Dissertations / Theses on the topic 'Enteric methane emission'

Master of Science
Department of Biological and Agricultural Engineering
Zifei Liu
This study reviewed state-of-the-art cattle enteric methane (CH4) emissions with three reported measuring units: g/head/d, g/kg DMI (dry matter intake), and %GEI (gross energy intake). Cattle emissions studies included in this meta-analysis were reported from 1995 to 2013. Fifty-five published studies were analyzed with specific objectives: (1) to gain basic information regarding magnitudes and distributions of enteric CH4 emission rates with various units, regions, cattle types and feed situations; (2) to identify and evaluate effects of influence factors or diet mitigation techniques on enteric CH4 emissions; and (3) to evaluate Intergovernmental Panel on Climate Change (IPCC) approaches to estimate enteric CH4 emissions. Emissions data (n=165) with the unit of g/head/d had large variances and non-normal distribution, and were not homogeneous across the studies. Emissions data (n=134) with the unit of g/kg DMI were not homogeneous across the studies, while emissions data (n=76) with the unit of %GEI had small variances and normal distribution, and were homogeneous across the studies. Therefore, data with the unit of %GEI may be better for meta-analysis compared to data with the units of g/head/d and g/kg DMI; however, the number of data with the unit of %GEI was small relative to the number of data with the units of g/head/d and g/kg DMI. Enteric CH4 emissions with the unit of g/head/d are significantly influenced by geographic region, cattle classification, sub-classification, humidity, temperature, body weight, and feed intake. Emissions and feed intake had a strong positive linear relationship with R2 of 0.75 (n=148). Emissions with the unit of g/kg DMI are significantly affected by humidity, body weight, and feed intake. The relationship between emissions and feed intake is positive. Emissions with the unit of %GEI are significantly associated with humidity, production stage, and body weight. IPCC Tier 1 and Tier 2 estimated emissions were approximate to most of the measured enteric CH4 emissions; however, the residuals were not normally distributed. Based on results from PRD method and paired t-tests, IPCC Tier 1 overestimated emissions in Asian studies, underestimated emissions in European studies for beef cattle, and underestimated emissions in Oceanian studies for dairy cattle. IPCC Tier 2 underestimated emissions in Asian studies for beef cattle. The underestimated emissions of IPCC Tier 2 in Asian studies might result from no consideration of effects from production stage and body weight.

Mathematical modeling in animal agriculture can be applied at various levels including at the tissue, organ, animal, farm, regional and global levels. The purposes of this research were i) to evaluate models used to estimate volatile fatty acid (VFA) and methane (CH4) production and assess their impact on regional enteric CH4 inventory, and ii) to develop a process-based, whole-farm model to estimate net farm GHG emissions. In the first study, four VFA stoichiometric models were evaluated for their prediction accuracy of rumen VFA and enteric CH4 production. Comparison of measured and model predicted values demonstrated that predictive capacity of the VFA models varied with respect to the type of VFA in rumen fluid which impacted estimated enteric CH4 production. Moving to a larger scale assessment, we examined the enteric CH4 inventory from Manitoba beef cattle (from 1990 to 2008) using two mechanistic rumen models that incorporate VFA stoichiometric models: COWPOLL and MOLLY, and two empirical models: Intergovernmental Panel on Climate Change (IPCC) Tier 2 and a nonlinear equation (Ellis). The estimated absolute enteric CH4 production varied among models (7 to 63%) indicating that estimates of GHG inventory depend on model selection. This is an important consideration if the values are to be used for management and/or policy-related decisions. Development of models at the individual farm component level (animal, soil, crop) does not accurately reflect net GHG emissions generated from the whole production system. We developed a process-based, whole-farm model (Integrated Components Model, ICM), using the existing farm component models COWPOLL, manure-DNDC and some aspects of IPCC to integrate farm components and their associated GHG emissions. Estimates of total farm GHG emissions and their relative contribution using the ICM were comparable to estimates using two other whole-farm models (Integrated Farm System Model and Holos model). Variation was observed among models both in estimating whole-farm GHG emissions and the relative contribution of the different sources in the production system. Overall, whole-farm models are required to explore management options that will mitigate GHG emissions and promote best management practices. However, for full assessment of the production system, other benefits of the system (e.g., carbon sequestration, ecosystem services), which are not part of current whole-farm models, must be considered.

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.

