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Hickson, R. E., R. L. Laven, N. Lopez-Villalobos, P. R. Kenyon i S. T. Morris. "Postpartum anoestrous interval in first-lactation beef and dairy-beef crossbred cows". Animal Production Science 52, nr 7 (2012): 478. http://dx.doi.org/10.1071/an11288.
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In New Zealand, beef-breeding cows are required to wean a calf every year, and the weight of calf at weaning is a major driver of the efficiency of the breeding cow. Weaning weight can be increased by increasing milk yield of the cow such as by incorporating dairy breed genetics into the breeding cows, and by having early born calves which are, therefore, older at weaning. This experiment examined postpartum anoestrous interval and pregnancy rate to rebreeding in 109 beef-breed and beef-cross-dairy breed first-lactation cows suckling their own calves. Cows with a Jersey component had a shorter postpartum anoestrous interval than cows without (90 versus 97–101 days; P < 0.05). Pregnancy rates after 42 days of joining with bulls were 83–97% for straight-bred Angus, Angus-cross-Friesian, Angus-cross-Jersey and Angus-cross-Kiwicross (Friesian-cross-Jersey) cows, but only 41% for straight-bred Friesian cows (P < 0.05). For every day younger heifers reached puberty, postpartum anoestrous interval was reduced by 0.07 ± 0.02 days (P < 0.01) indicating that age at puberty could be used as a predictor of subsequent fertility. The Jersey-component cows offered advantages in fertility traits and may be worthwhile incorporating into beef-breeding cow herds.
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McGregor, B. A., i J. F. Graham. "Fibre production by beef cows". Animal Production Science 50, nr 6 (2010): 568. http://dx.doi.org/10.1071/an09219.
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Cattle grow and shed fibre which assists them adapt to seasonal changes in the environment. In the absence of cattle fibre production data for southern Australia, Angus, Hereford, Simmental and Limousin cows and crosses between these breeds grazing perennial pastures at Hamilton, Victoria were sampled in late winter. The fibre-growing area on the sides of cattle was measured, fibre sampled at the mid-side site and the sampling area determined. Fibre was tested for fibre diameter distribution, clean washing yield and fibre length measured. Cows were 3–7 years of age, liveweights were 412–712 kg and the mean fibre-growing area was 2.2 m2. This produced an average 682 g of total fibre (range 346–1175 g). The mean fibre diameter of all fibres was 51.7 µm (range 43–62 µm) and 18% of fibres were <36 µm (range 6–39%). The clean washing yield was 92.4% (range 87.4–95.8%). Fibre length averaged 21 mm. Increasing the age, liveweight and condition score of cows and increasing weight of clean fibre were associated with significant increases in mean fibre diameter. Breed of cattle did not affect fibre production (P > 0.1) but did affect mean fibre diameter (P < 0.05). The quantity of fibre production indicates potential for low value textile production. The high level of total fibre production, twice that of an earlier report, and fibre shedding from cattle suggests that white fibre-producing animals such as Merino sheep, Angora and cashmere goats and alpaca should avoid using cattle-handling facilities, particularly in the month before shearing.
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Morter, Raymond L., Charles H. Armstrong, Harold E. Amstutz i H. Leon Thacker. "Systemic Salmonellosis in Mature Beef Cows". Journal of Veterinary Diagnostic Investigation 1, nr 1 (styczeń 1989): 22–24. http://dx.doi.org/10.1177/104063878900100108.
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Systemic infection of mature beef cows with Salmonella typhimurium resulted in death of cows, abortions, and premature births. Salmonella typhimurium was isolated from the kidney, liver, and spleen of cows but not from an aborted fetus. Diarrhea was not a prominent clinical feature of the epizootic. The source of the salmonella was not determined.
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Santos, N. R., G. C. Lamb, D. R. Brown i R. O. Gilbert. "Postpartum endometrial cytology in beef cows". Theriogenology 71, nr 5 (marzec 2009): 739–45. http://dx.doi.org/10.1016/j.theriogenology.2008.09.043.
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Mathis, Clay P., i Jason E. Sawyer. "Nutritional Management of Grazing Beef Cows". Veterinary Clinics of North America: Food Animal Practice 23, nr 1 (marzec 2007): 1–19. http://dx.doi.org/10.1016/j.cvfa.2006.12.001.
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Lira, Stephen M., Jon T. Biermacher, Evan Whitley i Devlon Ford. "185 Strategies for managing open beef cows". Journal of Animal Science 97, Supplement_1 (lipiec 2019): 63. http://dx.doi.org/10.1093/jas/skz053.142.
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Abstract Open beef cows account for between 15 and 30% of a spring-calving cow/calf operation’s annual revenue; however, most producers commonly sell open cows at weaning when prices are at a seasonal low. A three-year (2015–2018) study was conducted using open beef cows (n = 244) from a spring-calving herd in south-central Oklahoma. The objective of the study was to determine whether or not the net return of retaining, feeding, rebreeding, and marketing rebred cows was greater than the revenue from selling open cows at weaning. Each year at weaning, open cows were sorted into Thin or Moderate groups using an average threeman Body Condition Score (BCS). Thin cows (BCS < 5.5) received a ration of 11.4% CP and 63.9% TDN, while Moderate cows (5.5 ≤ BCS ≤ 6.0) received 10.4% CP and 55.2% TDN. Rations were formulated to transform the final condition of all cattle to a BCS of 6. Two rested bulls were assigned to each feeding group during the first 60 days of retention. After 90 days of retention all cattle were pregnancy tested via ultrasound. Enterprise budgeting techniques were used to calculate revenue, costs, and net return for each cow. Mixed effects (ANOVA) models using the Mixed Procedure in SAS were used to determine the fixed effects of feeding treatment, age, pregnancy status, and market type on ending weight and BCS and net return. Year and individual animal were tested and treated as random for each model analyzed. On average, net return was affected by feeding treatment (P = 0.0323), age (P < 0.0001), and pregnancy status (P < 0.0001). The results suggest that producers who have the ability to sort and feed young, thin cows in poorer condition and rebreed them using rested bulls can expect to earn $68/head more than selling them as open at weaning
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Bailey, C. R., A. L. Goetsch, D. S. Hubbell i C. F. Rosenkrans, Jr. "Effects of monensin on beef cow reproduction". Canadian Journal of Animal Science 88, nr 1 (1.03.2008): 113–15. http://dx.doi.org/10.4141/cjas07082.
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This study was designed to evaluate the effects of monensin with or without grain supplementation on reproduction of beef cows consuming bermudagrass hay. Monensin supplemented at 200 mg head-1 d-1, with or without grain supplementation, shortened the period from calving to conception and increased calving percentage in beef cows consuming bermudagrass hay. Key words: Monensin, beef cows, reproduction
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Khakimov, Ismagil, Rinat Mudarisov i Aleksandr Akimov. "BEEF COWS BODY CONDITION SCORING AND ITS MEASUREMENTS RELATIONSHIP". Bulletin Samara State Agricultural Academy 5, nr 2 (8.05.2020): 40–46. http://dx.doi.org/10.12737/37338.
