Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
Theriogenology. 2013 Apr 15;79(7):1083-94. doi: 10.1016/j.theriogenology.2013.02.004. Epub 2013 Mar 6.
To identify herd management and cow characteristics associated with the reproductive success of cow-calf herds in Western Canada, 33,391 beef cows were followed from the beginning of the breeding season in 2001 through pregnancy testing in 2002. Breeding management and cow-level risk factors such as age, body condition score (BCS), and previous reproductive history, were measured through a series of herd visits by project personnel and records maintained by the herd owner. Pregnancy status was measured in 205 herds in the fall of 2001 and again in 200 herds in the fall of 2002. Cows least likely to be pregnant in the fall of the year were 10 years old or older, exposed to a bull less than 84 days, had a BCS ≤5 of 9 at pregnancy testing, <5 of 9 before calving, and lost condition between calving and the start of the breeding season, or had a prebreeding BCS <5 of 9 with a loss of condition between breeding and pregnancy testing. Other factors identified that decreased the likelihood of pregnancy in at least one of the 2 years included being a heifer or being a cow exposed to breeding after her first calf, and using a single bull on breeding pasture. Cows vaccinated for bovine viral diarrhea virus and infectious bovine rhinotracheitis and bred on community pastures were more likely to be pregnant than cows that were not vaccinated and bred on community pastures. Cows bred on community pastures that were not vaccinated were also less likely to be pregnant than cows that were not on community pastures regardless of vaccination status. Calving-associated events such as twin birth, Cesarean section or malpresentation, problems such as uterine prolapse or retained placentas, abortion or calf death within 1 hour after birth, or calving late after the start of the breeding season, were also associated with fewer pregnancies after accounting for all other factors.
为了确定与加拿大西部奶牛-小牛群繁殖成功率相关的牛群管理和奶牛特征，我们对 33391 头肉牛进行了跟踪研究，从 2001 年配种季节开始，到 2002 年妊娠检测结束。通过项目人员对牛群的一系列访问和牛群所有者保存的记录，测量了配种管理和奶牛个体的风险因素，如年龄、体况评分（BCS）和以前的繁殖史。2001 年秋季在 205 个牛群中测量了妊娠状况，2002 年秋季在 200 个牛群中再次测量。在当年秋季最不可能怀孕的奶牛是 10 岁或以上的奶牛，配种时接触公牛的时间少于 84 天，妊娠检测时 BCS≤5，分娩前 BCS<5，分娩后至配种季节开始时体重减轻，或配种前 BCS<5，配种至妊娠检测期间体重减轻。在至少 1 年中降低怀孕可能性的其他因素包括是小母牛或首次产犊后配种的奶牛，以及在繁殖牧场使用单一公牛配种。接种牛病毒性腹泻病毒和传染性牛鼻气管炎疫苗并在社区牧场配种的奶牛比未接种疫苗并在社区牧场配种的奶牛更有可能怀孕。未接种疫苗且在社区牧场配种的奶牛比不在社区牧场配种的奶牛怀孕的可能性更小，无论疫苗接种状况如何。与分娩相关的事件，如双胞胎分娩、剖腹产或胎位不正、子宫脱垂或胎盘滞留等问题、流产或犊牛出生后 1 小时内死亡、或配种季节开始后分娩时间晚，在考虑了所有其他因素后，也与怀孕次数较少有关。