Globally agriculture and livestock producers have come under increasing pressure over the environmental impact of production systems. The objectives of this study were to re-calculate the direct methane (CH4) and nitrous oxide (N2O) emissions of livestock production systems in South Africa, taking into consideration the uniqueness of the South African scenario and to identify and evaluate possible greenhouse gas mitigation strategies for extensive production systems. It is important to generate accurate greenhouse gas (GHG) baseline figures to develop South Africa’s capacity to understand and reduce GHG emissions emitted from the livestock sector. Livestock produce GHG’s in the form of methane from enteric fermentation and nitrous oxide and methane from manure management and manure deposited on pastures and rangeland by grazing animals. Agriculture, forestry and land use (corrected for carbon sink values) emitted an estimated 4.9% of South African GHG gases in 2004, which makes it the third largest GHG contributor in South Africa after the energy industry and industrial processes. Livestock produced approximately 27% of the national methane emissions and 98% of the agricultural sector’s methane emissions in 2004. Methane is a potent GHG that remains in the atmosphere for approximately 9 to 15 years and is 28 times more effective in trapping heat in the atmosphere than carbon dioxide (CO2) over a 100-year period. Nitrous oxide has an atmospheric lifetime of 150 years and a global warming potential of 265 times that of CO2 over a 100-year period. South African livestock production is based on a unique combination of commercial (intensive and extensive) and emerging and communal (subsistence) production systems. The levels of productivity and efficiency in these production systems vary greatly in certain areas and it is important to distinguish between them when calculating GHG emissions. Previous inventories were conducted on a national scale utilizing IPCC default values (Tier 1 approach) for some or all of the emission calculations. These emission factors do not distinguish effectively between classes of animals, production efficiencies, and production systems. They are often based on assumptions of animals utilizing diets which are not representative of South African production systems. The IPCC Tier 2 methodology seeks to define animals, animal productivity, diet quality and management circumstances to support a more accurate estimate of feed intake for use in estimating methane production from enteric fermentation. It was also considered important to do separate calculations for each province as provinces differ in vegetation or biomes and production systems which may require different approaches to mitigation recommendations. Due to the heterogeneity of available feed types within South Africa it was considered important to use methodologies that could reflect such differences and was developed under similar conditions. The methodology utilized is based on the Australian national greenhouse account’s National Inventory Report, which contains Australian country-specific and IPCC default methodologies and emission factors. Emission factors specific to South African conditions and management systems were calculated where possible. A Tier 2 approach was adopted for all major livestock categories including privately owned game in accordance with the IPCC Good Practice requirements. Recently game farming has become a recognized commercial enterprise in the agricultural sector which needs to be included as an anthropogenic emissions source. Methane emissions from South African livestock were estimated at 1328 Giga gram (Gg) during 2010. Dairy and beef cattle contributed an estimated 964 Gg or 72.6% of the total livestock methane emissions in South Africa during 2010. Beef cattle in extensive systems were the largest contributor (83.3%), followed by dairy cattle (13.5%), and feedlot cattle (3.2%). The estimated direct enteric methane emission factors for dairy and beef cattle were higher than the IPCC default factors for Africa. The Eastern Cape recorded the highest dairy and beef cattle methane emissions, whereas Gauteng showed the highest feedlot methane emissions primarily due to cattle numbers. Small stock was responsible for 15.6% of the total livestock emissions contributing an estimated 207.7 Gg, with sheep producing 167 Gg and goats producing 40.7 Gg. Calculated enteric methane emission factors for both commercial and communal sheep were higher than the IPCC default values for developing countries. A similar tendency was found with goat emission factors. The highest sheep and goat methane emissions were reported for the Eastern Cape province. The pig and ostrich industry both contributed approximately 8 Gg CH4 during 2010. The North- West province produced the highest commercial pig GHG emissions with the highest communal pig emissions originating from the Eastern Cape. The poultry industry was the largest direct N2O producer of the non-ruminant livestock industries, contributing 2.3 Gg or 92.8% of the total nonruminant N2O emissions. The privately owned game industry contributed an estimated 131.9 Gg of methane emissions with the provinces of Limpopo, Eastern Cape and Northern Cape being the three largest contributors with 43.4, 37.3 and 21 Gg methane, respectively. The total privately owned game population was estimated at 2 991 370 animals, utilizing 20.5 million hectares. Beef cattle are the major contributors to livestock GHG emissions in South Africa followed by sheep, privately owned game, dairy cattle, goats, pigs, ostriches, equine, and poultry. The IPCC default values for Africa underestimate emission factors across all livestock categories. The methane emission factors calculated for commercial livestock production systems are more comparable to emission factors from developed countries and the emerging/communal production systems to those of developing countries. This emphasizes the need to develop country-specific emission factors through quantitative research for livestock in all provinces and on all types of production systems to produce accurate baseline figures, which is critical to future mitigation protocols. As part of this study fourteen tropical grass species typical of transitional rangeland regions of South Africa were characterised in terms of chemical composition, in vitro total gas and in vitro methane production. The results of the study demonstrated that in vitro methane production varied between tropical grass species typical of transitional rangeland in South Africa. The variation between species allows for the potential to identify and select species with a lower enteric methane production potential. Panicum maximum, Eragrostis curvula and Elionurus miticus were the three species which produced the lowest in vitro methane production but which also had a crude protein (CP) concentration of more than 3.5% of dry matter (DM) and with an in vitro organic matter digestibility (IVOMD) above the group average for the study. Furthermore, the results of the study revealed that in vitro methane production was higher in Decreaser species compared to Increaser species. Improving the quality of available forages through the use of cultivated pastures and fertilization is known to improve ruminant production efficiency. The effect of level of nitrogen (N) fertilization on certain qualitative parameters and in vitro total gas and methane production of improved grass species commonly utilised in South Africa was evaluated. Treatments included seven grass species divided into two photosynthetic pathways (C3 and C4) with three levels of N fertilization (0, 50 and 100 kg N/ha). No effect was found for N fertilization on in vitro total gas or methane production. The CP concentration increased (P < 0.05) and the NDF concentration tended to decrease (P < 0.1) as the level of N fertilization increased for both C3 and C4 species. Increasing the level of N fertiliser increased (P < 0.05) the methanogenic potential of Dactylis glomorata, Festuca arundinacea and Cenchrus ciliaris after the 24 hour incubation period but no effects (P>0.05) were found after the 48 hour incubation period. Results suggests that the stage of physiological development of forages might have a greater influence on the methanogenic potential of forages compared to the effect of N fertiliser application.
Thesis (PhD)--University of Pretoria, 2017.
Animal and Wildlife Sciences
PhD
Unrestricted

Le méthane (CH4) est un puissant gaz à effet de serre produit lors de la fermentation microbienne anaérobie des aliments dans le rumen. L’un des enjeux majeurs pour le secteur de l’élevage est de trouver des stratégies (alimentaires, génétique) pour réduire les émissions de CH4 tout en maintenant les performances animales. Les techniques de mesure de ces émissions sont coûteuses et difficilement utilisables à grande échelle sur le terrain, d’où la nécessité de trouver des alternatives de mesure ou biomarqueurs pour prédire ces émissions. Les acides gras (AG) du lait ont déjà été identifiés comme indicateurs intéressants de la méthanogenèse chez la vache laitière, mais il convient d’améliorer la précision des équations de prédiction du CH4 existantes ainsi que d'élargir leur domaine d'application à tous types de rations. L'objectif de mon travail de thèse a été de confirmer la pertinence des AG du lait comme indicateurs périphériques de la méthanogénèse chez la vache laitière avec diverses conditions nutritionnelles. Deux bases de données regroupant des données individuelles (issues d’une collaboration scientifique internationale) et moyennes (issues de la littérature) de CH4, de composition en AG du lait et d’autres performances et caractéristiques de l’animal, ainsi que des données de composition chimique des rations, ont été créées. Parallèlement, l’acquisition in vivo de données en conditions expérimentales contrôlées pour des rations mal connues ont permis d’incrémenter la base de données individuelles. Des équations de prédiction des émissions de CH4 [en g/jour, g/kg de matière sèche ingérée (MSI), et g/kg de lait] ont été développées à partir de certains AG du lait, utilisés seuls ou combinés à d’autres variables d’ingestion et de performances laitières, représentant alors des modèles complexes. Des relations entre les émissions de CH4 et la teneur de différents AG du lait (C10:0, iso C17:0 + trans-9 C16:1, iso C16:0, cis-11 C18:1, cis-15 C18:1, cis-9,cis-12 C18:2, et trans-11,cis-15 C18 :2) ont été mises en évidence, confirmant des voies métaboliques communes dans le rumen entre méthanogenèse et métabolisme lipidique. Les équations sont également liées aux types de régimes à partir desquels elles ont été développées. Les équations simples (AG du lait uniquement) sont moins précises que les complexes (erreurs résiduelles de prédiction, respectivement, de 58.6 g/jour, 2.8 g/kg MSI et 3.7 g/kg lait vs. 42.8 g/jour, 2.5 g/kg MSI et 3.3 g/kg lait). Une différence minimum de 16% de CH4 entre stratégies de réduction pourra être mise en évidence par la meilleure équation de prédiction développée. Des équations basées sur des AG bien déterminés par les méthodes infrarouges devront être testées pour évaluer, en routine et à grande échelle, de nouvelles stratégies de réduction des émissions de CH4 entérique chez la vache laitière
Methane (CH4) is a potent greenhouse gas coming from the anaerobic microbial fermentation of the diet in the rumen. One of the main current challenge for the dairy sector is to find CH4 mitigation strategies (diets or genetics) without altering animal performance. Enteric methane measurement methods are costly and very difficult to apply on a large scale on field. Thus, there is a need to develop alternative measurement methods, such as equations based on proxies to predict CH4 emissions. Milk fatty acids (FA) have been identified as potential predictors of the methanogenesis in dairy cattle, but the prediction ability of extant published CH4 equations must be improved, and their domain of applicability must be enlarged to a wide range of diets. The objective of this PhD thesis was to confirm the potential of milk FA as proxies to predict enteric CH4 emissions in dairy cows fed a wide range of diets. Two databases (based on individual and mean data, respectively) were built thanks to an international collaboration, and gathered data on CH4, milk FA composition, dairy performances, diet and animal characteristics. Two in vivo experiments were conducted with the aim to study the effect of dietary strategies poorly documented, on methanogenesis and milk FA. The data from these experiments were included in the created database. Firstly, simple CH4 prediction equations were developed [g/d, g/kg of DMI (DMI), and g/kg of milk] based only on milk FA, and secondly other variables related to cow intake or characteristics, and dairy performance were added and constituted complex equations. Relationships between CH4 and several milk FA (C10:0, iso C17:0 + trans-9 C16:1, iso C16:0, cis-11 C18:1, cis-15 C18:1, cis-9,cis-12 C18:2, and trans-11,cis-15 C18 :2) were found, confirming common rumen metabolic pathways between methanogenesis and lipid metabolism. Equations were also closely related to the diets included in the database used for their development. Simple equations were less accurate than complex ones (prediction error of 58.6 g/d, 2.8 g/kg DMI and 3.7 g/kg milk vs 42.8 g/d, 2.5 g/kg DMI and 3.3 g/kg milk, respectively). A minimum difference of 16% in CH4 emissions between mitigating strategies can be evidenced with the best prediction equation developed in this PhD. Methane prediction equations based on milk FA well determined by infrared spectrometry methods need to be developed in order to be used on a routine basis and on a large scale. These prediction equations would allow studying the effect of novel mitigation strategies of enteric CH4 emissions in dairy cows