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The purpose of the study is improving the efficiency of breeding work in selection of cows by live weight, body measurements with mandatory consideration of animal condition score. The degree and nature of relationship be-tween live weight and body measurements of beef cows with condition score, regression coefficient were calculat-ed. The research was carried out on beef Hereford and Kazakh white-headed cows. A high positive relationship between live weight, body measurements and the condition score of cows was established. The regression coeffi-cient showed that change in finish by 1 point increases the live weight of Hereford cows of the first group by 46.3 kg, the second – by 44.2 kg, and the third – by 42.1 kg. The cows of the second group have the largest bulk, they signif-icantly exceeded the Hereford and Kazakh white-headed cows of the first and third groups by this indicator. The difference was 51.2 and 45.9 kg, respectively, the coefficients of variability – varied between 4.1 to 9.2%. Hereford Cows of the second group were superior in heart girth (with a difference of 4 cm) to cows of the first group and 10.6 cm to cows of the third group. The coefficients of variability ranged within 12.9 to 27.0 %. In terms to heart girth (by 1.05 and 0.95 cm) and chest depth (by 8.9 and 2.9 cm), the cows of the second group were superior to the cows of the first and the third groups, respectively (the difference is not reliable). The variation coefficients ranged within 10.3 to 15.7% for heart girth and from 13.0 to 16.7% for chest depth.
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Blasi, D. A., J. K. Ward, T. J. Klopfenstein i R. A. Britton. "Escape protein for beef cows: III. Performance of lactating beef cows grazing smooth brome or big bluestem." Journal of Animal Science 69, nr 6 (1991): 2294. http://dx.doi.org/10.2527/1991.6962294x.
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Vaz, Ricardo Zambarda, José Fernando Piva Lobato, João Restle, Pablo Tavares Costa, Otoniel Geter Lauz Ferreira, Javier alexander Bethacourt Garcia, Lidiane Raquel Eloy i João Luiz Benavides Costa. "Effect of live weight of beef cows on calf production efficiency". Research, Society and Development 9, nr 9 (2.09.2020): e679007632. http://dx.doi.org/10.33448/rsd-v9i9.7632.
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The objective was to evaluate the development and reproductive performance of beef cows of different body weights at calving were evaluated. Milk yield and calf production efficiency were assessed in secundiparous Braford cows classified at calving according to weight as Light (325.2±3.7 kg), Moderate (347.7±4.0 kg), and Heavy (384.2±4.1 kg). Heavy cows had higher total milk yield than Light cows, but did not differ from Moderate, reflecting in calves weighing at weaning 82.1, 76.6, and 76.9 kg, respectively. Differences on pregnancy rates for Light (90.0%, 18 pregnant cows/2 of eligible cows), Moderate (70.2%, 12 pregnant cows/5 of eligible cows), and Heavy (62.5%, 10 pregnant cows/6 of eligible cows) were not detected. Light cows were more productive and efficient when production performance was adjusted for the pregnancy rates than Moderate and Heavy cows. Production of kilograms of calves adjusted for pregnancy was 20.5, 16.2±0.5, and 14.0±0.5 kg for the Light, Moderate, and Heavy cows, respectively. Heavy and Moderate cows were less efficient as compared with the Light ones for production of calves adjusted for their calving interval. Light cows produce more kilograms of calf/cow, requiring the same amount of milk to produce one kilogram of calf. Light cows also have higher efficiency converting milk into calf weight than Moderate and Heavy cows. The productivity and efficiency of breeding herds should be evaluated by the combination of pregnancy rate and kilograms of weaned calves per cow exposed to breeding.
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Carluccio, Augusto, Ippolito De Amicis, Monica Probo, Brunella Giangaspero i Maria Cristina Veronesi. "Prevalence, survival and subsequent fertility of dairy and beef cows with uterine prolapse". Acta Veterinaria Hungarica 68, nr 1 (marzec 2020): 91–94. http://dx.doi.org/10.1556/004.2020.00017.
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AbstractThe aim of this study was to evaluate the prevalence of uterine prolapse in cows and assess its effects on survival and subsequent fertility. Of 33,450 calving cows considered retrospectively, 216 (0.6%) developed uterine prolapse. A higher prevalence was found in beef cows (n = 57/5,700 cows, 1%) compared to dairy cows (n = 157/27,750 cows, 0.6%). Treatment consisted of cleaning and replacing the uterus with local administration of antibiotics, and applying a harness for uterine containment. The recovery rate was 81.9% (n = 177), similar in dairy (n = 129; 81.1%) and beef (n = 48; 84.2%) cows. Of the 216 cows with uterine prolapse, 18 (8.3%) died before or immediately after treatment; 21 cows (9.7%) were voluntarily culled for economic reasons (low milk yield, low fertility, insufficient weight gain). All recovered dairy cows were artificially inseminated with semen of proven fertility after a voluntary waiting period of 50 days; the beef cows were naturally mated. Among the 172 inseminated/mated cows, 84.7% (n = 150) became pregnant (83.7% dairy cows, 87.5% beef cows), while 15.2% (n = 27) did not conceive. Recurrence of uterine prolapse at subsequent calvings was recorded in one dairy cow. Based upon the data presented here, treated cows with uterine prolapse showed high chances of survival and conception, and a low risk of recurrence.
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Hayanti, Sari Yanti, Amrozi Amrozi, Aryogi Aryogi i Mokhamad Fakhrul Ulum. "Postpartum perineal muscle sonogram in Madura beef cow". Veterinary World 14, nr 2 (9.02.2021): 380–92. http://dx.doi.org/10.14202/vetworld.2021.380-392.
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Background and Aim: Ultrasonography (USG) is useful for non-invasively identifying changes that occur in soft tissue architecture. The objective of this research was to demonstrate postpartum (PP) uterine involution through the changes of perineal muscle intensity and thickness in Madura beef cow by ultrasonography. Materials and Methods: Madura's breed cows used in the research consist of eight non-pregnant (NP) cows and three PP cow. The transrectal and transperineal USG imaging of NP cows was performed on days 1, 33, and 65. USG imaging of PP cows was performed every day starting from day 1 (24 h after parturition) until day 21 PP. Transrectal USG of the reproductive tract was performed for the cervix, corpus uteri, and cornua uteri. USG was performed transcutaneously over the perineal area for coccygeus and levator ani muscles at the longitudinal and transverse angles. Reproductive tract diameter and perineal muscle intensity and thickness were measured with ultrasound imaging. Results: The analysis of the sonogram of PP cows showed that the diameter of the cervix, corpus uteri, and cornua uteri decreased within 21 days PP. The transverse view of the coccygeus muscle of PP cows showed decreased muscle intensity and thickness. On the other hand, the longitudinal view showed increased coccygeus muscle intensity and thickness. The transverse view of the coccygeus muscle of NP cows showed increased muscle intensity, while muscle thickness was reduced. Sonogram analysis of the levator ani muscle of PP cows showed decreased muscle intensity with increasing muscle thickness. However, imaging of the levator ani muscle of NP cows showed a decrease in both intensity and muscle thickness. There was a significant difference in the mean value intensity of the scanning view analysis results of the levator ani muscle of the PP cow (523.6 AU increased to 672.1 AU) and the NP cow (515.9 AU decreased to 465.4 AU). Furthermore, there was a significant difference (p<0.05) in the mean value thickness of both scanning view analyses of the coccygeus and levator ani muscles of PP cows (5.8 mm increased to 6.5 mm and 3.8 mm increased to 4.8 mm, respectively) and NP cows (8.8 mm increased to 9.1 mm and 5.9 mm decreased to 4.9 mm, respectively). Conclusion: We found that the perineal muscles, namely, the levator ani muscle and coccygeus muscle, change in size, and intensity during uterine involution as demonstrated on Madura beef cow.
