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.

中文翻译：

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肉牛繁殖力：管理实践和技术进步的重要性


替代小母牛的开发是牛犊牛肉生产系统的核心。据美国农业部国家农业统计局报告，2020 年，有 577.1 万头 500 磅及以上的小母牛正在培育中，以替代母牛。多项研究数据汇编表明，85% 至 95% 的小母牛将在第一个繁殖季节怀孕。饲养数千头用于替代的小母牛可能无法在第一个繁殖季节产下小牛，从而给母牛犊牛生产者造成经济损失。为了最大限度地发挥肉用小母牛的繁殖潜力，已经制定了许多管理程序。这些方法包括但不限于以下方法：控制体重增加的营养管理、通过生理和形态指标识别生殖成熟度以及实施动情同步计划。管理策略的实施对小母牛的繁殖效率具有重要的积极影响。然而，这也有局限性，因为一些被认为准备好进入第一个繁殖季节的小母牛并没有怀孕。与此同时，肉牛生育力相关性状的遗传选择并没有促进这一特定领域的重大遗传收益，很可能是由于牛的雌性生育力性状遗传力较低。正在研究窦卵泡计数、DNA 基因分型和 RNA 分析等技术，以帮助识别低生育潜力的小母牛。迄今为止，许多多态性已与小母牛的生育能力相关，但尚未在牛群中鉴定出 DNA 标记。 窦卵泡计数是卵巢储备的指标，也是小母牛生殖健康的指标。我们一直致力于鉴定与妊娠结局相关的小母牛转录组谱。我们目前整合蛋白质编码转录本丰度和人工智能的研究已经确定了血源性转录本丰度可用作肉牛生育潜力指标的潜力。总之，母牛生产系统面临着降低成本和提高效率的持续压力，而新技术可以帮助减少肉用小母牛繁殖力方面长期存在的限制。