Brownlie T S, Morton J M, Heuer C, Hunnam J, McDougall S
a Cognosco, Anexa Animal Health , Morrinsville , New Zealand.
N Z Vet J. 2014 Mar;62(2):77-86. doi: 10.1080/00480169.2013.848499. Epub 2013 Nov 21.
The primary objective of this study was to describe the reproductive performance of a selection of New Zealand dairy herds in 2009/10 and 2010/11. A secondary objective was to explore associations between a number of biophysical and socio-demographic herd-level variables and herd-level reproductive outcomes.
Seasonal-calving, pasture-based herds from the Waikato (n=16), Taranaki (n=16), North Canterbury (n=17) and South Canterbury (n=14) regions of New Zealand were enrolled as part of a larger study. Submission, conception and pregnancy risks ("in-calf risks") were calculated for 2009/10 and 2010/11 based on cow-level records and from the results of strategically timed pregnancy diagnoses. Additional herd-level information was collected during interviews with the herd key decision maker (KDM). Associations between independent variables and reproductive performance were examined using univariable and multivariable generalised linear models.
Mean 6-week in-calf risk of the herds over both study years was 67 (min 46, max 86)%, mean 3-week submission risk was 81 (min 44, max 95)% and mean probability of pregnancy at first insemination was 48 (min 25, max 71)%. On univariable analyses, the herd's 6-week in-calf risk in the year before enrollment (2008/09) was the strongest identified predictor of each of submission risk, probability of pregnancy at first insemination and 6-week in-calf risk (all p<0.01), while other predictor variables considered were non-significant. From multivariable modelling, herds using extensive production systems had better reproductive performance than more intensively managed systems. Higher 3-week submission risks were achieved in herds where the KDM were farm managers rather than owner operators, and where the predominant breed was Jersey rather than Friesian.
The New Zealand dairy industry has set a target for a mean 6-week in-calf risk of 78%, with minimal hormonal intervention, by 2016. Achieving this target appears unlikely unless there are substantial increases in both submission risks and pregnancy at first inseminations. The mean 6-week in-calf risk of New Zealand dairy herd does not appear to have changed in the last decade. However the large differences between herds indicate that better reproductive performance is currently possible in many herds. The herd's 6-week in-calf risk in the year before enrollment (2008/09) was the strongest identified predictor of current 6-week in-calf risk, suggesting that rate of improvement in reproductive performance would be slow within current management systems unless substantial changes are introduced.
本研究的主要目标是描述2009/10年度和2010/11年度新西兰部分奶牛场的繁殖性能。次要目标是探讨一些生物物理和社会人口统计学的牛群水平变量与牛群水平繁殖结果之间的关联。
作为一项更大规模研究的一部分，招募了来自新西兰怀卡托（n = 16）、塔拉纳基（n = 16）、北坎特伯雷（n = 17）和南坎特伯雷（n = 14）地区的季节性产犊、以牧场为基础的牛群。根据奶牛个体记录以及策略性定时妊娠诊断结果，计算2009/10年度和2010/11年度的提交配种、受孕和怀孕风险（“怀孕风险”）。在与牛群关键决策者（KDM）的访谈中收集了额外的牛群水平信息。使用单变量和多变量广义线性模型检验自变量与繁殖性能之间的关联。
在两个研究年度中，牛群的平均6周怀孕风险为67%（最小值46%，最大值86%），平均3周提交配种风险为81%（最小值44%，最大值95%），首次配种时的平均怀孕概率为48%（最小值25%，最大值71%）。在单变量分析中，入组前一年（2008/09）牛群的6周怀孕风险是提交配种风险、首次配种时怀孕概率和6周怀孕风险中最强的已识别预测指标（所有p < 0.01），而其他考虑的预测变量无统计学意义。多变量建模显示，采用粗放生产系统的牛群繁殖性能优于管理更集约的系统。在关键决策者是农场经理而非业主经营者的牛群以及主要品种是泽西牛而非弗里生牛的牛群中，3周提交配种风险更高。
新西兰乳业设定了到2016年平均6周怀孕风险达到78%且激素干预最少的目标。除非提交配种风险和首次配种时的怀孕率大幅提高，否则实现这一目标似乎不太可能。过去十年中，新西兰奶牛群的平均6周怀孕风险似乎没有变化。然而，牛群之间的巨大差异表明，目前许多牛群的繁殖性能有提升空间。入组前一年（2008/09）牛群的6周怀孕风险是当前6周怀孕风险最强的已识别预测指标，这表明在当前管理系统中，除非引入重大变革，繁殖性能的改善速度将很慢。