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Farias, Gustavo Duarte, Liliane Cerdótes, Ricardo Zambarda Vaz, João Restle, Marcia Ferreira Bitencourt, Dari Celestino Alves Filho i Ivan Luiz Brondani. "Biological efficiency of Charolais beef cows of different body sizes". Semina: Ciências Agrárias 39, nr 4 (2.08.2018): 1737. http://dx.doi.org/10.5433/1679-0359.2018v39n4p1737.
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This study aimed to evaluate the production, reproductive performance, and productive efficiency of predominantly Charolais cows and their calves (Straightbred, ¾ C, ¼ N) according to body size at calving. Sixty-three cow-calf pairs were used and classified into three weight groups: Light (331.3±5.8 kg), Moderate (385.9±5.3 kg), and Heavy (424.4±6.2 kg). The classes were formed using half standard deviations above or below the average weight of the cows at calving. For each pair, the body weight was evaluated at calving, at weaning (63 days), at the beginning and at end of the reproductive period, and at 9 months for the calves. Pregnancy rates were similar (P > 0.05) between weight groups. The calves did not differ (P > 0.05) in terms of body weight and weight gain from calving until pregnancy diagnosis (210 days). The heavy cows had greater weight variations from 210 days to 270 days than the light cows. The calf production rate (kg calf/cow kept in herds) did not differ between weight groups. However, in relation to the weight of the cows at 210 days, light cows were 11.28% and 13.02% more productive (P < 0.05), than moderate and heavy cows, respectively. Light cows were more efficient than the other classes of cows at calving and at 210 days old. Our simulations showed that there were more kilograms for sale in herds of light cows (53.085 kg) than moderate and heavy cows (52.310 and 52.870 kg, respectively), while maintaining the structures of the herd constant. The size of the Charolais cow did not influence the weight of calves from calving until 7 months of age or their reproductive performance provided they were weaned early. The need for space for the maintenance of the cow-calf pair increased as the weight of the cows increased. In herds with smaller cows, higher numbers and a higher production of weight for sale are observed than in herds with moderate and heavy cows. Light cows were the most efficient at calving and during pregnancy diagnosis at 210 days.
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Pochukalin, A. Ye, Yu M. Reznikova, S. V. Priyma i O. V. Rizun. "BREEDING ACHIEVEMENT OF BEEF CATTLE-BREEDING OF UKRAINE: ZNAMENSK INTRABREED TYPE OF POLESSIAN BEEF BREED". Animal Breeding and Genetics 52 (1.11.2016): 94–108. http://dx.doi.org/10.31073/abg.52.12.
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The aim of our research was to conduct a retrospective analysis and to study the current state of the subjects breeding Znamensk intrabreed type of Polessian Beef breed and to assess main economically useful traits and genealogical structure.
Material and methods. Research of productive and economic activity of breeding farms has been carried out based on the electronic database of State Register of Breeding Subjects in Livestock for 2003-2016. Analysis of the number of breeding animals, distribution of cows by age, animals’ live weight, milk (as a calf’s live weight at the age of 7 months) and reproductive abilities has been performed based on breeding account (form №7-myas) for 2010, 2012, 2014, 2016.
Results of research. The most breeding farms meet the minimum requirements of the target standard of Znamensk intrabreed type on the main quantitative traits of animal productivity. "Kolos" АLLC, Kirovograd region and «Agrikor Holding" LLC, Chernihiv region were the most numerous. High realization of genetic potential of meat productivity (daily gain of live weight above 1000 g) was observed at animals in «Kolos» АLLC and «Sharivske» PE. There have been sold 222 head of the breeding youngsters for 13 years.
The greatest number of animals was observed according to annual reports in 2012. It can be explained by the number of subjects conducting the selection and breeding work with the intrabreed type. The share of cows did not exceed 43.0% (2012), bull – 1.5% (2010), calves of different gender and age groups – 66.1% (2014). 85.5% of all the available breeding stock (5369 head) was approved and 67.8% corresponded to elite and elite-record classes.
Live weight of the approved cows has increased by 7.5% at the age of 3 years, 9.7% at the age of 4 years and 11.1% at the age of 5 years since 2010. Differential for live weight of cows at the age of 4 and 5 years was 9 and 11 kg on the average.
There was adequate number of animals, live weight of which was in a wide range, that is from 551 kg and above. So, such cows were 111 head in 2010 and 234 head in 2016. These cows realise genetic makings of high productivity sufficiently and they are material for selecting the best representatives of Znamensk intrabreed type.
Gradual increase of milk ability was noted from 2010 till 2016 after the first calving by 13.7%, the second – 12.2, the third – 11.7, and by 11.9% on average. Differential for milk ability of cows was 5 kg (2010, 2012), 11 kg (2014) and 2 kg (2016) on average.
Average calving interval of cows for the period are oscillatory in nature and didn’t exceed 420 days during 2010-2014. Gradual increase of age at first calving of heifers by 101 days was observed from 2010 to 2014 with reduction to 824 days for next two years. It should be noted violation of course of cows’ and heifers’ calvings, it was 29 and 36 cases in 2010 and 2012 respectively, whereas in subsequent periods, these values were significantly lower or non-existent. It may indicate a high level of veterinary services and compliance of technologies of feeding and management.
Efficiency of beef cattle-breeding depends on the growing of calves. Analysis of the results shows that live weight of calves at the age of 210 days has increased in each investigational year. The values are oscillatory in nature between 8 and 15 months. Sexual dimorphism was confirmed and proven – bull-calves had higher growth rate compared to heifers.
Significant reduction in the livestock number of the approved bloodlines and their absence in some cases (Radyst 113 and Darovanyi 400) was observed. This is due to the increased share of Polessian Beef and Charolais bulls used for reproduction. There were 139 cows, 27 heifers and 13 calves in group belonging to Polessian Beef and Charolais bloodlines in 2012, whereas in 2014, 281, 193 and 18 respectively, representing 81% of the total population.
Conclusions. The research revealed that livestock of the type were concentrated in «Agrikor Holding» breeding farm, Pryluky district, Chernihiv region with a total of 922 head, including 348 cows. Productivity of animals by the valuation results at the beginning of 2016 (live weight, milk ability, reproduction) significantly increased. Current genealogical structure of Znamensk intrabreed type was represented by bulls belonging to Polessian Beef and Charolais bloodlines, share of which was 81%.
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Vara, Carina Crizel da, Magali Floriano da Silveira, Ricardo Zambarda Vaz, João Restle, Diego Soares Machado i Stefani Macari. "Body size in beef cows and its influence on calf production". Semina: Ciências Agrárias 41, nr 6supl2 (6.11.2020): 3299–310. http://dx.doi.org/10.5433/1679-0359.2020v41n6supl2p3299.