Cattle are responsible for greenhouse gas emissions such as carbon dioxide, methane and nitrous oxide. In particular, the cow-calf phase of production accounts for approximately 80 percent of the total beef production system greenhouse gas emissions. Tannins are chemical compounds found in certain forages and they have the potential to help reduce these negative environmental impacts. Thus, given that the cow-calf phase often relies on feeding hay, feeding tannin-containing hays may represent a significant mitigation practice. With my MS program, I sought to explore whether tannin-containing hays fed to mother cows and heifers influence methane and nitrogen emissions relative to feeding traditional legume and grass hays . I found that “non-traditional” hays such as cicer milkvetch and tannin-containing hays such as sainfoin, birdsfoot trefoil and small burnet can help mitigate greenhouse gas and nitrogen emissions produced from heifers and mature cows. Therefore, these hays could be used to feed cattle during the fall and winter to help create a more environmentally friendly cow-calf phase of beef production.

Methane (CH4) emissions and nitrogen (N) excretion in ruminant production systems are major contributors to atmospheric greenhouse gas accumulation and groundwater pollution. This project aimed to evaluate the effects of dietary (fresh grass, grass silage, pelleted grass and concentrates) and animal (breed and sex) factors on CH4 emissions and N utilisation and to develop prediction models for CH4 emissions and N excretion in sheep. During each measurement period, sheep were fed ad libitum once daily in the morning and were housed in individual pens for 14 d before being transferred to individual respiration chambers for 4 d with feed intake, faeces and urine outputs and CH4 emissions measured. Data were analysed using ANOVA to evaluate the effects of diet and animal factors on feed intake, nutrient digestibility, CH4 emissions and N utilisation. Linear and multiple regression equations for CH4 emissions and N excretion were also developed. Feeding pelleted grass, rather than fresh grass or grass silage, reduced CH4 emissions per kg dry matter intake and shifted N excretion from urine to faeces. Feeding concentrate supplementation by 0.5 kg/d with fresh grass had no effect on CH4 emissions per kg feed intake and N retention. Dry matter intake and N intake were the best single predictors for CH4 emissions and N excretion, respectively. However, adding grass nutrient concentrations as supporting factors improved prediction accuracy. Models based on farm level data (animal liveweight and grass chemical composition) showed satisfactory accuracy for use in practice. Increasing feeding level and grass metabolisable energy and water soluble carbohydrate contents, and decreasing grass N content, could optimise the mitigation of both CH4 emissions and N excretion in grazing sheep. The equations provide an approach to quantify CH4 emissions and N excretion and consequently to develop mitigation strategies to reduce the environmental footprint in sheep production systems.

This thesis project explored the use of perennial legumes, including the non-bloating birdsfoot trefoil (BFT; Lotus corniculatus L.) for beef production. In 2011 and 2012, cattle averaged approximately 300 kg at the beginning of the grazing season, and approximately 450 kg in 2013. Average daily gain on pastures ranged from a low of 0.63 kg d-1 on cicer milkvetch (CMV; Astragalus cicer L.) in 2011 and 2013 to a high of 1.03 kg d-1 on Norcen BFT in 2013. Feedlot gains ranged from 1.14 to 1.57 kg d-1. Blood plasma fatty acids did not differ when feeding treatments were imposed, but at the end of each grazing season saturated and omega-6 fatty acids were elevated in feedlot-fed cattle compared with pasture-fed cattle, while trans-vaccenic acid (TVA) and omega-3 fatty acids were elevated in pasture-fed cattle. The ratio of omega-6 to omega-3 fatty acids was always higher in feedlot-fed cattle at the end of the grazing season, but in 2013, when all cattle were nearing slaughter weight, the omega-6 to omega-3 ratio was 50% higher for feedlot-fed than for BFT-fed cattle and double that of grass-fed cattle. Digestive (enteric) methane (CH4) production of beef cows was lower when cattle grazed BFT and CMV pastures (167 and 159 g CH4 per cow per d, respectively) compared to cows on meadow bromegrass (MB; Bromus riparus Rehmann) (355 g CH4 per cow per d). Meadow bromegrass has more fiber than legume forages, which will increase the proportion of acetate to propionate created by microbial digestion in the rumen, increasing the production and release of CH4. Perennial legume forages fix nitrogen, eliminating the need for chemical nitrogen fertilizer, and tannin-containing legumes can be grazed without risk of bloat. These forages will play an important role in developing more environmentally and economically sustainable agricultural production systems.

