摘要
Reproductive efficiency in the Western Canadian beef cow herd has not improved over the past 3 decades, despite consistent and measurable improvement in several related areas of production. The general objective of this thesis was to evaluate the relationships between early-observation traits (feeding behaviour), weight change, and reproductive efficiency in beef cows. Estimates of total dry matter intake and the relationship between residual feed intake (adjusted for body composition; RFIFAT) observed in heifers and mature cows were also evaluated as traits of interest and use to the Canadian beef industry. Chapters 3 and 4 investigated the relationship between feeding behaviours and reproductive efficiency and provided phenotypic and genetic correlations that may be of use in selecting heifers with greater reproductive potential if those heifers have feeding behaviours reported. Feeding behaviour and reproductive efficiency were both correlated with dry matter intake; feeding behaviours that promote dry matter intake may be useful in the identification of heifers with greater reproductive potential. Chapter 5 evaluates the usefulness of tracking cow weights over time and the usefulness of comparing cow weights to an idealized growth curve estimation. Generally, cows that gained weight over time were more likely to be culled for reproductive failure, and the same was true for cows that were heavier than their estimated body weight. Producers may be able to use weight-monitoring technology currently available and in development to identify cows that abort their calves after a positive pregnancy evaluation and remove them from their herd at a time when feed resources are expensive. Chapter 6 was a comprehensive and unique estimation of cow dry matter intake over time, including energy estimates based on birth, weaning, residual feed intake tests as a heifer and as a cow, and subsequent calving events with associated energy expenditures for milk production. These estimates were compared to genomic retained heterozygosity, breed composition, and winter-feeding environment to evaluate the effects of those variables on dry matter intake predictions. Chapter 7 investigated the relationship between heifer residual feed intake and residual feed intake observed in the same animals as mature cows. Residual feed intake in heifers can be used to select cows that maintain a proportion of their efficiency observed as heifers, and ultimately provides evidence that the selection of feed-efficient heifer calves as replacement animals should result in a more efficient mature cow herd.
This thesis provided evidence to support the selection of heifer replacements using feeding behaviours observed during a feed intake test, the use of weight monitoring technology to identify cows that may have had reproductive issues. This thesis also provided some of the first estimates of dry matter intake over the course of the production cycle in a large number of animals under normal production environments and provided estimates of the relationship between heifer and cow residual feed intake.
摘要译文
尽管在几个相关的生产领域，在过去的30年中，在过去30年中，在过去的30年中，在过去的30年中，生殖效率尚未提高。本论文的一般目标是评估牛肉母牛的早期观察特征（喂养行为），体重变化和生殖效率之间的关系。在小母牛和成熟的母牛中观察到的总干物质摄入量的估计以及残留的饲料摄入量（针对身体成分调整）之间的关系是感兴趣的特征和对加拿大牛肉工业的使用的特征。第3章和第4章研究了喂养行为与生殖效率之间的关系，并提供了表型和遗传相关性，如果这些小母牛报告了喂养行为，则可以在选择具有更大生殖潜力的小母牛时使用。进食行为和生殖效率都与干物质摄入相关。促进干物质摄入的喂养行为可能对鉴定具有更大生殖潜力的小母牛有用。第5章评估了随着时间的推移跟踪牛重量的有用性，以及将牛重与理想化的生长曲线估计的有用性。通常，随着时间的流逝，体重增加的母牛更有可能因生殖失败而被淘汰，而对于比估计的体重重的母牛也是如此。生产商也许能够使用当前可用的重量监控技术，并在开发中识别出阳性妊娠评估后流产小牛的奶牛，并在饲料资源昂贵的时候将其从群中删除。第6章是对牛干物质摄入量的全面且独特的估计，包括基于出生，断奶，残留的饲料摄入测试作为小母牛和牛的残留饲料摄入测试，以及随后的产犊事件，以及与牛奶生产相关的能源支出。将这些估计值与基因组保留的杂合性，繁殖组成和冬季喂养环境进行了比较，以评估这些变量对干物质摄入预测的影响。第7章研究了小母牛残留的饲料摄入量与与成熟母牛相同的动物中观察到的残留饲料摄入量之间的关系。小母牛中的残留饲料摄入量可用于选择维持小母牛效率的一部分的母牛，并最终提供证据表明，选择饲养效率的小母牛犊牛作为替代动物的选择应导致更有效的成熟牛群。该论文提供了证据，以支持使用饲料摄入测试期间观察到的喂养行为，使用体重监测技术来识别可能存在生殖问题的母牛的选择。该论文还提供了在正常生产环境下大量动物的整个生产周期过程中对干物质摄入量的一些首次估计，并提供了小母牛和牛残余饲料摄入之间的关系的估计。
Olson, Cameron A. Identification of feed intake traits related to beef reproductive improvement[D]. CA: University of Alberta, 2022