Azzam S M, Kinder J E, Nielsen M K, Werth L A, Gregory K E, Cundiff L V, Koch R M
Department of Animal Science, University of Nebraska, Lincoln 68583-0908.
J Anim Sci. 1993 Feb;71(2):282-90. doi: 10.2527/1993.712282x.
Calving records from 1969 to 1989 from the Roman L. Hruska U.S. Meat Animal Research Center were used to investigate how climatic conditions, in addition to dystocia, age of dam, size of calf, and sex affect calf survival from birth to 1 wk of age. Data were analyzed separately for cows calving with (n = 11,094) or without (n = 72,187) dystocia. Neonatal mortality was described by a logit model and parameters were estimated by maximum-likelihood procedures. Calves born to cows with dystocia were five times as likely to die neonatally than calves born without assistance. Of all calves that died, 43.6% were born with difficulty. Of these calves, survival was lowest for those that were small relative to their genetic group, sex, and age of dam. Large calves had markedly increased mortality only when born to 2-yr-old dams. Average ambient temperature and precipitation on day of calving affected survival nonlinearly and the magnitude of the effect depended on age of dam, sex and size of calf, and dystocia incidence. Calves born to 2-yr-old cows were more susceptible to severe weather conditions than calves born to older cows. The negative effect of precipitation on survival increased with decreasing temperature.
利用罗马L. 赫鲁斯卡美国肉用动物研究中心1969年至1989年的产犊记录，研究除难产、母牛年龄、犊牛大小和性别外，气候条件如何影响犊牛从出生到1周龄的存活情况。对有难产（n = 11,094）和无难产（n = 72,187）的母牛所产犊牛的数据分别进行分析。采用logit模型描述新生犊牛死亡率，并通过最大似然法估计参数。难产母牛所产犊牛新生期死亡的可能性是顺产犊牛的五倍。在所有死亡的犊牛中，43.6%是难产出生的。在这些犊牛中，相对于其遗传群体、性别和母牛年龄较小的犊牛存活率最低。只有当犊牛由2岁的母牛所生时，体型较大的犊牛死亡率才会显著增加。产犊当天的平均环境温度和降水量对存活率有非线性影响，影响程度取决于母牛年龄、犊牛性别和大小以及难产发生率。2岁母牛所产犊牛比年龄较大母牛所产犊牛更容易受到恶劣天气条件的影响。降水量对存活率的负面影响随着温度降低而增加。