Problems about greenhouse gas emissions attributed to cattle production and improvements in the productivity of these animals has been growing and becoming increasingly important. Cattle releases methane as part of their digestive process, and this represents loss of energy for the animal. The decomposition of feces releases methane and it can be recovered by digester and transformed into different types of energy. Thus, aiming to quantify the potential production of enteric methane and anaerobic fecal decomposition, as well as to evaluate ruminal and behavioral parameters of cattle fed with cottonseed and vitamin E. Six cannulated cows (864±16 kg) were distributed in a replicate 3x3 Latin square. Treatments were: 1) control diet; 2) CS: basal diet plus 30% cottonseed and 3) CSVitE: basal diet plus 30% of cottonseed plus 500 UI of vitamin E. Results were compared through orthogonal contrast and values were considered significant when P0,05. No differences were observed for dry matter intake (DMI), as well as digestibility of DM and neutral detergent fiber (NDF). Animals supplemented with cottonseed spent more time eating and ruminating and less time in idles. Reduction in the concentration and production of acetate, butyrate and the acetate: propionate ratio was observed in animals fed cottonseed compared to the control. Enteric methane mitigation was observed for the cottonseed treatments compared to the control. Changes in the substrates characteristics used to load the digesters were observed. However, no differences were verified for the total biogas production, methane yield and capacity to recover the energy of the feces in the form of methane. Inclusion of 30% cottonseed can be used as a strategy to mitigate enteric methane, without causing losses in the DMI, nutrients digestibility and anaerobic digestion of feces. In addition, it promoted favorable changes in the ingestive behavior, ruminal fermentation products, as well as in the energy partition of the gastrointestinal tract. Vitamin E when is used as antioxidant had not effect on ruminal fermentation, feeding behavior and feces anaerobic digestion, thus the inclusion is not advised due absence of positive results.
A problemática das emissões de gases de efeito estufa atribuída à produção de bovinos e melhorias na produtividade desses animais vem crescendo e se tornando cada vez mais importante. Bovinos emitem metano como parte do seu processo digestivo, e isto representa perda de energia para o animal. A decomposição das fezes gera metano, este pode ser recuperado por biodigestores e transformado em diferentes tipos de energia. Assim, objetivou-se quantificar o potencial de produção do metano entérico e da decomposição anaeróbia das fezes, bem como avaliar parâmetros ruminais e comportamentais de bovinos alimentados com caroço de algodão e vitamina E. Foram utilizadas seis vacas fistuladas não gestantes e não lactantes (876 kg±16). Os tratamentos foram: 1) Controle: dieta basal; 2) CA: dieta basal mais 30% de caroço de algodão; 3) CAVitE: dieta basal mais 30% de caroço de algodão mais 500 UI vitamina E. O delineamento experimental utilizado foi o quadrado latino. Os resultados foram comparados por contrastes ortogonais e foram considerados significantes valores de P0,05. Não foram verificadas diferenças para o consumo de matéria seca (MS), bem como digestibilidade da MS e da fibra em detergente neutro (FDN). Os animais suplementados com caroço de algodão passaram maior tempo comendo e ruminando e menor tempo em ócio. Houve redução na concentração e produção de acetato, butirato e da relação acetato:propionato dos animais que receberam caroço de algodão comparado ao controle. A inclusão do caroço de algodão provocou mitigação das emissões de metano entérico. Houve alteração nas características dos substratos utilizados para abastecer os biodigestores. No entanto, não foram verificadas diferenças para a produção total de biogás, rendimento de metano e capacidade dos biodigestores em recuperar a energia das fezes na forma de metano. A inclusão de 30% caroço de algodão pode ser utilizada como estratégia para mitigar metano entérico, sem causar perdas no consumo, digestibilidade dos alimentos e na biodigestão anaeróbia das fezes. Além disso, sua inclusão promoveu alterações favoráveis no comportamento ingestivo, nos produtos da fermentação ruminal, bem como na partição de energia do trato gastrointestinal. A vitamina E quando utilizada como antioxidante não possui efeitos sobre a fermentação ruminal, comportamento ingestivo e biodigestão anaeróbia das fezes, assim sua inclusão não é indicada devido a ausência de resultados favoráveis a sua utilização.

Pasture-based systems are important milk suppliers to dairy industry and thereby will play relevant role to support the growing demand for food. However, this additional milk supply must be obtained through higher yields resulting from intensification of existing farming systems through strategies environmentally friendly and economically profitable towards sustainable intensification. The central hypothesis of this study was that simple grazing management strategies can improve the efficiency while reduce the key environmental issues of tropical pasture-based dairy systems. Two experiments were carried out on a rainfed and non-irrigated elephant grass (Pennisetum purpureum Schum. cv. Cameroon) pasture in Piracicaba, SP, Brazil. The objective of the first experiment was to investigate the influence of two pre-grazing targets (95% and maximum canopy light interception during pasture regrowth; LI95% and LIMAX, respectively) on sward structure and herbage nutritive value, dry matter intake (DMI), milk yield, stocking rate, enteric methane (CH4) emissions by Holstein × Jersey dairy cows, and nitrous oxide fluxes from the soil. Results indicated that pre-grazing canopy height was greater for LIMAX (≈135 cm) than LI95% (≈100 cm) and can be used as a reliable field guide for monitoring sward structure. Grazing management based on the LI95% target improved herbage nutritive value and grazing efficiency, allowing greater DMI, milk yield and stocking rate by dairy cows. Daily enteric CH4 emission was not affected; however, cows grazing elephant grass at LI95% were more efficient and emitted 21% less CH4/kg of milk yield and 18% less CH4/kg of DMI. The 51% increase in milk yield per hectare overcame the 29% increase in enteric CH4 emissions per hectare for the LI95% target. Nitrous oxide fluxes were not affected by pre-grazing targets. Overall, strategic grazing management is an environmentally friendly practice that improves the use efficiency of allocated resources through optimization of processes involving plant, ruminant and their interface, and enhances milk production efficiency of tropical pasture-based systems. Once the ideal pre-grazing target was established during he first experiment (LI95%), the second step consisted of a refinement of the first phase. The second objective was to describe and measure the influence of two timings of new paddock allocation to cows (AM and PM) on herbage chemical composition and DMI, milk yield, milk compostion, and enteric CH4 emissions of Holstein × Jersey dairy cows. Results supported the general understanding of diurnal variation in herbage chemical composition towards greater concentrations of dry matter and non-fibrous carbohydrates, and lower concentration of fiber components in the afternoon herbage. However, the higher nutritive value of the afternoon herbage did not result in increasead DMI and milk yield, or decreased intensity of CH4 emission by dairy cows. Our findings also indicate that new paddock allocation in the afternoon can be a simple and useful grazing strategy that results in greater N partitioning to protein yield, and lower excretion of urea N in milk. The association of LI95% pre-grazing target and PM allocation could bring economic, productive and environmental benefits towards sustainable intensification of tropical pasture-based systems.
Sistemas baseados no uso de pastagens são importantes fornecedores de leite para a indústria de latícinios e, dessa forma, terão papel relevante para suportar a crescente demanda por alimentos. No entanto, essa oferta adicional de leite deve ser obtida através de maiores produtividades resultantes da intensificação de sistemas de produção já existentes por meio de estratégias ambientalmente seguras e economicamente rentáveis em direção à intensificação sustentável. A hipótese central deste estudo foi que estratégias simples de manejo do pastejo podem melhorar a eficiência e, ao mesmo tempo, reduzir os principais impactos ambientais dos sistemas de produção animal em pastagens tropicais. Foram realizados dois experimentos em pastagem de capim-elefante (Pennisetum purpureum Schum. Cv. Cameroon) não-irrigada em Piracicaba, SP, Brasil. O objetivo do primeiro experimento foi avaliar a influência de duas metas pré-pastejo (95% e máxima interceptação de luz pelo dossel durante a rebrotação; IL95% e ILMáx, respectivamente) sobre a estrutura do pasto e valor nutritivo da forragem, consumo de matéria seca (CMS), produção de leite, taxa de lotação, emissões de metano entérico (CH4) de vacas HPB × Jersey, e o fluxo de óxido nitroso dos solos. Os resultados indicaram que a altura pré-pastejo foi maior para ILMáx (≈135 cm) do que IL95% (≈100 cm) e pode ser usada como um guia de campo confiável para monitorar a estrutura do pasto. O manejo do pastejo com base nos critérios de IL95% melhorou o valor nutritivo da forragem e a eficiência de pastejo, permitindo maior CMS, produção de leite e taxa de lotação. A emissão diária de CH4 entérico não foi afetada; no entanto, as vacas que pastejaram o capim-elefante manejado por IL95% foram mais eficientes e emitiram 21% menos CH4/kg de leite e 18% menos CH4/kg de MS consumida. O aumento de 51% na produção de leite por hectare superou o aumento de 29% nas emissões de CH4 entérico por hectare para a meta IL95%. Os fluxos de óxido nitroso não foram afetados pelas metas pré-pastejo. De maneira geral, o manejo do pastejo com base na meta IL95% é uma prática ambientalmente segura que melhora a eficiência de uso dos recursos alocados por meio da otimização de processos envolvendo plantas, ruminantes e sua interface, e aumenta a eficiência da produção de leite em sistemas baseados em pastagens tropicais. Uma vez que a meta pré-pastejo ideal foi estabelecida durante o primeiro experimento (IL95%), a segunda etapa consistiu-se em um refinamento da primeira. O segundo objetivo foi descrever e medir a influência de dois horários de alocação de novos piquetes aos animais (AM e PM) sobre a composição química da forragem, CMS, produção e composição do leite, e emissões de CH4 entérico de vacas HPB × Jersey. Os resultados confirmaram a compreensão geral da variação diurna na composição química da forragem em direção a maiores concentrações de matéria seca e de carboidratos não-fibrosos, e menor concentração de componentes da fibra na forragem amostrada pela à tarde. No entanto, o maior valor nutritivo da forragem da tarde não aumentou o CMS e a produção de leite, nem diminuiu a intensidade de emissão de CH4 das vacas leiteiras. Os resultados também indicaram que a alocação à tarde pode ser uma estratégia de manejo simples e útil que resulta em maior partição de N para produção de proteína, e menor excreção de N ureico no leite. A associação da meta pré-pastejo IL95% e a alocação do rebanho para um novo piquete à tarde poderia trazer benefícios econômicos, produtivos e ambientais para a intensificação sustentável de sistemas baseados em pastagens tropicais.

