ABSTRACT In New Zealand, a specific selection scheme for the dairy cattle population milked once-a-day (OAD) has not been implemented. This study aims to investigate estimated genetic progress for different selection objectives based on selection scheme designs using progeny testing (PT) and genomic selection (GS) in OAD herds. Under a PT-scheme, estimated genetic progress ranged from 7 to 45 kg/year (milk), 2.18–2.24 kg/year (fat), and 0.83–1.71 kg/year (protein). Conversely, genetic gains resulting from selecting bulls generated in twice-a-day (TAD) milking systems and used to inseminate cows in OAD herds, ranged between 12 and 52 kg/year (milk), 2.34 and 3.22 kg/year (fat) and 0.83 and 2.29 kg/year (protein). Correlated responses tend to be greater in the yield traits when the emphasis on fertility, residual survival and body condition score were reduced in the selection objective. Further correlated responses in yield traits were reduced when type-related traits were included in the selection objective, in particular when bulls were tested in TAD systems. A more immediate and profitable alternative might be the implementation of a GS-scheme, that would result in a faster genetic gain in the aggregate breeding value or merit for all the traits included in the selection objective (0.310–0.368 vs 0.191–0.196 σg/yr).

中文翻译：

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新西兰每天挤奶一次的奶牛选择方案设计：确定性方法

摘要 在新西兰，尚未实施针对每天挤奶一次 (OAD) 的奶牛种群的特定选择计划。本研究旨在利用 OAD 畜群中的后代检测 (PT) 和基因组选择 (GS)，基于选择方案设计，调查不同选择目标的估计遗传进展。在 PT 方案下，估计的遗传进展范围为 7 至 45 公斤/年（牛奶）、2.18 至 2.24 公斤/年（脂肪）和 0.83 至 1.71 公斤/年（蛋白质）。相反，选择每天两次 (TAD) 挤奶系统中产生并用于为 OAD 牛群中的奶牛授精的公牛所产生的遗传收益介于 12 至 52 公斤/年（牛奶）、2.34 至 3.22 公斤/年（脂肪）之间和 0.83 和 2.29 公斤/年（蛋白质）。当强调生育力时，产量性状的相关反应往往更大，在选择目标中，剩余存活率和身体状况评分降低。当类别相关的特征被包括在选择目标中，特别是当在TAD系统中测试公牛时，进一步相关的响应。更直接和有利可图的替代方案可能是实施 GS 计划，这将导致选择目标中包含的所有性状的总育种价值或优点的遗传增益更快（0.310–0.368 vs 0.191–0.196 σg/年）。