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Cattle farming becomes more intensive when the productive efficiency of the cows is increased, and nutrition is adjusted to the animal biotype. Eighty purebred Charolais and Nellore cows and their crosses between 3 and 7 years of age, were grouped for body weight at calving into Light (332.6 kg), Moderate (385.3 kg) and Heavy (444.6 kg). Cows and their calves were weighed at calving, at 63 days (early weaning) and at 210 days. The estimated milk production of the cows was evaluated by manual milking at 21, 42 and 63 days postpartum. The difference in the weight of the cows at calving was maintained during lactation and at 210 days postpartum. The body size of the cow did not influence milk production. Heavier cows produce heavier calves up to 365 days of age compared to lighter cows. The reproductive performance of the cows is not affected by their weight. The production of kilograms of calf for every 100 kilograms of cow at calving and weaning is higher in Light cows. The production of kilograms of calf adjusted for the pregnancy rate of the cows is higher in Heavy cows. Production efficiency in kilograms of calf per area is lower in Heavy cows.
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Buddenberg, B. J., C. J. Brown, Z. B. Johnson i R. S. Honea. "Maternal Behavior of Beef Cows at Parturition". Journal of Animal Science 62, nr 1 (1.01.1986): 42–46. http://dx.doi.org/10.2527/jas1986.62142x.
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Russel, A. J. F., I. A. Wright i E. A. Hunter. "Factors Affecting Reproductive Efficiency in Beef Cows". Proceedings of the British Society of Animal Production (1972) 1989 (marzec 1989): 136. http://dx.doi.org/10.1017/s0308229600011260.
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Successful and timely rebreeding is of major importance to the economics of suckler cow enterprises. Research into the causes of reprodutive failure and extended calving intervals can be difficult, not least because of the need for experiments involving large numbers of animals if statistically significant treatment effects are to be demonstrated. Useful information however, can be obtained from the analysis of data derived from a number of relatively small-scale experiments, not necessarily on reproduction per se, but in which records of reproductive performance are available.This paper deals with the analysis of data on the reproductive performance of beef cows used in a number of experiments on the effects of nutrition during pregnancy and lactation on components of production such as milk yield and composition, calf birth weight and early calf growth rate. The objective of the analysis was to identify the major factors affecting calving interval and to quantify the magnitude of the effects of these factors.
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Diskin, M. G., i D. A. Kenny. "Managing the reproductive performance of beef cows". Theriogenology 86, nr 1 (lipiec 2016): 379–87. http://dx.doi.org/10.1016/j.theriogenology.2016.04.052.
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Hoyt, Phillip G., Marjorie S. Gill, Kenneth L. Angel, Stephen D. Gaunt, Sharon M. Dial i Ricky M. Landreneau. "Corticosteroid-responsive thrombocytopenia in two beef cows". Journal of the American Veterinary Medical Association 217, nr 5 (wrzesień 2000): 717–20. http://dx.doi.org/10.2460/javma.2000.217.717.
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Dorn, C. G., J. F. Baker, R. Knutson i D. C. Kraemer. "Embryo recovery from early postpartum beef cows". Theriogenology 31, nr 1 (styczeń 1989): 184. http://dx.doi.org/10.1016/0093-691x(89)90592-x.
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Roche, J. F., M. A. Crowe i M. P. Boland. "Postpartum anoestrus in dairy and beef cows". Animal Reproduction Science 28, nr 1-4 (lipiec 1992): 371–78. http://dx.doi.org/10.1016/0378-4320(92)90123-u.
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Hetzel, D. J. S., M. J. Mackinnon, R. Dixon i K. W. Entwistle. "Fertility in a tropical beef herd divergently selected for pregnancy rate". Animal Science 49, nr 1 (sierpień 1989): 73–81. http://dx.doi.org/10.1017/s0003356100004268.
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ABSTRACTSelection on the basis of estimated breeding value for cow fertility was successful in establishing two distinct lines of high (H) and low (L) fertility in a herd of Droughtmaster (Brahman × Shorthorn) cattle. The average difference in pregnancy rates over 3 years between the H and L line was 12% (P < 0·01) in the selected cows. In lactating cows this difference was 17% indicating that lactational anoestrus was an important component of the line difference in fertility. The total calf losses between confirmed pregnancy and weaning were 17%, but there were no line differences. Cow mortalities were 5% higher (P < 0·01) in pregnant cows than in empty cows but were similar in the H and L 'lines.H cows were proportionately 0·06 lighter in body weight (P < 0·01) at mating and 0·075 lighter (P < 0·01) at weaning than L cows. Much of this difference was due to the greater number of calves carried and weaned by H cows during their lifetime. Smaller lactation effects on weight gains and weight losses in H cows indicated that these cows were less sensitive in terms of weight gain to seasonal fluctuations in nutrition. H cows conceived earlier than L cows in 2 out of the 3 years and reared calves which were proportionately 0·04 lighter at weaning (P < 0·01). It is suggested that lower milk production in H cows leading to shorter periods of lactational anoestrous, combined with lower sensitivity to nutritional stress, was responsible for their higher fertility.
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Higdon, H. L., P. G. Parnell, J. E. Hill i J. C. Spitzer. "Streptozocin-induced Pancreatic Islet Destruction in Beef Cows". Veterinary Pathology 38, nr 6 (listopad 2001): 715–20. http://dx.doi.org/10.1354/vp.38-6-715.
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Streptozocin (STZ) induces diabetes mellitus in sheep and pigs. To test the effect of STZ in cattle, cows were given 75–150 mg STZ per kilogram of body weight. Cows receiving 150 mg/kg required euthanasia within 24 hours after infusion because of the severe systemic effects of STZ. Seven cows receiving doses of ≤100 mg/kg had mild to marked decrease in islet immunoreactivity for insulin and in pancreatic islet density and mild to severe tubulointerstitial nephritis. Two cows receiving 75 and 85 mg/kg STZ regained their ability to produce insulin and return blood glucose to basal levels. One cow given 100 mg/kg STZ developed insulin insufficiency consistent with type I diabetes mellitus. These findings demonstrate the susceptibility of the bovine pancreas to STZ; however, severe systemic complications were encountered. Alternative dosages and methodologies should be considered in future attempts to induce diabetes in cattle using STZ.
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Finger, A., K. P. Patison, B. M. Heath i D. L. Swain. "Changes in the group associations of free-ranging beef cows at calving". Animal Production Science 54, nr 3 (2014): 270. http://dx.doi.org/10.1071/an12423.
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Dyadic association between individuals forms the basis of group structures for herding animals. Group associations and social bonds are dynamic and can result in the establishment of new subgroups. The onset of parturition and the introduction of an offspring create a social change for a mother that is part of a herd. There is a need to nurture the young, develop and maintain a strong maternal bond, and build or maintain social networks within the larger herd. The present study explored associations within a herd of cattle that included pregnant cows and cows with calves (maternal cows). Group dynamics were determined by daily observations of group associations over an 11-week period. During the period, some pregnant cows calved and it was possible to quantify their associations before and post-calving. The associations between individual cows were quantified using a half-weight index (HWI). The HWI data for the maternal and pregnant class of cows were compared. The overall HWI data and the individual class data (pregnant or maternal) were tested against a random model, using data that were generated using permutation methods. There were significant differences in the associations of the pregnant and maternal cows; the maternal cows had stronger associations with other maternal cows while the pregnant cows showed evidence of weaker associations with other pregnant cows and the maternal cows. As pregnant cows calved, they developed stronger associations with other maternal cows. The present study provided evidence that pregnant cows prefer to maintain a degree of isolation, but strengthen their social bonds with other mothers as they enter a maternal phase.