Four desktop studies were conducted to investigate the effects of animal and dietary factors on metabolisable energy (ME) requirement for maintenance (MElli)' efficiency of utilisation of ME for lactation (kl), and enteric methane (CH4) emission rates in lactating dairy cows at the Agri-Food and Biosciences Institute, Hillsborough. The data used in these studies involved nearly 1000 observations of Holstein-Friesian (HF), Norwegian and HF crossbred with Jersey or Norwegian (Fl hybrid) dairy cows, and were collated from 32 respiration calorimeter experiments between 1992 and 2010. Study 1, 3, and 4 evaluated the effect of animal factors and dietary forage proportion on energy metabolism. Study 2 focused on the examination of cow genetic merit influencing the enteric CH4 emission rates. In Study 1, 670 observations of lactating HF dairy cows with various genetic merit indexes were collated. Cow genetic merit in the United Kingdom (UK) is described using two economic indexes, Profit Index (PIN) and Profitable Lifetime Index (PLI). The PIN is based solely on milk production (n = 736, -£30 to +£63), PLI includes milk production and a number of other functional traits including health, fertility and longevity (n = 548, -£131 to +£184). The MEm for individual cows was calculated from heat production (HP) minus energy losses from inefficiencies of ME use for lactation, energy retention and pregnancy, and the kl was obtained from milk energy output (EI) adjusted to zero energy balance (EI(o») divided by ME available for production. Analysis of variance (ANOVA) and linear mixed regression technique were used to examine the effects of cow genetic merit on the MEm and the lq, As there was no significant relationship between cow genetic merit and calculated values of MEm (MJ per kg metabolic body weight, MJ/kgo.7S) or kl using the whole PIN and PLI data set, further analysis was conducted by dividing each dataset of PIN « £3, £3 to £15 and> £15) and PLI « £23, £23 to £67 and> £67) into three sub-groups categorising as low, medium and high genetic groups. Linear relationships between cow genetic merit and energetic parameters were developed to evaluate if there was any significant difference among the coefficients or constants when a common constant or coefficient was used. No significant relationship was found between ME intake (MJ/kgo.7s) and MEm (MJ/kgo.7s), EI(o) (MJ/kgo.7s) or HP (MJ/kgo. 7S) within PIN or PLI sub-groups. These results indicated that cow genetic merit may have no effects on maintenance metabolic rate or energetic efficiency for lactation and high yielding HF cows need more nutrient supply to maximise the production potential. The following study (Study 2) was conducted to investigate the effect of cow genetic merit on the enteric CH4 emissions rates using the same dataset as used in Study 1. The animals had a large range of days in milk (18 to 354), energy corrected milk yields (16.0 to 45.6 kg/d), and CH4 emissions (138 to 598 g/d). The data were analysed using the same programmes as used in Study 1 (AN OVA and regression technique) with the effects of a number of animal and diet factors removed. Within the PIN and PLI datasets there were no significant difference among the three sub-groups in terms of CH4 emission per kg feed intake, energy corrected milk yield, or CH4 energy (CH4-E) output as a proportion of energy intake (P > 0.05). Linear mixed regression using the whole PIN and PLI datasets also demonstrated that there was no significant relationship between either PIN or PLI, and CH4 emission per kg of feed intake or CH4-E output as a proportion of energy intake (P > 0.05). These results indicate that cow genetic merit has little effect on enteric CH4 emissions as a proportion of feed intake. Enteric CH4 production may mainly relate to total feed intake and dietary nutrient composition. effects of a number of animal and diet factors removed. Within the PIN and PLI datasets there were no significant difference among the three sub-groups in terms of CH4 emission per kg feed intake, energy corrected milk yield, or CH4 energy (CH4-E) output as a proportion of energy intake (P > 0.05). Linear mixed regression using the whole PIN and PLI datasets also demonstrated that there was no significant relationship between either PIN or PLI, and CH4 emission per kg of feed intake or CH4-E output as a proportion of energy intake (P > 0.05). These results indicate that cow genetic merit has little effect on enteric CH4 emissions as a proportion of feed intake. Enteric CH4 production may mainly relate to total feed intake and dietary nutrient composition.

