Moorey Sarah E, Biase Fernando H
Department of Animal Science, University of Tennessee, Knoxville, TN USA.
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, 175 West Campus Drive, Blacksburg, VA 24061 USA.
J Anim Sci Biotechnol. 2020 Oct 1;11:97. doi: 10.1186/s40104-020-00503-9. eCollection 2020.
The development of replacement heifers is at the core of cow-calf beef production systems. In 2020, the USDA, National Agricultural Statistics Service reported 5.771 million beef heifers, 500 pounds and over, are under development for cow replacement. A compilation of data from several studies indicate that between 85% and 95% of these heifers will become pregnant in their first breeding season. Several thousands of heifers being raised for replacement may not deliver a calf on their first breeding season and result in economic losses to cow-calf producers. Many management procedures have been developed to maximize the reproductive potential of beef heifers. Such approaches include, but are not limited to the following: nutritional management for controlled weight gain, identification of reproductive maturity by physiological and morphological indicators, and the implementation of an estrous synchronization program. The implementation of management strategies has important positive impact(s) on the reproductive efficiency of heifers. There are limitations, however, because some heifers deemed ready to enter their first breeding season do not become pregnant. In parallel, genetic selection for fertility-related traits in beef heifers have not promoted major genetic gains on this particular area, most likely due to low heritability of female fertility traits in cattle. Technologies such as antral follicle counting, DNA genotyping and RNA profiling are being investigated as a means to aid in the identification of heifers of low fertility potential. To date, many polymorphisms have been associated with heifer fertility, but no DNA markers have been identified across herds. Antral follicle count is an indication of the ovarian reserve and is an indicator of the reproductive health of a heifer. We have been working on the identification of transcriptome profiles in heifers associated with pregnancy outcome. Our current investigations integrating protein-coding transcript abundance and artificial intelligence have identified the potential for bloodborne transcript abundance to be used as indicators of fertility potential in beef heifers. In summary, there is an ongoing pressure for reducing costs and increasing efficiency in cow-calf production systems, and new technologies can help reduce the long-standing limitations in beef heifer fertility.
后备小母牛的培育是肉牛犊牛生产系统的核心。2020年，美国农业部国家农业统计局报告称，有577.1万头体重500磅及以上的肉牛后备小母牛正在培育，用于母牛替代。多项研究的数据汇总表明，这些后备小母牛中有85%至95%将在第一个繁殖季节怀孕。数千头用于替代的后备小母牛可能在第一个繁殖季节无法产犊，给肉牛犊牛生产者造成经济损失。人们已经制定了许多管理程序，以最大限度地提高肉牛后备小母牛的繁殖潜力。这些方法包括但不限于以下几点：控制体重增加的营养管理、通过生理和形态指标确定生殖成熟度以及实施发情同步程序。管理策略的实施对后备小母牛的繁殖效率有重要的积极影响。然而，也存在局限性，因为一些被认为准备进入第一个繁殖季节的后备小母牛并未怀孕。与此同时，肉牛后备小母牛与繁殖力相关性状的基因选择在这一特定领域并未带来重大的遗传进展，这很可能是由于牛的雌性繁殖力性状遗传力较低。诸如窦卵泡计数、DNA基因分型和RNA分析等技术正在作为一种辅助手段进行研究，以识别繁殖力潜力较低的后备小母牛。迄今为止，许多多态性与后备小母牛的繁殖力相关，但尚未在不同牛群中鉴定出DNA标记。窦卵泡计数是卵巢储备的一个指标，也是后备小母牛生殖健康的一个指标。我们一直在致力于识别与怀孕结果相关的后备小母牛转录组图谱。我们目前将蛋白质编码转录本丰度与人工智能相结合的研究已经确定，血液中转录本丰度有潜力用作肉牛后备小母牛繁殖力潜力的指标。总之，肉牛犊牛生产系统在降低成本和提高效率方面一直面临压力，新技术有助于减少肉牛后备小母牛繁殖力方面长期存在的局限性。