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Worthington, Mary Clarke, Grace C. Ott, Matthew H. Poore i Carrie L. Pickworth. "57 Impact of weaning strategy on beef cow performance". Journal of Animal Science 97, Supplement_1 (lipiec 2019): 1. http://dx.doi.org/10.1093/jas/skz053.000.
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Abstract It has been shown that physiologic stress in beef cattle can impact animal performance. Weaning stress is recognized as a major stress in a calf’s life. However, less is known of its impacts on the dam or developing fetus, as the dam is at the end of the second trimester at weaning. Therefore, the objective was to investigate the impact of weaning stress on cow performance. A total of 240 cows from two locations were assigned to one of three weaning strategies: abrupt removal of the calf on d 0 (n = 80), d 7 cow-calf fenceline contact (n = 81), and late weaning on d 84 (n = 79). Cows averaged 16 and 24 weeks of gestation on d 0 and d 84 respectively. Weights and BCS were obtained monthly. Behavioral observations occurred over the week before and after weaning for each weaning period. Five late-wean cows per location were milked on d 14 and d 70 to estimate milk yield throughout the late wean period. Data were analyzed using the MIXED procedure of SAS with BW and BCS utilizing repeated measures. Means are declared different at P ≤ 0.05. The ADG over the course of the study was lower (P < 0.05) for the late weaned cows compared to the abrupt weaned cows. This was also reflected by change in body condition where late weaned cows dropped from a 5.7 to a 4.9 (P < 0.05) over the 105 d. Milk production in late weaned cows decreased over time (6.0 and 4.4 kg/d for d 14 and 70, respectively; P = 0.05). Energy expenditure for lactation may have contributed to the drop in BCS of the late weaned compared with the non-lactating cows and could compromise third trimester growth of calf in utero. The results of this study warrant further exploration of the effect of weaning stress on dams and their developing fetuses.
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Worthington, Mary Clarke, Grace C. Ott, Matthew H. Poore i Carrie L. Pickworth. "48 Impact of weaning strategy on beef cow performance". Journal of Animal Science 97, Supplement_1 (lipiec 2019): 83. http://dx.doi.org/10.1093/jas/skz053.190.
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Abstract It has been shown that physiologic stress in beef cattle can impact animal performance. Weaning stress is recognized as a major stress in a calf’s life. However, less is known of its impacts on the dam or developing fetus, as the dam is at the end of the second trimester at weaning. Therefore, the objective was to investigate the impact of weaning stress on cow performance. A total of 240 cows from two locations were assigned to one of three weaning strategies: abrupt removal of the calf on d 0 (n = 80), d 7 cow-calf fenceline contact (n = 81), and late weaning on d 84 (n = 79). Cows averaged 16 and 24 weeks of gestation on d 0 and d 84 respectively. Weights and BCS were obtained monthly. Behavioral observations occurred over the week before and after weaning for each weaning period. Five late-wean cows per location were milked on d 14 and d 70 to estimate milk yield throughout the late wean period. Data were analyzed using the MIXED procedure of SAS with BW and BCS utilizing repeated measures. Means are declared different at P ≤ 0.05. The ADG over the course of the study was lower (P < 0.05) for the late weaned cows compared to the abrupt weaned cows. This was also reflected by change in body condition where late weaned cows dropped from a 5.7 to a 4.9 (P < 0.05) over the 105 d. Milk production in late weaned cows decreased over time (6.0 and 4.4 kg/d for d 14 and 70, respectively; P = 0.05). Energy expenditure for lactation may have contributed to the drop in BCS of the late weaned compared with the non-lactating cows and could compromise third trimester growth of calf in utero. The results of this study warrant further exploration of the effect of weaning stress on dams and their developing fetuses.
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McCaughey, W. P., K. Wittenberg i D. Corrigan. "Impact of pasture type on methane production by lactating beef cows". Canadian Journal of Animal Science 79, nr 2 (1.06.1999): 221–26. http://dx.doi.org/10.4141/a98-107.
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In order to determine the quantity of methane (CH4) produced by lactating beef cows on pasture, 16 Hereford–Simmental first-calf heifers with a mean weight of 511.2 ± 5.8 kg were randomly selected from a larger group of cows (n = 60) on a grazing management experiment and used to evaluate the effects of pasture type on ruminal CH4 production using the sulfur hexafluoride (SF6) tracer-gas technique. Pasture treatments consisted of two pasture types, alfalfa-grass [78% alfalfa (Medicago sativa L.) – 22% meadow bromegrass (Bromus biebersteinii Roem and Schult.)] or 100% meadow bromegrass at each of two fertility levels (either unfertilized or soil test recommended fertilizer levels) with two replications of each pasture treatment (8 pastures). Cows were managed using a "put and take" stocking system to leave equal residual herbage mass on all treatments following the grazing period in each paddock. During the 69-d grazing season, two cows from each pasture were sampled to determine daily forage intake and CH4 production on four occasions. The chemical composition of diets differed between pasture types and sampling periods. Dry matter intake was greater for cows grazing alfalfa–grass pastures than for cows grazing grass-only pastures (11.4 vs. 9.7 kg DM d−1. P < 0.018). However, methane production was greater for cows grazing alfalfa–grass pastures than for cows grazing grass-only pastures (373.8 vs. 411.0 L CH4 d−1. P < 0.008). Consequently, energy lost through eructation of CH4 was less for cows grazing alfalfa–grass pastures than it was for cows grazing grass-only pastures (7.1 vs. 9.5% of GEI; P < 0.001). Key words: Methane, cattle, environment, digestion efficiency, pasture, forage
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Wright, I. A., J. R. Jones, T. J. Maxwell, A. J. F. Russel i E. A. Hunter. "The effect of genotype × environment interactions on biological efficiency in beef cows". Animal Production 58, nr 2 (kwiecień 1994): 197–207. http://dx.doi.org/10.1017/s1357729800042508.