Objetivou-se avaliar o uso de nitrato de cálcio (NC) na alimentação de ruminantes com vistas à mitigação da emissão de metano. Foram utilizadas quatro fêmeas de cada subespécie, Bos taurus taurus (Holandês) e vBos taurus indicus (Nelore), com peso médio inicial de 909,0 kg ± 72,0 e 387,0 kg ± 25,5, respectivamente, alimentadas com diferentes níveis de nitrato de cálcio na dieta (0%, 1%, 2% e 3%), sendo utilizado delineamento quadrado latino 4X4 replicado. O experimento teve duração de 4 períodos de 28 dias cada. Foram avaliados, a ingestão, excreção e digestibilidade de nutrientes, por meio de marcador externo dióxido de titânio, o comportamento ingestivo, com monitoramento visual por 24 horas, parâmetros sanguíneos, dinâmica ruminal, com esvaziamento total do rumen, contagem de protozoários, fermentação ruminal, pela técnica ex-situ, parâmetros urinários e balanço de nitrogênio, com coleta manual de urina tipo spot, e a biodigestão dos dejetos, por biodigestores do tipo batelada. Os taurinos apresentaram valores superiores para CMS, ingestão e digestibilidade de nutrientes e excreção de MS, PB, FDN, FDA, N, MO e EB, e inferiores para CMS em relação ao PV e PM. Os zebuínos apresentaram maiores taxas de ingestão, ruminação e mastigação de MS e FDN em min/kg, tendo valores inferiores para as mesmas taxas em kg/min. A genética e a dose de nitrato influenciaram as variáveis séricas, porém sem valores fora da normalidade. Quanto à dinâmica ruminal, os taurinos apresentaram valores absolutos superiores, e valores em relação ao PV e PM inferiores. Os zebuínos apresentaram maiores pH médio e mínimo e menos tempo de pH abaixo de 6,2, e maior contagem de protozoários. As concentrações de N-NH3, volume e produção de CH4 foram maiores para os zebuínos. Os taurinos apresentaram valores mais elevados para N microbiano (g/dia) e balanço de N retido (g/kg N ingerido), e menores valores para balanço de N nas fezes (g/kgN ingerido) e N microbiano (mg/kgPM.d-1). O aumento no nível de NC na dieta aumentou a digestibilidade de EE e ENN, tempo médio ruminando e taxa de mastigação de MS e FDN (min/kg), e diminuiu o CMS em relação ao PV e PM e excreção de MS, EE, ENN, MO e EB. A taxa de ingestão de MS e FDN (kg/min), a concentração de creatinina na urina (mg/kgPV), o tempo total comendo e balanço de nitrogênio amoniacal o rúmen sofreram efeito quadrático com a adição de NC na dieta. A porcentagem de FDN, PB e EE nos afluentes dos bidigestores sofreram influência da dose de nitrato na alimentação das vacas. Os biodigestores contendo os dejetos de taurinos tiveram os afluentes com maiores valores de FDN e FDA e menor teor de sólidos totais (ST), com menor volume de biogás e CH4 e menor relação de CH4/quantidade de fezes. Os taurinos apresentaram melhor aproveitamento do alimento, produzindo menos CH4, com menor rendimento verdadeiro de produção de metano nos biodigestores. A adição de NC afetou o consumo, digestibilidade e utilização do nitrogênio porém, sem afetar a produção de CH4 nem a eficiencia dos biodigestores.
The aim of the present study was evaluate the use of calcium nitrate in the feeding of ruminants to mitigate of methane. Four females cattle from each subspecies of cattle, Bos taurus taurus (Holstein) and Bos taurus indicus (Nellore), with initial average weight of 909,0 kg ± 72,0 e 387,0 kg ± 25,5, respectively, were used, and they were fed with distinct levels of calcium nitrate in the diet (0%, 1%, 2% e 3%) at four periods of 28 days each. Experimental design was composed by a replicated Latin square 4X4. Were avaluated: ingestion, excretion and digestibility of nutrients, by means of external marker titanium dioxide; the observation of behavior parameters during 24 hours; serum analysis; rumen content collection, aiming assessment of fermentation; protozoa count; ruminal fermentation by the ex-situ technique; manual urine collection for measurement of urinary compounds and nitrogen balance; and the anaerobic digestion of feces using batch digesters. Holsteins presented higher values for the DMI, ingestion and digestibility of the nutrients and excretion of DM, CP, NDF, ADF, N, OM e GE, and lower values for DMI at body weight (BW) and metabolic weight (MW) basis. Nellore cattle showed higher rates of ingestion, rumination and chewing of DM e NDF min/kg, having lower values for the same rates in kg/min. Serum variables were influenced by genetics and nitrate levels, but without values beyond normality. As rumen dynamics, Holsteins presented superior absolute values and inferior values when these parameters were calculated in BW and MW basis. The zebu cattle presented medium and minimum pH larger and less time pH below 6.2, having larger count for protozoa count. Nellore had higher concentrations for NH3, CH4 and production of CH4. Holstein presented higher values for microbial N (g/day) and N retained balance (g/kg N ingested) and lower values for N balance in feces (g/kgN ingested) and microbial N (mg/kgMW.d-1). The increase in the level of CN in the diet increased linearly the digestibility of EE and NNE, average time ruminating, chewing rate for DM and NDF (min/kg), and decreased the DMI in BW and MW basis and the excretion of DM, EE, NNE, OM and GE. The intake rate of DM and NDF kg/min, creatinine in urine (mg/kgBW), the total time eating and NH3 balance showed quadratic effect by increasing the addition of CN in the diet. The levels of nitrate on animal feed influenced the percentage of NDF, CP and EE in the batch digesters afluents. The biodigestors containing the taurine feces presented the highest values of NDF/ ADF affluent and lowest values for total solids (TS), lower volume of biogas and CH4 and lower ratio of CH4/amount of feces. Taurines presented better use of the feed, producing lesser CH4, and lower ultimate methane yield at batch digesters. The CN levels affected the intake, digestibility and nitrogen metabolism, however without affecting the production of CH4 or the batch digester efficiency.

Beef cattle production is highly criticized because of the high use of land and water resources, and by the pollution (e.g., the gas methane in a cow’s breath and nitrogen in urine) produced by cows fed in feedlots. In contrast to feedlots diets and grasses, some plants (e.g., legumes) contain bioactive compounds (condensed tannins) that reduce pollution and enhance animal nutrition. In my research, I observed that cows grazing a tannin-containing legume (birdsfoot trefoil; BFT) had methane emissions similar to cows fed a feedlot ration with comparable weight gains. Cows in the BFT treatment gained more weight than cows grazing grass (meadow brome) or a legume without tannins (cicer milkvetch). Additionally, I estimated the potential areas in the state of Utah than can sustain birdsfoot trefoil production, with 412,250 ha distributed mostly in the Box elder, Cache, Millard and Sanpete counties. Thus, feeding tannin-containing legumes to cows is a viable alternative to feedlot rations, with greater levels of productivity than other pasture-based systems, which can lead to a more sustainable production of beef.

