider the aptitude of milk to be transformed into cheese. The objective of the last chapter was to evaluate the effect of crossbreeding on milk quality traits, traditional milk coagulation properties and curd firmness model obtained from individual milk samples. Relative to pure HO, the crossbreds used in our study showed more desirable MCP, showed a faster coagulation time and higher curd firmness values. Furthermore, differences between crossbreds for these parameters were also found. Our results suggest that the use of crossbred animals can impact milk yield, milk composition and its MCP. Depending on the intended use of milk, different types of sires can be chosen to direct the efforts of farm crossbreeding programs.
L’uso di un piano di incrocio fra vacche da latte risulta essere una valida alternative per gli allevamenti, in quanto può aiutare ad alleviare problemi dovuti all’elevata omozigosi, causata da una spinta selezione nelle razze in purezza. I dati utilizzati per questa tesi sono stati raccolti in quattro diversi allevamenti in nord Italia, e riguardano animali presenti in azienda tra 2007 e il 2013. Gli allevamenti avevano in comune lo stesso tipo di programma di gestione aziendale e utilizzavano lo stesso programma di incrosio a rotazione a tre vie, con razze Holstein (HO), Swedish Red (SR) e Montbeliarde.(MO) Inoltre, negli allevamenti erano anche presenti incroci ottenuti con l’uso di razza Bruna Alpina.(BS). La ragione più comuni per la quale gli allevatori si interessano a piani di incrocio fra razze da latte, è la necessità di migliorare la fertilità, la salute e la sopravvivenza degli animali in allevamento. Un comune indice usato per valutare la fertilità è l’intervallo parto-concepimento, comunemente chiamato anche days open. Le performance riproduttive degli incroci sono state valutate da diversi autori. Molti di questi studi utilizzano però un analisi che stabilisce un limite massimo di 250 giorni di days open, e questo tipo di approccio può ridurre le differenze fra gli incroci e gli animali puri. Inoltre, la disponibilità di variabili temporali, come i days open, sono influenzate dal momento in cui l’animale viene eliminato e dal momento in cui avviene la raccolta dati. Tutti quegli animali per i quali non c’è stata un ’inseminazione, o un parto, al momento dell’eliminazione dell’animale, o della raccolta dati, non vengono considerati nell’analisi, il che può portare qualche bais nella valutazione dei parametri legati alla fertilità. L’obiettivo del secondo capitolo era quello di valutare l’effetto del crossbreeding sui caratteri legati alla fertilità di manze e vacche primipare, analizzando i caratteri di tipo temporale tramite analisi di sopravvivenza, e caratteri di tipo successo/non successo e numero di inseminazioni, tramite analisi di regressione logistica. .I risultati, sia per le manze che per le primipare, mostrano che gli incroci possono aumentare la fertilità a livello aziendale. Gli animali meticci hanno infatti mostrato migliori risultati sia per l’intercallo parto-prima inseminazione, che per l’intercallo parto-concepimento, e a questi animali è stata inoltre attribuita una più alta probabilità di concepire alla prima inseminazione e un numero inferiore di inseminazioni per concepimento. L’effetto favorevole degli incroci è risultato più pronunciato nelle primipare, che nelle manze. La differenza in termini di produzione di latte fra HO ed incroci è stata ben caratterizzata, ma le informazione sul tipo di curve di lattazione degli incroci, come il picco di lattazione, il momento in qui questo avviene e la persistenza, sono meno numerose. L’obiettivo del capitolo 3 è stato quello di valutare i parametri relativi alle curve di lattazione di vacche primipare HO e dei relativi incroci, utilizzando la classica funzione descritta da Wilmink (1987) ed una funzione modificata, nella quale è stato considerato anche l’effetto della gravidanza. Il livello di produzione di latte è risultato essere più alto per le HO, rispetto a tutti gli incroci, mentre il parametro che descrive l’incremento verso il picco, non ha evidenziato particolati differenze fra incroci e vacche pure. Per la persistenza della lattazione sono state trovate alcune differenze fra gli animali puri e gli incroci. Inoltre, l’effetto della gravidanza sulla produzione di latte è risultata essere inferiore per gli incroci MO × HO e MO ×(SR × HO) rispetto agli animali puri, ma l’effetto significativo della gestazione sulla produzione per questi due incroci iniziava prima che per le HO. Il modello che tiene conto