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AbstractAn experiment was conducted to examine the response of three genotypes of beef cows to contrasting levels of nutrition supplied from grazed pasture. Twenty-two Hereford × Friesian (HF), 20 Aberdeen Angus × Friesian (AF) and 24 Welsh Black (WB) spring-calving beef cows with their Charolais-cross calves were used in 4 years consecutively. During the summer grazing period they grazed permanent pasture maintained at either 4 to 5 cm (short) or 7 to 8 cm (tall) sward surface height. Sward height treatment significantly (P < 0·001) affected cow and calf live-weight gain (0·498 v. 0·041 (s.e.d. 0·0405) kg/day and 1·12 v. 0·90 (s.e.d. 0·021) kg/day for cow and calf live-weight gain on the tall and short swards respectively). The live-weight gains of the HF and WB cows were similar, but the AF cows gained less weight on the tall sward and lost weight on the short sward. Calf live-weight gain reflected cow milk yield, with the calves from HF and AF cows having similar live weight gains (1·06 and 1·02 kg/day respectively) and those from WB cows having lower gains (0·95 kg/day; P < 0·001). The effect of sward height on calf live-weight gain was greatest in the WB-born calves because of the lower milk yield from WB cows. Body chemical composition changes of cows were predicted from live weight and body condition score, using prediction equations derived from separate groups of cows which were slaughtered at a range of body compositions for determination of chemical composition. Energy balances, calculated from changes in chemical composition, showed the AF cows to have the lowest energy balances with the WB cows the highest. Calculation of energetic efficiency and land use efficiency of weaned calf production taking account of annual food requirements indicated that the HF cows were most efficient, and the WB cows least efficient. The effect of increasing nutritional environment (as represented by sward height treatment) was such as to increase energetic efficiency for all genotypes, but land use efficiency was increased for HF and AF cows, and decreased for WB cows. These results indicate the factors such as size of cows, milk yield potential and pattern of nutrient partitioning can influence energetic land use efficiency of weaned calf production, and that important interactions between genotype and nutritional environment can occur in different measures of efficiency.
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DEGEN, A. A., i B. A. YOUNG. "THE PERFORMANCE OF PREGNANT BEEF COWS RELYING ON SNOW AS A WATER SOURCE". Canadian Journal of Animal Science 70, nr 2 (1.06.1990): 507–15. http://dx.doi.org/10.4141/cjas90-062.
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Body mass change, water influx, metabolic heat production and rectal temperature were measured in four pregnant beef cows offered only snow as a water source (snow cows) and in four pregnant beef cows that also had access to heated water (water cows). The study was carried out during winter (December to March) in Alberta, Canada. There was no difference between treatment groups in any of these measurements indicating that the snow cows were obtaining adequate water to satisfy their requirements and that no added nutrient energy was required to melt the snow and bring the water to body temperature. Milk yield in the two groups, measured in early spring when water was available to all cows, was similar as was the growth rate of the calves. Milk yield averaged 8.2 kg d−1 during weeks 2–4 of lactation and 4.6 kg d−1 during weeks 14–16. Average daily gain from birth to weaning (6 mo) of calves suckling the snow cows was 0.74 kg and of calves suckling the water cows was 0.70 kg. It was concluded that there was no detrimental effect of withholding liquid water from pregnant beef cows when snow is available and that cows can use snow as their only water source for lengthy periods of time during winter. Key words: Pregnant cows, snow, water, water influx, metabolic heat production
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Hand, R. K., L. A. Goonewardene, B. J. Yaremcio i R. Westra. "A study on the prevalence of cracked claws among beef cows". Canadian Journal of Animal Science 72, nr 1 (1.03.1992): 165–68. http://dx.doi.org/10.4141/cjas92-019.
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A survey of the prevalence of vertical (sand) cracks on claws of cows on pasture in northwest Alberta found 261 out of 1183 or 22.7% cows affected. Among cows with cracks, 62% had a single crack while 29% had two cracks. There were significantly (P = 0.00001) more cracks on the outside (80.6%) compared with the inside (19.4%) claw. Significantly (P = 0.0002) more of the severe cracks were found on the outside claw. Key words: Claw, cracks, cows, severity, prevalence
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Borges, Luiz Felipe Kruel, Rogério Ferreira, Lucas Carvalho Siqueira, Rodrigo Camponogara Bohrer, Jacson William Borstmann, João Francisco Coelho de Oliveira i Paulo Bayard Dias Gonçalves. "Artificial insemination system without estrous observation in suckled beef cows". Ciência Rural 39, nr 2 (14.11.2008): 496–501. http://dx.doi.org/10.1590/s0103-84782008005000075.
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The aim was to develop a timed artificial insemination (TAI) system in suckled beef cows. Cows (n=227), 60-80 days postpartum, received estradiol benzoate (5mg) and a vaginal device containing 250µg of medroxyprogesterone acetate (MPA; day 0). On day six, cloprostenol (125µg) and eCG (400IU) were administrated and calves were weaned for 88h. The devices were removed on day seven (BioRep group) or on day eight (TAI group). All cows of TAI group and cows of BioRep group that did not exhibit standing estrus received GnRH (100µg) on day 9. In experiment I, the follicular growth was monitored daily by transrectal ultrasound exams, from day 6 to day 9. The average size of the dominant follicle on day nine was 11.1±0.99mm (BioRep, n=7) and 11.5±0.65mm (TAI, n=7) and all animals ovulated. In experiment II, the BioRep group cows (n=106) were observed for estrous behavior after withdrawal of the device, twice a day for 48h, and inseminated 12h after detection. In the TAI group (n=107), the devices were withdrawn on day eight and after 24h these cows and those from the BioRep group, which were not stand in estrus, received 100µg of GnRH and TAI 16h later. The pregnancy rates were 57.6% (BioRep) and 52.3% (TAI). In conclusion, an increase on MPA exposure time did not affect the follicular dynamics and pregnancy rates and allow TAI without estrous observation. Furthermore, the treatment for eight days provides an efficient TAI system in suckled beef cows.
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Fan, L. Q., J. W. Wilton i P. E. Colucci. "Genetic parameters for feed intake and efficiency in lactating beef cows". Canadian Journal of Animal Science 76, nr 1 (1.03.1996): 81–87. http://dx.doi.org/10.4141/cjas96-011.
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Genetic parameters of feed intake and efficiency and production traits for lactating beef cows were estimated from data collected from 1980 to 1988 at the Elora Beef Research Centre, Guelph, Ontario. Estimates were obtained using restricted maximum likelihood (REML) with an individual animal model with year–season–treatment, sex of calf, parity, breeding system, covariate daily change of backfat depth and direct genetic and permanent environmental effects. The data included 1174 observations, 511 cows, 369 dam–maternal grand dam pairs and 245 sires of cows. Feed efficiency for milk was calculated as milk yield relative to energy consumed for milk and maintenance and residual feed consumption as estimated energy intake minus energy requirements as estimated by the National Research Council. Heritabilities for Herefords alone and total data, respectively, were estimated to be 0.02 and 0.11 for cow's daily ME intake (MEI), 0.26 and 0.26 for daily milk yield (DMY), 0.45 and 0.33 for milk fat percentage (MFP), 0.29 and 0.40 for metabolic body weight (MBW), 0.21 and 0.10 for calf weaning weight as a proportion of cow weight at weaning (PPW), 0.18 and 0.11 for feed efficiency for milk (FE), and 0.23 and 0.03 for residual feed consumption (RFC). Genetic correlations of output (DMY) and input (MEI) were 0.31 for Hereford and 0.75 for the total data. Genetic correlations of RFC with both output (DMY) and input (MEI) were low. Genetically, PPW was positively associated with FE and DMY and negatively associated with MBW. Key words: Genetic parameters, feed efficiency, lactation, beef cow
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Farrell, Lydia J., Stephen T. Morris, Paul R. Kenyon i Peter R. Tozer. "Simulating Beef Cattle Herd Productivity with Varying Cow Liveweight and Fixed Feed Supply". Agriculture 11, nr 1 (6.01.2021): 35. http://dx.doi.org/10.3390/agriculture11010035.