Reindeer (Rangifer tarandus tarandus) are large Holarctic herbivores whose heterogeneous diet has led to the development of a unique gastrointestinal microbiota, essential for the digestion of arctic flora, which may include a large proportion of lichens during winter. Lichens are rich in plant secondary metabolites, which may affect members of the gut microbial consortium, such as the methane-producing methanogenic archaea. Little is known about the effect of lichen consumption on the rumen and cecum microbiotas and how this may affect methanogenesis in reindeer. Here, we examined the effects of dietary lichens on the reindeer gut microbiota, especially methanogens. Samples from the rumen and cecum were collected from two groups of reindeer, fed either lichens (Ld: n = 4), or a standard pelleted feed (Pd: n = 3). Microbial densities (methanogens, bacteria and protozoa) were quantified using quantitative real-time PCR and methanogen and bacterial diversities were determined by 454 pyrosequencing of the 16S rRNA genes. In general, the density of methanogens were not significantly affected (p>0.05) by the intake of lichens. Methanobrevibacter constituted the main archaeal genus (>95% of reads), with Mbr. thaueri CW as the dominant species in both groups of reindeer. Bacteria belonging to the uncharacterized Ruminococcaceae and the genus Prevotella were the dominant phylotypes in the rumen and cecum, in both diets (ranging between 16-38% total sequences). Bacteria belonging to the genus Ruminococcus (3.5% to 0.6%; p = 0.001) and uncharacterized phylotypes within the order Bacteroidales (8.4% to 1.3%; p = 0.027), were significantly decreased in the rumen of lichen-fed reindeer, but not in the cecum (p = 0.2 and p = 0.087, respectively). UniFrac-based analyses showed archaeal and bacterial libraries were significantly different between diets, in both the cecum and the rumen (vegan::Adonis: pseudo-F<0.05). Based upon previous literature, we suggest that the altered methanogen and bacterial profiles may account for expected lower methane emissions from lichen-fed reindeer.

En zone tropicale, la production de lait et de viande par les ruminants est limitée par une faible disponibilité et une qualité médiocre des fourrages. A ces contraintes alimentaires s’ajoute l’impact environnemental lié en particulier aux émissions de méthane entérique par les ruminants. L’objectif de cette thèse était de comparer la production de méthane en milieu tempéré et en milieu tropical, puis de valoriser des fourrages tropicaux connus pour leur richesse en tanins dont les propriétés anti-méthanogènes sont reconnues, et qui peuvent réduire l’impact environnemental sans compromettre la productivité animale. Cette thèse comporte trois expérimentations distinctes. La première consistait en une étude in vivo visant à déterminer si les différences de digestibilité, de production de méthane, de fermentation et d’écosystème microbien du rumen observées entre les zones tempérées et tropicales proviennent de l’environnement (site d’expérimentation en milieu tempéré ou tropical), du fourrage (produit en zone tempérée ou tropicale), ou du génotype ovin (race de zone tempérée ou tropicale). Les résultats ont montré que les différences sont liées en priorité à la nature du fourrage, et sont influencées par les interactions entre génotype, caractéristiques du fourrage et environnement. La seconde expérience consistait à étudier l’effet de plantes riches en tanins condensés (feuilles de Gliricidia sepium, Leucaena leucocephala, Manihot esculenta) sur la production de méthane, l’ingestion et la digestibilité de la ration, les fermentations et l’écosystème microbien du rumen. Un essai in vivo a montré que l’incorporation de ces plantes à raison de 40% du régime d’ovins sous forme de granulés permettait de réduire le méthane entérique sans effets indésirables sur la digestibilité et la fermentation ruminale. Un essai in vitro a montré que le principal facteur de la réponse a été la dose de tanins condensés plutôt que la source. La troisième expérience consistait en l’étude in situ et in vitro du pouvoir anti-méthanogène et de la dégradation dans le rumen de plantes riches en tanins hydrolysables (feuilles et gousses d’Acacia nilotica) ou en tanins condensés (feuilles de Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala, Manihot esculenta, Musa spp). Les résultats obtenus suggèrent que les tanins hydrolysables conviennent mieux à la réduction des émissions de méthane que les tanins condensés car ils inhibent fortement la production de méthane sans effets négatifs marqués sur la fermentation ruminale. Les effets des tanins sur la production de méthane et la fermentation dans le rumen ont été en partie expliqués par le devenir des différentes fractions des tanins (libres, associés aux protéines ou aux fibres) dans le rumen. L’association de plantes riches en tanins hydrolysables et en tanins condensés ne parvient pas à dégager de possibles synergies entre ces de types de molécules. Ce travail a permis de montrer qu’il était possible de réduire les émissions de méthane entérique par les ruminants en milieu tropical par la consommation de fourrages riches en tanins hydrolysables sans compromettre les processus digestifs dans le rumen ; la diminution de la méthanogenèse avec les tanins condensés présente plus de risque de réduire les fermentations
In tropical areas, dairy and meat production from ruminants is limited by low availability and poor quality of forages. In addition to this dietary constraint, the emission of enteric methane under these less productive conditions is proportionally larger than under temperate conditions. The aim of this work is i) to compare enteric methane production in tropical and temperate environments, and ii) to promote tropical forages rich in hydrolysable or condensed tannins having anti-methanogenic properties that could reduce the environmental impact without compromising animal productivity. This work includes three separate studies. The first one was an in vivo study aiming to determine the origin of the differences of digestibility, methane production, ruminal fermentation and microbial ecosystem between tropical and temperate countries using as variables: the site of the experiment (tropics or temperate area), the type of forage (grown in the tropics or in temperate areas); and the animal genotype (tropical or temperate). Results showed that differences are mainly due to forages, but with interactions between nature of forages, environment and genotype. The objective of the second study was to determine the effect of plants rich in condensed tannins (leaves of Gliricidia sepium, Leucaena leucocephala, and Manihot esculenta) on methane production, intake, digestibility, ruminal fermentation and microbial ecosystem. An in vivo trial demonstrated that the inclusion of 40% of these plants as pellets in sheep diet reduced enteric methane without compromising the nutritive value of the diet. An in vitro trial showed that the response to tannins was more due to tannin concentration than to the plant species. In the third study, plants rich in hydrolysable tannins (leaves and pods of Acacia nilotica) or in condensed tannins (leaves of Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala, Manihot esculenta, Musa spp) were studied for their anti-methanogenic properties and their ruminal degradation in an in situ and an in vitro trial. Results suggest that hydrolysable tannins are more suitable than condensed tannins for mitigating methane emission because of a strong reduction in methane production without negatively affecting ruminal fermentation. These results have been partly explained by the fate of the different fractions of condensed tannins (free, protein-bound and fibre-bound) in the rumen. The association of plants rich in hydrolysable tannins with plants rich in condensed tannins failed to produce synergistic effects on methane mitigation. This work showed that enteric methane production by ruminants could be reduced in tropical areas by the inclusion of hydrolysable tannins without compromising digestive processes in the rumen; methane mitigation with condensed tannins may result in a reduction of the extent of fermentation