della gravidanza ha mostrato una miglior capacità predittiva per il latte dopo il picco, rispetto alla classica funzione di Wilmink. Oltre ad avere un effetto sui parametri relativi alla curva di lattazione, la gravidanza influisce anche sulla produzione di latte e dei suoi componenti, sia in termini quantitativi che percentuali. Inoltre, come riportato in precedenza, gli incroci hanno dimostrato migliori performance riproduttive, rimanendo gravide prima rispetto alle vacche HO. L’effetto della gestazione sulla produzione inizia quindi in una fase della lattazione precedente per gli incroci. L’obbiettivo del capitolo 4 era quello di comparare vacche HO con relativi incroci per la produzione e la composizione del latte, considerando nel modello l’effetto della gravidanza. Le HO hanno mostrato una produzione di latte più alta rispetto a tutti gli incroci ed anche la quantità di grasso e proteina prodotti è risultata maggiore per gli animali puri, ad eccezione dell’incrocio BS × HO , che non ha mostrato differenze significative in termini di produzione grasso e proteina rispetto alle HO in purezza. Se le HO sono risultate superiori in termini quantitativi, gli incroci si sono dimostrati migliori per i parametri qualitativi. La percentuale di proteina era più alto per tutti gli incroci rispetto agli animali in purezza,. e gli incroci SR × HO hanno mostrato anche un maggior contenuto di grasso nel latte. Inoltre, sia gli incroci SR × HO , che quelli BS × HO, avevano un più basso valore di SCS, rispetto alle HO. Gli incroci hanno quindi mostrato una produzione inferiore rispetto agli animali puri, ma posso incrementare la qualità del latte, soprattutto in termini di proteina percentuale, il che, in alcuni sistemi di pagamento del latte, può avere anche un riscontro economico. Il mercato legato alla produzione di formaggio è stato caratterizzato da un incremento negli ultimi anni, ed il mercato del formaggio riveste un ruolo economico importante nel mercato del latte. Parlando di qualità del latte non è quindi importante parlare solo di contenuto in grasso e proteina, ma anche dell’attitudine casearia del latte. L’obiettivo del capitolo 5 era quello di valutare l’effetto del crossbreeding sulla qualità del lattee sulle proprietà coagulative del latte, utilizzando dati ottenuti da analisi su latte individuale.

Forty high producing early to mid lactation Holstein cows were blocked according to stage of lactation and previous two-week milk yield (experiment 1) . Eight ruminally and duodenally cannulated nonlactating Holstein cows were used for experiment 2. The objective was to determine the effects of the ration's high fat content (11.53%) when rumen degradable or rumen undegradable protein is fed with or without added niacin. Cows received one of five treatments: 1) basal ration (TMR); 2) basal ration with added rumen undegradable fat (RUF) (1.6 kg); soybean meal (SBM) (1.73 kg), and niacin (12 g); 3) same as treatment 2, without niacin; 4) same as treatment 2 but replacing the soybean meal with undegradable protein (UIP) (1.9 kg ) ; and 5) same as treatment 4, without niacin. Rations and water were offered ad-libitum for 10 weeks. Intake for experiment 2 was limited to 18 kg TMR, 0 .76 kg RUF, 0 .88 kg SBM or UIP, and 6 g niacin. All cows in experiment 2 received the five treatments by the end of five collection periods separated by 21 d adaption. RUF increased dry matter intake (22.95 vs. 23 . 72 kg/d ) and mean body weight (607 vs. 637 kg ) , but decreased milk protein, lactose and SNF (proportion and yield); and 4% FCM without affecting daily milk yield. RUF, SBM, and N did not affect milk production. Milk protein percentage, protein yield, lactose percentage, SNF percentage, and yield were decreased by UIP supplementation. Niacin had a negative effect on milk fat percentage and yield, and milk protein percentage when fed with RUF and UIP . Supplements did not affect milk protein components. RUF increased plasma glucose (56.8 vs. 63.5). RUF addition increased AD and ND digestibility while decreased fatty acid digestibility. UIP improved ND digestibility in the lactation trial. For experiment 2, UIP increased rumen propionate percentage, thus reducing acetate to propionate ratio. Niacin increased total VFA production (128.6 vs. 114.3 umol/ml) . RUF, UIP, and niacin increased total bacterial population. RUF reduced cellulolytic bacteria in rumen fluid. Nutrient rate of passage and digestibility were unaffected by treatments except for dry matter and RUF digestibility that were reduced by RUF supplementation.