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The liveweight of New Zealand beef cows has increased in recent decades due to selection for higher growth rates. Published data suggest that the efficiency of beef cow production decreases with increasing cow liveweight. Changes in beef herd size, feed demand, production, and cash operating surplus (COS) were simulated with average mature cow liveweight varied to 450, 500, 550, and 600 kg. With total annual beef feed demand fixed at the same level, in all scenarios cow numbers and numbers of weaned calves decreased with increasing cow liveweight. When the model was run with consistent efficiency of calf production across the mature cow liveweights (scenario A), heavier cows were more profitable. However, using published efficiency data (scenarios B and C), herds of heavier cows were less profitable. The likely most realistic scenario for New Zealand hill country farms (scenario B) had COS decrease from New Zealand Dollars (NZD) 456/ha with a herd of 450 kg cows to NZD 424/ha with 600 kg cows. Reductions in COS were relatively small, which may not deter farmers from breeding heavier cows for higher calf growth rates. However, the results of this analysis combined with indirect potential economic impacts suggest that the heaviest cows may not be optimal for New Zealand hill country conditions.
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WILTON, J. W., J. McWHIR, G. K. MACLEOD i G. J. KING. "GENOTYPE-NUTRITION INTERACTION FOR REPRODUCTION OF BEEF COWS". Canadian Journal of Animal Science 67, nr 3 (1.09.1987): 789–95. http://dx.doi.org/10.4141/cjas87-081.
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Two levels of feed during early lactation (70 and 100% of NRC requirements) were used for five groups of genotypes (Herefords, small beef breed crosses, large beef breed crosses, small beef by dairy crosses and large beef by dairy crosses). Days to first ovulation (DFO), days to pregnancy (DP) and pregnancy rates were measured over 2 yr. No interaction of feed level by breed group was found for any measure of reproductive performance, milk yield or weaning weight of calf. The lower level of feeding significantly decreased DFO (by 6 d) and DP (by 5 d). Dairy crosses had similar DFO to Hereford, but less than beef crosses. When milk yield and weight were used as covariates, replacing breed group classifications, DFO was found not to be significantly influenced by 6-wk measurements of milk (P = 0.11) nor weight (P = 0.89). Number of days to pregnancy was similarly unaffected by milk yield (P = 0.19), although it was increased by increased weight of cow (P = 0.03). Significant (P < 0.05) differences among breed groups remained after adjustment for weight and milk for DP but not for DFO. More variation was accounted for in DFO (R2 = 0.48) than DP (R2 = 0.20). Repeatability of performance from one year to the next was higher for DFO (0.26 ± 0.13) than for DP (0.00 ± 0.15). Key words: Genotype-nutrition interaction, beef cows, reproduction
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NKUUHE, J. R., i J. G. MANNS. "RELATIONSHIP BETWEEN TIME OF PROSTAGLANDIN INJECTION AND OVULATION IN BEEF CATTLE". Canadian Journal of Animal Science 65, nr 2 (1.06.1985): 405–9. http://dx.doi.org/10.4141/cjas85-047.
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Experiments were conducted to determine whether the time of day when a luteolytic dose of PGF is given affects the time of onset of estrus and ovulation in cattle. Two similar experiments were conducted with a total of 14 cows and 10 heifers. Animals were divided into two equal groups, A and B, and 25 mg of PGF was injected at either 0600 or 1800 h. Overall, the times from PGF injection to the onset of estrus, LH peak or ovulation were not affected (P > 0.05) by the time of day (0600 vs. 1800 h) PGF was given. However, when data on heifers and cows were analyzed separately, the LH peak appeared earlier in heifers than cows (62.2 ± 3.3 vs. 71.0 ± 1.9 h, P < 0.05), heifers ovulated earlier than cows (83.9 ± 3.9 vs. 99.2 ± 2.4 h, P < 0.01) and the interval between the LH peak and ovulation was shorter in heifers than cows (21.5 ± 2.2 vs. 28.3 ± 2.1 h, P < 0.05). Key words: Prostaglandin, ovulation, LH surge, cows
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FREDEEN, H. T., G. M. WEISS, G. W. RAHNEFELD, DOUG WARD, J. E. LAWSON i J. A. NEWMAN. "BEEF CATTLE REPRODUCTION IN RELATION TO THE ENVIRONMENT". Canadian Journal of Animal Science 68, nr 1 (1.03.1988): 15–28. http://dx.doi.org/10.4141/cjas88-002.
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Results are reported from a 10-yr study of lifetime reproductive performance of beef cows maintained under two contrasting environments. The data comprised records for 8160 cow years. The breeding herds were maintained for 6 yr in accordance with the management practices conventional to each location with winter management changed (to drylot feeding) for the final 4 yr. Location differences in cow performance favored the herd maintained under semi-intensive management (Brandon, Manitoba). Conception rates were higher, calf mortality lower, and calf gains preweaning greater than recorded for the contemporary herd maintained under extensive range management (Manyberries, Alberta). These differences in performance gave Brandon a 16% advantage in weight of calf weaned per mating exposure. Cows at Manyberries, in the fall of 1977, the seventh year of study, were lighter (15%) and had less fat (60%) than their Brandon contemporaries. These differences increased to 19 and 80% during the first winter in feedlot confinement even though the daily feed energy allowance was 20% above requirements (National Research Council-National Academy of Sciences, NRC-NAS). Conception rates at Manyberries were seriously affected by mortality, both cows and calves, inversely related to cow fat at calving. An increase in feed inputs at Manyberries (42% above NRC-NAS) the following winter, coupled with the opportunity for tissue restoration provided by a barren year, reversed the downward trends in weight and fat and weight equivalence of the two herds was achieved by 1980. Milk yields from pastured cows during the last 4 yr were generally higher for the Brandon herd, but calf growth rate from birth to 2 mo of age was greater at Manyberries. Key words: Beef cows, reproductive performance, lifespan, environment
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Weik, Franziska, Rebecca E. Hickson, Stephen T. Morris, Dorian J. Garrick i Jason A. Archer. "Genetic Parameters for Maternal Performance Traits in Commercially Farmed New Zealand Beef Cattle". Animals 11, nr 9 (26.08.2021): 2509. http://dx.doi.org/10.3390/ani11092509.
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Maternal performance is a major driver of profitability in cow-calf beef cattle enterprises. The aim of this research was to evaluate the inheritance of maternal performance traits and examine the intercorrelation among reproduction, live weight, hip height, body condition and maternal contribution to calf weaning weight in 15-month-old heifers, 2-year-old cows and mature cows in New Zealand beef herds. Data were collected on a total of 14,241 cows and their progeny on five commercial New Zealand hill country farms. Heritabilities were low for reproductive traits in heifers and mature cows (0–0.06) but were greater in 2-year-old cows (0.12–0.21). Body condition scores were lowly (0.15–0.26) and live weights (0.42–0.48) and hip heights (0.47–0.65) highly heritable in heifers, 2-year-old cows and mature cows. Results indicate that 2-year-old cows with higher genetic potential for rebreeding ability may have greater genetic merit for live weight, hip height and body condition as heifers (rg = 0.19–0.54) but are unlikely to be larger cows at maturity (rg = −0.27–−0.10). The maternal genetic effect on weaning weight had a heritability of 0.20 and was negatively genetically correlated with body condition score in lactating cows (rg = −0.55–−0.40) but positively genetically correlated with rebreeding performance (rg = 0.48).
