Institute for Reproduction of Farm Animals Schönow, Bernauer Allee 10, 16321, Bernau, Germany; Rinder-Union West eG, Schiffahrter Damm 235 A, 48147, Münster, Germany.
Institute for Reproduction of Farm Animals Schönow, Bernauer Allee 10, 16321, Bernau, Germany.
Theriogenology. 2023 Mar 15;199:50-56. doi: 10.1016/j.theriogenology.2023.01.012. Epub 2023 Jan 16.
Low fertility rates in lactating dairy cows as well as restricted availability of semen doses of young bulls with high genetic merit are two major problems in the reproduction of dairy cows. By using liquid semen (LS), the number of doses per ejaculate can be increased. One of the challenges of optimizing the reproductive performance of dairy cows is the phenomenon of variable estrus lengths. The objective of this study was to determine whether the use of LS affects pregnancy outcome of dairy cows with delayed ovulation, when compared with frozen semen (FS). A randomized controlled clinical trial was implemented. In a split-sample procedure, 131 ejaculates were processed into LS (Caprogen, LIC, New Zealand) and FS (BioXcell, IMV, France). Both semen types of each ejaculate were inseminated under the same field conditions to cows showing natural or induced heat. Cows and semen type were allocated according to the last digit of the cows identification number (even = frozen semen, odd = liquid semen). Inseminations (n = 667) were conducted after localization of the pre-ovulatory follicle. Determination of ovulation was performed 24 h post AI per transrectal ultrasonographic examination. Ovulations were classified as delayed when the pre-ovulatory follicle was still present at ovulation control. The prevalence of delayed ovulations was 25.2%. Data of 667 inseminations were analyzed with a generalized linear mixed model including semen type (P = 0.016), parity (P = 0.014), backfat thickness (P = 0.006), estrus induction (P = 0.010), ovulation (P = 0.265) and the interaction term 'semen type by ovulation' (P = 0.094). Overall, a higher pregnancy per AI (P/AI) of LS (45.4%) than P/AI of FS (33.7%) was found. In cases of delayed ovulations, use of LS resulted in higher P/AI (46.8%) compared with FS (27.7%; P = 0.017). We concluded that the fertilizing capacity of LS in prolonged intervals from AI to ovulation might be greater when compared with FS and could be an efficient tool to improve fertility of lactating dairy cows with delayed ovulations.
泌乳奶牛的低生育率以及具有高遗传价值的年轻公牛的精液剂量有限，这是奶牛繁殖的两个主要问题。通过使用液态精液（LS），每次射精的剂量可以增加。优化奶牛繁殖性能的挑战之一是发情持续时间的变化。本研究的目的是确定与冷冻精液（FS）相比，使用 LS 是否会影响延迟排卵奶牛的妊娠结局。实施了一项随机对照临床试验。在分样程序中，将 131 个精液样本处理成 LS（Caprogen，LIC，新西兰）和 FS（BioXcell，IMV，法国）。每个精液样本的两种类型都在相同的田间条件下对表现出自然或诱导发情的奶牛进行授精。根据奶牛识别号码的最后一位数字（偶数=冷冻精液，奇数=液态精液）对奶牛和精液类型进行分配。授精（n=667）在预排卵卵泡定位后进行。通过直肠超声检查每 24 小时进行一次排卵确定。当排卵控制时预排卵卵泡仍然存在时，排卵被分类为延迟。延迟排卵的患病率为 25.2%。使用广义线性混合模型分析了 667 次授精的数据，模型中包含精液类型（P=0.016）、胎次（P=0.014）、背膘厚度（P=0.006）、发情诱导（P=0.010）、排卵（P=0.265）和“精液类型与排卵”的交互项（P=0.094）。总体而言，LS 的每剂妊娠率（P/AI）（45.4%）高于 FS 的 P/AI（33.7%）。在延迟排卵的情况下，与 FS（27.7%）相比，LS 可使 P/AI（46.8%）更高（P=0.017）。我们得出结论，与 FS 相比，LS 在 AI 到排卵之间延长时间内的受精能力可能更强，并且可能是提高延迟排卵泌乳奶牛的一种有效工具。