Twenty-two primiparous Holstein heifers were allocated to one of two treatments. Treatments consisted of: l) basal ration plus 226.8 g inorganic mineral supplement (control); and 2) basal ration plus 226.8 g inorganic mineral and metal proteinate supplement (50:50). Individual heifer performance was measured during the final l 0 weeks of the prepartum period. Feed intake and refusals were recorded daily. Individual heifer body weights recorded weekly did not differ significantly. Blood samples taken at 4-week intervals did not differ in plasma concentration between treatments. Calf birth weights for control heifers were not significantly higher than calves from the treatment heifers. The same twenty-two Holstein heifers used in the prepartum period were assigned to the same treatment groups for the 20-week postpartum lactation period. Treatments consisted of: 1) basal ration plus 453.6 g inorganic mineral supplement (control); and 2) basal ration plus 453.6 g inorganic mineral supplement and metal proteinate supplement (50:50). Dry matter intake and milk yield were recorded daily. Milk composition and body weights were recorded weekly. Feed and fecal samples were collected to determine apparent nutrient digestibility, using acid insoluble ash as an internal marker. Blood samples taken at. 4-week intervals showed no significant difference (Ρ < .05) in plasma mineral composition. No statistical difference was observed in milk yield between treatments (Ρ < .05). Percent lactose in milk samples from the treatment group was significantly higher (Ρ < .05) than that of the control group. Apparent nutrient digestibilities did not differ between treatment groups. Starting on day 5 postpartum, cows were observed for signs of estrus and bred at first observed estrus after 60 days postpartum. Days to first estrus were significantly lower (Ρ< .05) in the treatment group. The feet of each heifer were critically evaluated and scored according to six separate criteria at the start and at the finish of the trial. The texture category of the hoof evaluation score was significantly lower (Ρ < .05), favoring the treatment group over the control group.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O trabalho foi conduzido no Instituto de Zootecnia - Agência Paulista de Tecnologia dos Agronegócios, em Ribeirão Preto. Os tratamentos foram constituídos de quatro dietas experimentais. Dieta I contendo semente de girassol e cana-de-açúcar “in natura”; Dieta II contendo semente de girassol e cana hidrolisada; Dieta III contendo farelo de girassol e cana hidrolisada e Dieta IV contendo óleo de girassol e cana hidrolisada. O período experimental teve duração de 84 dias, composto de três estágios denominados, inicio, meio e fim, de 28 dias cada, sendo os últimos quatro dias utilizados para coleta de dados. Os animais foram distribuídos em um delineamento inteiramente casualizado, composto por quatro tratamentos e seis repetições. A análise estatística dos dados foi realizada utilizando-se o Statistical Analisys System (SAS, 2003). A comparação entre as dietas foi realizada por meio de teste de Tukey. O objetivo deste trabalho constituiu-se em analisar os efeitos da utilização de dietas contendo cana-de-açúcar “in natura” e hidrolisada com Ca(OH)2, associadas a semente, farelo e óleo de girassol na alimentação de vacas mestiças em lactação, sobre os parâmetros metabólicos e fisiológicos, composição do leite e viabilidade econômica. Os tratamentos contendo cana hidrolisada com semente e óleo de girassol apresentaram maiores produções de leite (16,49L e 16,79L). As dietas contendo cana hidrolisada apresentaram maiores teores de Ca. As vacas alimentadas com cana hidrolisada e óleo de girassol apresentaram perfil de gordura no leite de melhor qualidade para consumo. A dieta contendo cana de açúcar hidrolisada e semente de girassol proporcionou maior produção leiteira e melhor receita bruta
