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.
All Science Journal Classification (ASJC) codes
- Animal Science and Zoology