The nutritional value of browse foliage from shrub and tree species in the Kalahari region of the Northern Cape, South Africa is not well quantified and analysed. In this study, nineteen browse (shrub and tree) species were selected and their foliage harvested during April 2012, when the plants are at mid vegetative stage of growth in order to determine its chemical composition, nutritional values and its potential to reduce methane production. The foliage materials were analysed for crude protein (CP), ash content, dry matter (DM), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), total phenols and condensed tannins. The in vitro gas production technique was used to determine the volume of gas and methane (CH4) produced. IIn vitro organic matter digestibility (IVOMD), volatile fatty acids (VFA) and rumen ammonia (NH3-N) concentration were also determined. In the gas production study the forage samples were studied either in the absence or presence of polyethylene glycol 8000 (PEG) to determine the effects of tannin on various parameters of interest. Crude protein ranged from 70-320 g/kg DM, ash 40-210 g/kg DM, NDF 350-508 g/kg DM, ADF 270-530 g/kg DM, ADL 85-320 g/kg DM and neural detergent fibre nitrogen (NDFN) 47-93 g/kg DM. Total tannins ranged from 9-320 g/kg DM, condensed tannins 2-125 g/kg DM and hydrolysable tannins which ranged from 3-195 g/kg DM. The CP concentration of all 19 browse species included in the current study, except Olea europaea, Terminalia sericea and Monechma genistifoluim will meet the maintenance requirements of ruminants based on CP concentrations as indicated in the NRC (2007) guidelines. Among the shrubs and trees, Acacia luederitzii and Monechma incanum showed the best potential to decrease methane production by up to 90 % after 48 h of incubation. The secondary compounds (mainly tannins) of the browse species had no significant (p<0.001) effect on IVOMD and rumen ammonia concentration but the VFA, methane and gas production was decreased significantly (p<0.001). In the last experiment, an in vitro gas production experiment was conducted to evaluate the potential of 6 selected browse species (with high, medium and low condensed tannin concentrations) when supplemented to Eragrostis trichopophora. This was done in order to determine their potential as anti-methanogenic additives in the diet of ruminant animals. These browse species were supplemented with Eragrostis trichopophora at a ratio of 30:70. The effects of addition of these browse as a supplement, on rumen fermentation and methane production were studied. Of the six browse included in the current study, A. luederitzii and M. incanum decreased methane production by more than 50 %, but digestibility and VFA production was decreased. From these 3 studies, it seems that Boscia albitrunca and Rhus lancea has the best potential to be used as a feed supplement during times of drought, depending on the availability of these browse foliage, while A. luederitzii and M. incanum seems to have the best potential to consistently decrease methane production, but at the expense of digestibility. An in vivo feeding trail inside a methane chamber should be considered in the future in order to complement this study to determine the nutrient availability and degradability of these browse species and to estimate the actual potential reduction in enteric methane production.
Dissertation (MScAgric)--University of Pretoria, 2015.
tm2015
Animal and Wildlife Sciences
MScAgric
Unrestricted

Residual Feed Intake (RFI) and enteric methane (CH4) emissions were measured over two years on 120 Angus bulls receiving either a silage-hay diet or a silage-grain diet (277±28 and 286±25 d of age in year 1; 249±23 and 250±23 d of age in year 2). Emissions were similar between diets (240 vs. 248  7.9 L d-1, P>0.05; silage-hay vs. silage-grain) and RFI grouping (P>0.05). DMI increased for high RFI bulls versus low RFI bulls (7.68±0.2 and 8.24±0.2 kg DM d-1, low vs. high). Correlations between RFIfat and CH4 emissions were not significant. These findings agree with previous studies and suggest that RFI ranking may be associated with metabolic mechanisms other than fermentation efficiency.
October 2016

Methane emissions of 60 steers (321 ± 14 kg) fed isocaloric forage diets differing in crude protein (CP) content were measured at ambient daily temperatures averaging -17.5°C to determine if increased nitrogen status, measured by blood urea nitrogen (BUN), decrease CH4 as a percent of gross energy intake (% GEI) from backgrounding cattle. Average BUN concentrations (mmol L-1) were 0.81, 1.82, 3.05 and 3.51 (SE ± 0.108) for diets with 6.9% (low), 10.3% (adequate for rumen microbes), 11.1% (adequate for muscle growth) and 13.6% (excessive) CP respectively. Methane (% GEI) emissions decreased with increasing CP over time (P=0.04). Increasing CP content increased BUN levels and decreased methane emissions (% GEI). Although models were developed to predict CH4 emissions (% GEI) from steers and cows using a backward-elimination process, BUN accounted for only 0.7 to 5.7% of the partial R2 and therefore has limited value when modelling methane emission predictions.
February 2016

This study was conducted to determine if nutrient utilization and enteric methane (CH4) emissions could be improved in overwintering beef cows consuming low-quality forage supplemented with protein in the form of dried distillers grain with solubles (DDGS) in thermal-neutral and cold-stressed environments. Thirty mature, dry and non-pregnant beef cows were divided into three treatment groups and fed diets consisting of low-quality (6.0% crude protein; CP) forage with no DDGS (control, CON), 10% DDGS (borderline sufficient CP, 8.7% CP), or 20% DDGS (excess CP, 11.6% CP). Cold acclimatization did not appear to affect nutrient intake and digestibility by beef cows, but increased N and P excretion by 1.2x and 2.5x, respectively. Cold acclimatized cows reduced energy excretion by 26.8% (7.1 vs. 5.2 ± 0.30% GEI in fall and winter, respectively; P < 0.0001) in accordance with a 33.8% increase in rumen fluid rate of passage (ROP). Supplementation with DDGS improved digestibility of N and P (40.6 vs. 61.2 ± 2.45% N and -23.9 vs. 5.7 ± 5.95% P for CON and 20%DDGS, respectively; P < 0.0001) by increasing digestible substrate in the diet. Protein supplementation increased rumen NH3-N concentrations (1.5, 2.1 and 3.1 ± 0.15 mg 100 mL-1; P < 0.0001) enough to increase rumen fermentation efficiency, resulting in 18.5% lower enteric CH4 emissions when CP was fed in excess of animal requirements. Total excretion of N and P were increased two- and 45-fold, respectively, when excess CP was fed. Reduced enteric CH4 emissions as a result of cold acclimatization suggest an advantage for the Canadian beef herd in terms of environmental sustainability. Supplementing CP in excess of cow requirements may improve nutrient utilization and rumen fermentation efficiency, and mitigate enteric CH4 emissions in beef cows fed low-quality forage diets, but may also contribute to greater N and P loading of soil and ground water.