Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, 8146 Dep., 0033, Oslo, Norway.
Acta Vet Scand. 2023 Jun 9;65(1):20. doi: 10.1186/s13028-023-00685-y.
The timing of artificial insemination is critical to achieve acceptable results in cattle production systems. Over the past 60 years the length and expression of oestrus in dairy cattle has altered. Recent studies have indicated the optimal timing for insemination after the commencement of oestrus may now be earlier than traditional recommendations in beef cattle, as is the case in dairy cattle. The aim of the current study was to evaluate the effect of time from onset of oestrus [as determined by an automated activity monitoring system (AAMS)] to artificial insemination (AI) on pregnancy outcome in Norwegian beef cattle. Five commercial beef suckler herds participated in a cohort study by providing data on the time of AAMS alarm and time of AI. Blood sampling on the day of AI was performed and serum progesterone concentration measured. Pregnancy detection was performed by transrectal ultrasonography and aging of the fetus performed when necessary. A mixed logistic regression model was fitted to study the effect of time from AAMS alarm to AI on pregnancy outcome. Time categories used in the model were < 12 h, 12-24 h, and > 24 h.
AI periods (n = 229) with serum progesterone concentration < 1 ng/mL were available for analysis. Overall pregnancy risk per AI for the whole study period was 65.5%, with an inter-herd variation from 10 to 91%. Median time elapsed from AAMS alarm to AI was 17.75 h. Herd affected pregnancy outcome (P = 0.001), while breed and parity status (heifer/cow) did not. The time category closer to AAMS alarm 0-12 h showed a numerically lower pregnancy risk as compared to the baseline group which had AI 12-24 h after onset of oestrus.
This study found no evidence to support a change in the recommended timing of AI in beef suckler cows.
人工授精的时间对于牛生产系统中获得可接受的结果至关重要。在过去的 60 年中，奶牛的发情持续时间和表现已经发生了变化。最近的研究表明，发情开始后进行授精的最佳时间可能比传统的肉牛推荐时间更早，就像在奶牛中一样。本研究的目的是评估从发情开始到人工授精的时间（通过自动活动监测系统（AAMS）确定）对挪威肉牛妊娠结果的影响。五家商业肉牛养殖场通过提供 AAMS 报警时间和人工授精时间的数据参与了队列研究。在授精当天进行了血液采样，并测量了血清孕激素浓度。通过直肠超声检查进行妊娠检测，并在必要时进行胎儿老化。使用混合逻辑回归模型研究从 AAMS 报警到 AI 的时间对妊娠结果的影响。模型中使用的时间类别为<12 h、12-24 h 和>24 h。
可用于分析的 AI 期（n=229）血清孕激素浓度<1 ng/mL。整个研究期间的整体妊娠风险为 65.5%，不同牛群之间的差异为 10%至 91%。从 AAMS 报警到 AI 的中位数时间为 17.75 小时。牛群影响妊娠结果（P=0.001），而品种和胎次（小母牛/母牛）没有。与发情后 12-24 小时进行 AI 的基线组相比，接近 AAMS 报警 0-12 小时的时间类别显示出较低的妊娠风险。
本研究没有证据支持改变肉牛授精的推荐时间。