The sugar cane is a good food in energy, presents high productivity, is available in the dry season and after the maturation keeps its practically constant the nutritional value. However limitations how the low digestibility of fiber can decrease the voluntary dry matter intake. The alkaline treatment in the sugar-cane with Ca(OH)2 can increase the fiber digestibility good efficiency improvements on its digestibility, but the use of lime has raised questions about high levels of calcium in the diet of lactating cows, which could lead to metabolic diseases and losses productivity. This work consisted in analyzing the effects of diets containing sugarcane ‘in natura” and hydrolyzed with Ca (OH)2, associated with sunflower meal, sunflower oil, sunflower seed in the diet of lactating cows on the metabolic and physiological parameters, milk composition and economic viability. The present research was carried in Institute de Zootecnia at Ribeirão Preto city to evaluate diets with raw and hydrolyzed sugarcane associated with sunflower (seed, meal and oil).The diets were: I- raw plus seed; II – hydrolyzed plus seed; III – hydrolyzed plus meal and IV – hydrolyzed plus oil. The research was conducted in 84 days, with 3 stages of 28 days included 4 last days to collect data. Twenty four dairy cows were distributed in a randomized design with four treatments and 6 repetitions. Means were compared by Tukey

Dissertação de Mestrado Integrado em Medicina Veterinária
As doenças e lesões podais são comuns em explorações leiteiras intensivas. A claudicação resultante destas é uma expressão de dor e de desconforto tendo inúmeros impactos negativos ao nível do bem-estar, produtividade e interação social. Tradicionalmente, a claudicação é detetada pela avaliação visual da locomoção apesar da subjetividade e dificuldade por parte dos produtores em avaliar a sua gravidade. A analgesia surge como complemento ao tratamento tradicional à base do corte terapêutico para controlo da dor e modulação da hiperalgesia. A identificação dos casos e o tratamento precoces são essenciais para uma recuperação bem-sucedida, independentemente do tratamento aplicado. O objetivo deste estudo experimental foi procurar avaliar se há correlação positiva entre a administração de um analgésico, após o corte terapêutico e tratamento curativo de doenças e lesões das úngulas, e o aumento do bem-estar e da produtividade, através da medição da atividade diária e da variação na produção leiteira, respetivamente. Após seleção de animais dentro dos critérios do estudo, estes foram divididos por dois grupos: grupo controlo (n = 23), administração subcutânea de 20 ml de soro fisiológico a 0,9%; e grupo tratamento (n = 20), administração subcutânea de 20 ml de medicamento com carprofeno, após o corte terapêutico e respetivo tratamento curativo. No terceiro dia após o tratamento curativo e analgésico, com auxílio do software da exploração, foram recolhidos os dados referentes à atividade diária e à produção leiteira diária dos 3 dias anteriores e posteriores ao tratamento curativo e analgésico. Uma análise da variância foi efetuada para a relação entre os dois grupos em estudo, assumindo um intervalo de confiança de 95% (p ≤ 0.05). Em relação à atividade diária, a diferença estatística entre os dois grupos foi significativa, obtendo um valor de p = 0.05, que indica efeito do tratamento analgésico sobre o bem-estar animal. No entanto, a variação na produção leiteira não mostrou evidência de haver vantagem da analgesia. Uma terapia multimodal com recurso a AINEs, surge como sugestão para a melhor forma de intervir no tratamento de doenças podais visando o bem-estar animal. Contudo, a prevenção deve continuar a ser a chave para que o impacto da claudicação no bem-estar e produtividade dos animais seja reduzido.
