The availability of daily milk yield (dMY) allows for analyses of additional traits that could be related to cow fitness. The objectives of this study were to determine heritability of day-to-day variation in milk yield and estimate correlations of variability with genomic PTA for commonly measured production, health, and fertility traits. Daily milk yield records were retrieved for 2,377 lactations of 1,190 Holsteins from a single herd and used to derive absolute change (ΔABS) in dMY, residual absolute change (rABS) which was derived by regressing ΔABS on dMY, and the standard deviation of dMY (sdMY). Values from 5 to 200 days in milk were retained and averaged for each trait. Estimated breeding values were merged with official genomic PTA for 464 cows. Heritability estimates were 0.23±0.05, 0.20±0.04, 0.10±0.03, and 0.15±0.04 for dMY, ΔABS, sdMY, and rABS, respectively. Both ΔABS (0.68±0.9) and sdMY (0.61±0.15) were strongly correlated genetically with dMY, whereas dMY and rABS were independent (0.13±0.17). Higher gEBV for dMY, ΔABS, sdMY, or rABS was unfavorably correlated with PTA for health and fertility traits. Daily milk yield variability was heritable and cows with less variability had improved fitness; rABS was more independent of dMY than ΔABS or sdMY.

每日牛奶产量（dMY）的可用性可用于分析可能与牛的体质有关的其他特征。这项研究的目的是确定牛奶产量日常变化的遗传力，并估计变异性与基因组PTA的相关性，以用于通常测量的生产，健康和生育性状。每天从1个牛群中提取2 377次泌乳的每日产奶量记录，并用于得出dMY中的绝对变化（ΔABS），通过对dMY上的ΔABS进行回归得到的剩余绝对变化（rABS）以及dMY（ sdMY）。保留牛奶中5到200天的值，并对每个特征取平均值。将估计的育种价值与官方的464头母牛基因组PTA合并。对于dMY，ΔABS，sdMY，遗传力估计值分别为0.23±0.05、0.20±0.04、0.10±0.03和0.15±0.04，和rABS。ΔABS（0.68±0.9）和sdMY（0.61±0.15）都与dMY密切相关，而dMY和rABS是独立的（0.13±0.17）。dMY，ΔABS，sdMY或rABS较高的gEBV与PTA的健康和生育特征不利相关。每日产奶量的变异性是可遗传的，变异性较小的母牛的体质有所改善。rABS比ΔABS或sdMY更独立于dMY。