VetEnt, 49 Benson Road, Te Awamutu, New Zealand, 3800.
VetEnt, 49 Benson Road, Te Awamutu, New Zealand, 3800.
J Dairy Sci. 2017 Oct;100(10):8347-8357. doi: 10.3168/jds.2017-12793. Epub 2017 Aug 9.
The aims of this study were to (1) estimate the perinatal (birth to 24 h) and postnatal (∼24 h to the mean weaning age of 13 wk) mortality risk in pasture-based dairy calves until weaning, and (2) identify associated risk factors in the 2015 calving season. A prospective survey of 32 seasonal calving dairy farms was undertaken. Farmers recorded (daily) the number and sex of the calves alive or dead in the paddocks where cows calved. All daily animal movements in and out of the calf rearing facilities, including death and euthanasia, and the identification of the animals (if applicable) were recorded, and a survey of the farm management practices was undertaken. Individual and farm-level risk factors for perinatal mortality were modeled separately using generalized logistic mixed models with a random effect fitted for herd. Postnatal mortality incidence risk was calculated using time at risk for each calf from 24 h of age, collapsed into weeks, and multiplying the incidence risk by the mean weaning age of the study population. Farm-level risk factors contributing to postnatal mortality in the first week of life were assessed using a multivariable logistic mixed regression model. The mean perinatal mortality risk was 5.7% (95% confidence interval 5.4 to 6.1%) with a range from 2.2 to 8.6% (18,437 calves, 30 farms). Perinatal calf mortality was greater for male relative to female calves (odds ratio 1.39; 95% confidence interval 1.22 to 1.59), calves born in the first week of the calving period in comparison to wk 2 to 11 (odds ratio 0.32 to 0.66), and those born on days with greater rainfall (odds ratio 1.01 per 1 mm increase; 95% confidence interval 1.00 to 1.02). At the farm level, perinatal mortality increased for every extra week of calving period length (odds ratio 1.12; 95% confidence interval 1.06 to 1.17). The mean postnatal mortality risk was 4.1% (95% confidence interval 3.6 to 4.6%) with a range of 0 to 11% between farms. Farm-level risk factors contributing to mortality in the first week of life included farmer-reported disease problems in calves (odds ratio 2.2; 95% confidence interval 1.62 to 2.96), or calves hand-fed colostrum in the first 12 h of life (odds ratio 1.66; 95% confidence interval 1.26 to 2.19), which was assumed to be associated with poor colostrum quality and bacterial contamination. Regional differences were also observed in both perinatal and postnatal mortality risks, indicating that weather conditions, herd size, and management variations contribute to mortality incidence. In summary, the mortality risk of perinatal calves and postnatal calves until weaning on pasture-based farms is comparable with data published from other dairying systems despite the notable management differences. Several risk factors were identified that could be managed to reduce mortality incidence of dairy calves.
（1）估计哺乳期（出生至 24 小时）和产后（约 24 小时至 13 周平均断奶年龄）牧场奶牛的死亡风险，直至断奶，（2）确定 2015 年产犊季节的相关风险因素。对 32 个季节性产犊奶牛场进行了前瞻性调查。农民记录了产犊牛群中存活或死亡的小牛的数量和性别（每天）。所有进出犊牛饲养设施的动物日常活动，包括死亡和安乐死，以及动物的识别（如果适用）都有记录，并对农场管理实践进行了调查。使用广义逻辑混合模型分别对围产期死亡的个体和农场级风险因素进行建模，其中对畜群进行了随机效应拟合。产后死亡率的风险是根据每只小牛从 24 小时龄开始的风险时间计算的，按周汇总，并将发病率乘以研究人群的平均断奶年龄。使用多变量逻辑混合回归模型评估了产后第一周内导致死亡的农场级风险因素。围产期死亡率的平均值为 5.7%（95%置信区间 5.4%至 6.1%），范围为 2.2%至 8.6%（18437 头小牛，30 个农场）。与雌性小牛相比，雄性小牛的围产期死亡率更高（优势比 1.39；95%置信区间 1.22 至 1.59），在产犊期第一周出生的小牛与第 2 周至第 11 周出生的小牛相比（优势比 0.32 至 0.66），出生在降雨较多的日子的小牛（每增加 1 毫米降雨量的优势比为 1.01；95%置信区间为 1.00 至 1.02）。在农场层面，产犊期每延长一周，围产期死亡率就会增加（优势比 1.12；95%置信区间 1.06 至 1.17）。产后死亡率的平均值为 4.1%（95%置信区间 3.6%至 4.6%），农场之间的死亡率范围为 0%至 11%。导致产后第一周死亡的农场级风险因素包括农民报告的犊牛疾病问题（优势比 2.2；95%置信区间 1.62 至 2.96），或犊牛在生命的前 12 小时被人工喂养初乳（优势比 1.66；95%置信区间 1.26 至 2.19），这被认为与初乳质量差和细菌污染有关。围产期和产后死亡率也存在区域差异，表明天气条件、畜群规模和管理差异都会导致死亡率的发生。总之，尽管管理差异显著，但基于牧场的奶牛的围产期和产后直至断奶的死亡率风险与其他奶牛养殖系统公布的数据相当。已经确定了一些可以降低奶牛死亡率的风险因素。