ABSTRACT - Impact of pain caused by foot diseases on the activity and production of dairy cows - Foot diseases and injuries are common in cows from intensive dairy farms. Lameness is an expression of pain and discomfort caused by these lesions and has numerous negative impacts on welfare, productivity and social interaction. Traditionally, lameness is detected by visual assessment of locomotion despite subjectivity and difficulty in assessing severity. Analgesia adds the usual treatment by trimming to control pain and reduce hyperalgesia. Early identification and treatment are essential for successful recovery whichever the treatment applied. The aim of this experimental study was to evaluate whether there is a positive correlation between the administration of an analgesic on curative trimming and treatment of foot diseases, with increased welfare and productivity by measuring daily activity and milk production, respectively. After selection of animals within the study criteria, these were randomized into two groups: control group (n = 23), subcutaneous administration of 20 ml of 0.9% saline; and treatment group (n = 20), subcutaneous administration of 20 ml of carprofen drug after curative trimming and appropriate treatment. On the third day after therapeutic and analgesic treatment, with the aid of the farm´s software, data on daily activity and milk production of the 3 days before and 3 days after treatment, were collected. An analysis of variance was performed for the relationship between the two study groups, assuming a confidence interval of 95% (p ≤ 0.05). Regarding daily activity, the statistical difference between the two groups was significant, with a value of p = 0.05, which indicates the effect of analgesic treatment on animal welfare. However, dairy production showed no evidence of the advantages of analgesia. Multimodal therapy using NSAIDs, arise as a suggestion for the best way to intervene in the treatment of lameness aiming for increased animal welfare. However, prevention should remain the key to reduce the impact of lameness on animal welfare and productivity.
N/A

Effects of a short 40-d dry period with only a close-up diet (SHORT) and a conventional 60-d dry period with a 39-d far-off and a 21-d close-up diet (CONV) on milk production, feed intake, blood and rumen parameters, liver gene expression and rumen microbiota profile were compared in 11 second-parity and 15 third and later parity cows. Milk production was recorded daily during the first 16 wks of lactation. Differential liver gene expression was assessed by affymetrix microarray analysis and DNA extracted from rumen samples was subjected to Illumina sequencing for exploring the microbiome profile. The SHORT treatment reduced milk yield and DMI after calving in third and later parity cows, but not in second-parity cows when compared to the CONV treatment. Cows on the SHORT treatment had higher concentrations of NEFA in blood plasma and tended to have higher liver TAG immediately after calving. These effects tended to be greater in third- and later parity cows compared to second-parity cows. Expression patterns of genes involved in β-oxidation at the first week of lactation compared to those at three weeks before calving showed lower hepatic β-oxidation capacity in cows on the SHORT treatment compared to those on the CONV treatment. During this period, the expression of DGAT, a key gene in the triglyceride synthesis, increased in SHORT-treatment cows while it remained unchanged in CONV-treatment cows. The expression patterns of genes involved in gluconeogenesis showed a higher capacity at first week after calving in cows on the SHORT compared to those on the CONV treatment. Our study also showed that the SHORT treatment increased the relative abundance of Firmicutes and reduced the relative abundance of Bacteroidetes compared to the CONV treatment and reduced the shifting of rumen microbiota from before to after calving. Results also demonstrated that the rumen microbiota was more stable in the SHORT treatment during the transition period. Based on these results, a 40-d dry period management with only a close-up diet might be beneficial for second parity cows. However, this treatment may be detrimental for older cows as excessive energy intake and fat deposition during the dry period in these animals result in lower milk production and higher mobilization of NEFA and accumulation of fat in the liver.
