Compton C W R, McDougall S
Animal Health Centre, Morrinsville, New Zealand.
N Z Vet J. 2010 Aug;58(4):175-83. doi: 10.1080/00480169.2010.68862.
To describe the reproductive performance and management practices over three lactations in dairy herds that had different policies on the routine use of induction of parturition; to describe any change in outcomes in herds that ceased inductions during the study period; and to investigate other herd-level factors associated with reproductive performance.
From 2002 to 2004 inclusive, a longitudinal study was undertaken in 82 herds in the Waikato region of New Zealand. The main outcome variables were the percentage of cows pregnant after 8 weeks of mating (8-week in-calf rate) and the percentage of cows not pregnant at the end of mating (final empty rate). Data were obtained from pregnancy diagnosis records from a veterinary practice and from an electronic database, and a questionnaire. Herds were classified as either not using inductions in the three lactations (Nil; n=14), ceased inductions in the second or third lactation (Transitional; n=12), or continuing to induce (Continuing; n=56).
Nil herds had a higher 8-week in-calf rate (p=0.01) than Transitional or Continuing herds (83%, 78% and 79%, respectively). The final empty rate in Nil and Transitional herds was similar (10.2% and 9.9%), tended to be greater in Nil than in Continuing herds (10.2% vs 9.0%; p=0.06) and was greater in Transitional than in Continuing herds (9.9% vs 9.0%; p=0.04), respectively. Multivariable modelling found that 8-week in-calf rates were additionally associated with year of lactation, interval from the planned start of calving (PSC) to the median calving date, duration of artificial insemination, and 21-day submission rate; and that final empty rates were associated with year of lactation, predominant breed, percentage of the herd calving within 40 days of the planned start of mating (PSM), the total duration of mating, and the 21-day submission rate, but not the herd induction policy. A change to ceasing routine use of induction tended to be associated (p=0.07) with a 2.5% increase in the final empty rate in the lactation of change.
The reproductive performance of herds was associated with induction policy, in addition to other factors. Herds that ceased induction had a greater 8-week in-calf rate but a greater final empty rate than those that continued. The higher empty rate in Nil herds was partly due to their shorter duration of mating.
Herdowners and their advisors planning to cease routine use of induction should plan for an increase in the final empty rate in both the lactation of change and in the longer term, and undertake measures to mitigate against this effect.
描述对分娩诱导常规使用有不同政策的奶牛场三个泌乳期的繁殖性能和管理实践；描述在研究期间停止诱导的牛群中结果的任何变化；并调查与繁殖性能相关的其他牛群水平因素。
从2002年至2004年（含），在新西兰怀卡托地区的82个牛群中进行了一项纵向研究。主要结果变量是配种8周后怀孕的奶牛百分比（8周怀孕率）和配种结束时未怀孕的奶牛百分比（最终空怀率）。数据来自一家兽医诊所的妊娠诊断记录、一个电子数据库以及一份问卷。牛群被分类为在三个泌乳期都不使用诱导（无诱导组；n = 14）、在第二个或第三个泌乳期停止诱导（过渡组；n = 12）或继续诱导（持续诱导组；n = 56）。
无诱导组的8周怀孕率（p = 0.01）高于过渡组或持续诱导组（分别为83%、78%和79%）。无诱导组和过渡组的最终空怀率相似（10.2%和9.9%），无诱导组的最终空怀率倾向于高于持续诱导组（10.2%对9.0%；p = 0.06），过渡组的最终空怀率高于持续诱导组（9.9%对9.0%；p = 0.04）。多变量建模发现，8周怀孕率还与泌乳年份、从计划产犊开始（PSC）到中位产犊日期的间隔、人工授精持续时间以及21天提交率有关；最终空怀率与泌乳年份、主要品种、在计划配种开始（PSM）后40天内产犊的牛群百分比、配种总持续时间以及21天提交率有关，但与牛群诱导政策无关。改为停止常规诱导往往与变化泌乳期的最终空怀率增加2.5%有关（p = 0.07）。
除其他因素外，牛群的繁殖性能与诱导政策有关。停止诱导的牛群8周怀孕率更高，但最终空怀率高于继续诱导的牛群。无诱导组较高的空怀率部分归因于其较短的配种持续时间。
计划停止常规诱导的牧场主及其顾问应计划在变化泌乳期及长期内提高最终空怀率，并采取措施减轻这种影响。
