Department of Animal and Dairy Sciences, University of Wisconsin, Madison 53706.
Italian Brown Breeders Association, Bussolengo, Verona 37012, Italy.
J Dairy Sci. 2021 Oct;104(10):10896-10904. doi: 10.3168/jds.2021-20332. Epub 2021 Jul 23.
Dairy bull fertility is traditionally evaluated using semen production and quality traits; however, these attributes explain only part of the differences observed in fertility among bulls. Alternatively, bull fertility can be directly evaluated using cow field data. The main objective of this study was to investigate bull fertility in the Italian Brown Swiss dairy cattle population using confirmed pregnancy records. The data set included a total of 397,926 breeding records from 1,228 bulls and 129,858 lactating cows between first and fifth lactation from 2000 to 2019. We first evaluated cow pregnancy success, including factors related to the bull under evaluation, such as bull age, bull inbreeding, and AI organization, and factors associated with the cow that receives the dose of semen, including herd-year-season, cow age, parity, and milk yield. We then estimated sire conception rate using only factors related to the bull. Model predictive ability was evaluated using 10-fold cross-validation with 10 replicates. Interestingly, our analyses revealed that there is a substantial variation in conception rate among Brown Swiss bulls, with more than 20% conception rate difference between high-fertility and low-fertility bulls. We also showed that the prediction of bull fertility is feasible as our cross-validation analyses achieved predictive correlations equal to 0.30 for sire conception rate. Improving reproduction performance is one of the major challenges of the dairy industry worldwide, and for this, it is essential to have accurate predictions of service sire fertility. This study represents the foundation for the development of novel tools that will allow dairy producers, breeders, and artificial insemination companies to make enhanced management and selection decisions on Brown Swiss male fertility.
传统上，通过精液产量和质量性状来评估奶牛的繁殖力；然而，这些特征仅能解释公牛之间繁殖力差异的一部分。或者，可以直接使用奶牛场数据来评估公牛的繁殖力。本研究的主要目的是使用确认妊娠记录来调查意大利棕色瑞士奶牛群体中的公牛繁殖力。该数据集包括 2000 年至 2019 年间，来自 1228 头公牛和 129858 头处于第一至第五泌乳期的泌乳奶牛的总计 397926 次配种记录。我们首先评估了奶牛的妊娠成功率，包括与评估公牛相关的因素，如公牛年龄、公牛近亲繁殖和人工授精组织，以及与接受精液剂量的奶牛相关的因素，包括 herd-year-season、奶牛年龄、胎次和产奶量。然后，我们仅使用与公牛相关的因素来估计 sire 受孕率。使用 10 折交叉验证和 10 个重复来评估模型预测能力。有趣的是，我们的分析表明，棕色瑞士公牛的受孕率存在很大差异，高繁殖力和低繁殖力公牛之间的受孕率差异超过 20%。我们还表明，公牛繁殖力的预测是可行的，因为我们的交叉验证分析实现了 sire 受孕率的预测相关性等于 0.30。提高繁殖性能是全球奶牛养殖业的主要挑战之一，因此，准确预测服务 sire 的繁殖力至关重要。本研究为开发新工具奠定了基础，这些新工具将使奶牛生产者、饲养者和人工授精公司能够在棕色瑞士公牛奶牛的繁殖力方面做出更好的管理和选择决策。