February 2016

Two studies were conducted during the grazing season of 1997. Study 1 consisted of three Experiments, and the objectives were to compare milk production and composition, body weight change and body condition score, and to determine time patterns of grazing between cows supplemented with different forms and amounts of corn. Also rumen fermentation parameters were measured in cows supplemented with two different types of corn. In study 2, milk yield was measured when grazing pasture was supplemented to lactating Holstein cows fed a typical TMR diet. Predominantly orchardgrass pastures with lesser amounts of white clover and Kentucky bluegrass were grazed during both studies. In Experiment 1, 36 Holstein cows were supplemented either with 6, 6, 6, or 4 kg/d DM of high moisture corn, coarsely ground corn, finely ground corn, or high moisture corn in two equal feedings, respectively. Milk yield was similar (30.3 kg/d) among treatments. Milk protein (2.97%) and MUN (14.7 mg/dl) did not differ among treatments. Body weight change and body condition score change were similar among treatments (23.1 kg and -0.24). During Experiment 2, four rumen-cannulated cows in mid-lactation were supplemented 6 kg/d DM of either coarsely ground corn or high moisture corn in two equal feedings. After the p.m. milking, ruminal pH was measured and rumen fluid samples were collected to determine ammonia N and VFA. While grazing, this was repeated at 0.5, 1, 2, 3,...8 h post-corn feeding (0 h). Ruminal pH was similar for both corn supplements and was lowest (5.9 and 5.8) at 5 and 8 h, respectively. Rumen ammonia N concentrations started to increase approximately 2 h after cows began grazing, reaching maximum levels 5 h later. In Experiment 3, the number of cows grazing, lying, or standing were recorded every half hour, for two consecutive days, while grazing. Cows grazed an average of 6.4 h/d, 4.1 h in the afternoon and 2.3 h in the morning. Similarity in milk production, milk composition, BW change, and BCS between treatments indicates that the quality and availability of pasture permitted equal response regardless of the type or amount of corn supplemented. Fifty four Holstein cows in mid lactation were used in Study 2. Cows were fed either a TMR diet only, or were fed TMR during half of the day (after the a.m. or p.m. milking according to the treatment) and supplemented with grazing pasture during the other half of the day. Milk production was slightly but significantly higher for cows on the TMR treatment (29.1 vs. 28.2 and 27.6). No significant difference between treatments was observed in FCM (27.7 kg/d), and milk fat (3.47) and protein percentage (3.23). While BW change did not differ among treatments (25.7 kg), body condition score increased more in cows fed only a TMR diet (0.14 vs. -0.06 and 0.01). The TMR intake was significantly different between treatments, being highest for cows on the TMR treatment and lowest for cows grazing after the p.m. milking (26.6 vs. 20.3 vs. 17.5 kg/d DM). Income over feed cost differed between treatments, and was approximately 15.3% higher for cows supplemented with high quality pasture during the afternoon compared to cows on TMR. Dairy farmers may obtain economical benefits by practicing this type of management during the grazing season with little effect on milk yield.
Master of Science

Bovine somatotropin (bST) is a protein synthesized at the base of the brain and released by the pituitary gland into the circulatory system. BST is transported by the circulatory system and absorbed only by cells of target organs that possess cell surface receptors for the protein (11, 41). Its effect is initiated via a protein receptor initiation and cyclic AMP cascade . This effect on the cell continues well past the degradation of the bST molecule. BST is likely transported into the cell, where it is degraded . Its constituent blocks, amino acids, are used to synthesize new proteins or converted to other metabolites such as sugars (1).

In Brazilian livestock, and its diverse ways of production, the management of grazing animals is known as the lowest return on investment on land use opportunities. Nevertheless, among different types of milk production systems, it is noted that the use of pasture grazing is a common feature between them. Thus, to achieve profitability and maintain system sustainability, the identification of the most adequate and efficient pasture management practices, can maximize production per cow and production per unit area. The low efficiency of this method of production, also classifies the national livestock as the major source of environmental pollution due the emission of pollutants, such as greenhouse gases and nitrogen. The adoption of pasture management techniques respecting forage physiological limits and increasing digestibility of nutrients, can reduce the excretion of nutrients and the production of methane per kilo of milk produced on the environment. The objectives of this thesis were to investigate metabolic variables, greenhouse gas emissions and animal performance for dairy cows grazing elephant grass subjected to rotational stocking strategies. Chapter 1: In this study was to evaluate two strategies of grazing management: pre-grazing targets of 95% versus maximum canopy light interception (LI). In intensive pasture-based milk production systems, the management based on LI95% allows lactating cows to have access to pastures with lower proportion of stems, with higher proportions of young leaves better chemical composition and perform an efficient grazing with lower forage losses. Therefore, the LI95% pasture management strategy results in higher energy intake, higher milk production per cow, higher stocking rates of pasture and higher milk yield per area. Also, the strategy allows the decrease of methane emissions per net energy intake when comparing to management based on LIMax. However, dietary N use efficiency did not increase with this management practice. Chapter 2: The objective of the second study was to evaluate the effects of paddock allocation time (a.m. vs. p.m.) on milk production, ruminal variables and efficiency of N use of mid-lactation dairy cows. In intensive pasture-based milk production systems, allocating cows on new paddocks on p.m. time has no effect on forage intake and milk production of grazing mid-lactation cows. However, the higher content of nonstructural carbohydrate of forage from p.m. pastures increases the yield of microbial protein, decreases milk urea nitrogen and tends to increase the yields of milk protein and milk casein compared to a.m. pastures. Throughout this thesis there were an improvement on nutritive value of forage adopting LI95% as a pre- grazing target and forage grazed at p.m. Therefore, the time of allocation on paddock should be used along with LI95% as fine-tune in intensive pasture-based milk production systems.