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NAASZ, C. D., i H. L. MILLER. "EFFECTS OF BULL EXPOSURE ON POSTPARTUM INTERVAL AND REPRODUCTIVE PERFORMANCE IN BEEF COWS". Canadian Journal of Animal Science 70, nr 2 (1.06.1990): 537–42. http://dx.doi.org/10.4141/cjas90-065.
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One hundred and thirteen spring calving beef cows were utilized to study the effect of bull exposure during the early postpartum period on return to estrus and fertility. In the spring of 1985 and 1986, cows were randomly exposed to epididymectomized bulls (BE) 3–7 d after calving until beginning of the breeding season (n = 37, 1985; n = 20, 1986) or not exposed to bulls (NE) (n = 35, 1985; n = 21, 1986). Cows were observed for estrus twice daily beginning approximately 4 wk after the start of calving until synchronization. Estrous cycles of all cows were synchronized with Syncro-Mate B® (SMB) and cows inseminated 48 h after implant removal without regard to estrus. Calves were removed for 48 h following implant removal. Each year a group of cows was randomly selected from the BE group (n = 8, 1985; n = 7, 1986) and NE group (n = 8, 1985; n = 7, 1986) and cannulated at estrus after SMB implant removal. Blood samples were collected at 15-min intervals for 2 h and every 2 h for 46 h for determination of LH concentrations. Bull-exposed cows returned to estrus 16 d earlier (P < 0.01) than NE cows in 1985. In 1986, no difference was observed between BE and NE cows for days from calving to first estrus. The percentage of cows exhibiting estrus prior to synchronization was greater (P < 0.01) for BE cows than NE cows in 1985 (78 vs. 17%) and in 1986 (75 vs. 24%). Peak LH levels did not differ between treatment but were different between years. Time to the LH peak following SMB implant removal and calf removal did not differ between treatment and year. Conception rates were not influenced by bull exposure or year. Days from calving to conception were also not influenced by bull exposure. Key words: Bull exposure, cows, postpartum interval, reproduction
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Cavestany, D., N. Negrin, R. Negrin i J. F. Groth. "Response of beef heifers and non-suckling beef cows to different oestrous synchronization protocols". Animal Science 74, nr 3 (czerwiec 2002): 547–52. http://dx.doi.org/10.1017/s135772980005270x.
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AbstractThe objective was to evaluate different oestrous synchronization schemes in beef cattle under range conditions. In experiment 1, 202 heifers averaging 26 months of age were assigned randomly to three treatments: (a) GnRH-PG. (no. = 44) day 0 (D0): injection of GnRH; D7: injection of PGF2α; D0 to D25 oestrous detection (OD) and artificial insemination (AI); (b) OD-PG. (no. = 45) D0 to D4; OD + AI; D5: injection of PGF2α; D5 to D25 OD + AI; and (c)Ovsynch. (no. = 113) D0: injection of GnRH; D7: injection of PGF2α; D9: injection of GnRH and 16 h later AI at fixed time. In experiment 2, 318 non-suckling cows were assigned randomly to three treatments: (a) GnRH-PG. (no. = 106) D0: injection of GnRH; D7: injection of PGF2α; D0 to D25 OD + AI; (b) GnRH-MAP-PG. (no. = 106) D0: injection of a GnRH analogue and insertion of an intravaginal sponge impregnated with 250 mg of medroxyprogesterone acetate; D7: injection of PGF2α and sponge withdrawal; D0 to D25 OD + AI; (c) controls. (no. = 106) OD and AI. The experimental period lasted 25 days and, with exception of the Ovsynch treatment, oestrous detection was carried out twice a day (a.m./p.m.) and inseminations performed 12 h later. The pregnancy rates assessed by ultrasonography 30 days after AI were: experiment 1: (a) 30·0%; (b) 28·6% and (c) 62·3% (P < 0·05); experiment 2: (a) 60·2%; (b) 57·8% and (c) 45·5% (P < 0·05). It is concluded that in heifers and non-suckling cows, oestrous synchronization treatments result in higher pregnancy rates. In non-suckling cows, the addition of a progestagen did not improve the response.
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Lopes, Sidnei Antônio, Mário Fonseca Paulino, Edenio Detmann, Luciana Navajas Rennó, Ériton Egídio Lisboa Valente, Carla Heloísa Avelino Cabral, Victor Valério de Carvalho, Josilaine Aparecida da Costa Lima, Marcos Rocha Manso i Hugo Colombarolli Bonfá. "Evaluation of grazing beef cows receiving supplements with different protein contents". Semina: Ciências Agrárias 37, nr 5 (26.10.2016): 3361. http://dx.doi.org/10.5433/1679-0359.2016v37n5p3361.
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The aim of this study was to evaluate the effects of supplementation with different crude protein contents on the productive performance of grazing beef cows during post-calving. Thirty-six beef cows, with age and average body weight of 5 years and 490±17.9 kg, respectively, were used. The experimental design was completely randomized. The treatments were: control = cows received only mineral mixture ad libitum; supplemented = cows received 1 kg d-1 of supplement containing 80, 200, or 320 g crude protein (CP) kg-1. There was no effect (P ? 0.16) of supplementation on voluntary intake. A linear effect (P < 0.02) of the CP content in the supplements was observed among supplemented cows, only for the CP intake. Supplementation did not affect (P ? 0.20) the total digestibility of organic matter, neutral detergent fiber corrected for ash and protein, and CP. Among supplemented cows, a positive linear effect (P < 0.01) of the CP content in the supplement was observed for the CP digestibility. Intestinal flow of microbial nitrogen compounds and efficiency of synthesis microbial were not affected (P ? 0.18) by treatments. Performance, milk yield and composition were not also affected (P ? 0.11) by treatments. Supplementation did not affect (P ? 0.52) non-esterified fatty acids, urea nitrogen and progesterone serum concentrations. It is concluded that supplementation of grazing beef cows during post-calving does not affect nutritional and productive performance.
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Frasier, W. Marshall, i George H. Pfeiffer. "Optimal Replacement and Management Policies for Beef Cows". American Journal of Agricultural Economics 76, nr 4 (listopad 1994): 847–58. http://dx.doi.org/10.2307/1243746.
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Hopman, Bruce, i Dale W. Weber. "Effect of Lasalocid on Fall-Calving Beef Cows". Journal of Animal Science 63, nr 6 (1.12.1986): 1722–27. http://dx.doi.org/10.2527/jas1986.6361722x.
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Chang, Ching-Fong, i Jerry J. Reeves. "Postpartum Interval in Beef Cows Shortened by Enclomiphene2". Journal of Animal Science 65, nr 1 (1.07.1987): 217–23. http://dx.doi.org/10.2527/jas1987.651217x.
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