No Brasil, a produção animal em pastagens é reconhecida por ser uma atividade pouco competitiva frente a outras oportunidades de uso da terra. Embora sejam inúmeros os tipos de sistemas de produção de leite no Brasil, nota-se que a utilização de pastagens é característica comum. Assim, a identificação de práticas adequadas e eficientes de manejo do pastejo contribuirá com aumento da produção por vaca e por unidade de área, além de contribuir para a sustentabilidade do sistema. A baixa eficiência do uso dos recursos naturais tem classificado a pecuária nacional como uma importante fonte de poluição ambiental devido à emissão de poluentes, como gases de efeito estufa e excreção de nitrogênio. A adoção de técnicas de manejo de pastagens respeitando os limites fisiológicos da forrageira e aumentando sua digestibilidade, podem reduzir a produção de metano por quilo de leite produzido no ambiente e a excreção de nutrientes. Os objetivos desta tese foram investigar variáveis metabólicas e desempenho animal de vacas leiteiras em capim-elefante cv. cameroon submetido a estratégias de pastejo rotativo. Capítulo 1: Neste estudo foram avaliadas duas estratégias de manejo de pastejo: meta de pré-pastejo de 95% versus máxima interceptação luminosa (IL). Em sistemas intensivos de produção de leite à pasto, o manejo baseado no IL95% permite que vacas tenham acesso a pastos com maior relação folha: colmo, menores perdas de forragem, resultando em uma forragem com melhor composição química. Os animais pastejando forragem com IL95% tiveram maior consumo de matéria seca e energia, com maior produção de leite por vaca e taxa de lotação resultando em maior produção de leite por área. Além disso, a estratégia permite a diminuição das emissões de metano por consumo de energia líquida quando comparado a máxima IL. No entanto, a eficiência do uso de N não aumentou com essa prática de manejo. Capítulo 2: O objetivo do segundo estudo foi avaliar os efeitos do período de início pastejo (a.m. ou. p.m.) na produção de leite, variáveis ruminais e eficiência de uso de N de vacas leiteiras no terço médio da lactação. Em sistemas intensivos de produção de leite à pasto, o pastejo de novos piquetes no período da tarde não teve efeito sobre o consumo de forragem e produção de leite de vacas no terço médio da lactação. No entanto, o maior teor de carboidratos não fibrosos da forragem ao final do dia possibilitou o aumento da síntese de proteína microbiana, redução do nitrogênio uréico no leite e apresentou tendência para aumento da produção de proteína e caseína do leite em comparação à vacas que iniciaram o pastejo no período da manhã. Ao longo dos estudos desta tese houve uma melhora no valor nutritivo da forragem adotando IL95% e da forragem pastejada no período da tarde. Assim, o pastejo no período da tarde deve ser adotado juntamente com IL95% como ajuste fino em sistemas intensivos de produção de leite à base de pasto.

Dairy cows are extremely inefficient at converting dietary nitrogen (N) to productive N. Approximately 25-30% of dietary N is used for milk protein while the remaining N is lost to the environment. According to National Research Council (NRC, 2001) recommendations, dairy cow rations are formulated in terms of metabolizable protein (MP) which often causes many amino acids (AA) to be fed in excess. A better understanding of protein and AA requirements could help to improve the nitrogen efficiency of dairy cows. The objective of this work was to examine the effects of feeding a low protein diet supplemented with rumen protected (RP) AA on production and N efficiency of dairy cows. Twenty-four Holstein and 24 Holstein x Jersey crossbred cows were used in a Youden square design consisting of 3 periods. Cows were randomly assigned to one of 8 treatments: 1) a standard diet containing 17% crude protein (+Con), 2) a 15% crude protein diet (-Con), 3) â Con plus RP methionine (+M, 16g/d), 4) â Con plus RP lysine (+K, 47g/d), 5) â Con plus RP leucine (+L, 181g/d), 6) â Con plus RP methionine and lysine (+MK), 7) â Con plus RP methionine and leucine (+ML), and 8) â Con plus RP methionine, lysine, and leucine (+MKL). Cows fed the â Con as well as the +MKL diet experienced a reduction in milk production and milk protein yield (P < 0.05). Dry matter intake decreased only for those animals on the +ML diet (P < 0.05). Milk urea N (MUN) decreased for all diets when compared to the +Con treatment (P < 0.05). In accordance with the decrease in MUN, N efficiency was numerically increased in the diets supplemented with RP AA, but this improvement was not significant. Phosphorylation of signaling proteins important for protein synthesis were also examined. Animals fed the +MK treatment increased phosphorylated and total forms of eukaryotic elongation factor 2 (eEF2) when compared to the +Con and â Con (P < 0.05), but this increase in abundance did not affect the ratio of phosphorylated to total abundance. Feeding dairy cows a low protein diet supplemented with RP AA has the ability to alleviate the loss in milk production associated with feeding a low protein diet as well as to increase nitrogen efficiency.
Master of Science

Dairy cows are often mixed into new social groups for management reasons, but this is recognized as a cause of social stress. The objectives of this study were to investigate the effect of regrouping on social behaviour, self-licking and milk production of mid-lactation cows introduced in pairs, and to see whether individual variation in aggression is consistent before and after regrouping. In 7 replications (n=7), 14 mid-lactation cows were introduced in pairs into an established group of filler (resident) cows. After regrouping, agonistic contacts and displacement of the introduced cows increased during the first 3 and 2 days, respectively. Compared to baseline (the day before regrouping), the number of social licking events between the introduced cows and the resident cows in the pen did not change after regrouping, but the proportion of social licking between the two introduced cows increased sharply after regrouping (38 ± 9 %) compared to baseline (10 ± 9 %). Duration of social licking decreased declined after regrouping; whereas, self-licking increased on the day of regrouping. Compared to the resident cows, milk production of the introduced cows significantly decreased on the first 2 days after regrouping, and showed a negative linear association with agonistic contacts received and with displacements lost. Two measures of aggressive behaviour (proportion of agonistic contact initiated and proportion of displacements won) were relatively consistent before and after regrouping (R² = 0.75 and 0.68 respectively), suggesting that the differences reflected individual differences in aggressiveness, rather than social status within a given group. In the present experiment, low-and high-aggressive individuals were not different in milk production, social licking and age at first calving, but low-aggressive cows had higher 305-day projected milk production (12,928.0 ± 580 kg) than high-aggressive cows (10,530.0 ± 530 kg). Individual variation in aggression was not associated with body weight, although the heaviest cow in the group won all encounters before and after regrouping. The findings of this study provide the first insights that introducing cows in pairs may mitigate the effects of social stress during mixing.

Three studies were conducted to determine the effects of roasting on ruminal degradability of sunflower seeds and the effects of feeding roasted sunflower seeds on ruminal fermentation, nutrient digestibility and milk yield and composition of dairy cows. Experimental treatments were a control diet with no added sunflower seed, a raw sunflower seed diet and a roasted sunflower seed diet. Sunflower seed diets contained 6% fat whereas the control diet contained 3% fat. In study one, two ruminally fistulated cows were used in a randomized complete block design to determine the effects of roasting on ruminal degradation of sunflower seeds. In the second study, three ruminally cannulated lactating Holstein cows were used in a 3 x 3 Latin square experiment to determine the effects of dietary treatments on ruminal fermentation and total tract nutrient utilization. In the last study, three primiparous and six multiparous Holstein cows were used in three 3 x 3 Latin squares to determine the effects of dietary treatments on milk yield and composition.