Variability of daily milk yield during the first 100 days of lactation in Holstein cows

KAŠNÁ, Eva, ZAVADILOVÁ, Ludmila a VAŘEKA, Jan., 2023 Variability of daily milk yield during the first 100 days of lactation in Holstein cows. In Book of Abstracts of the 74rd Annual Meeting of the EAAP, Book of abstracts No. 29, 26 August - 1 September, 2023, Lyon, France. The Netherlands: Wageningen Academic Press, s. n. ISSN
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Fluctuations in daily milk yield (DMY) can be used as an indicator of the health and resilience of dairy cows. We evaluated the variability of DMY during the first 100 days of lactation in cows from three cooperating farms. The dataset included 75,000 DMY records of 548 Holstein cows. The data were collected between October 2022 and January 2023. Cows were required to have records for at least 20 successive days and the first day in milk (DIM) must have been lower than 50. DMY ranged between 1 and 78 kg with a mean of 36 kg of milk per cow and day. The variances of DMY for each cow were log-transformed (LnVar) to achieve their normal distribution. The estimation of heritability (h2=0.15) and breeding values (BV) for LnVar was based on a single trait linear animal model and performed with the BLUPF90 family of programs. The model included fixed effects of the farm, the month of calving, the lactation order and the first observed DIM, the random effect of animals included in the three-generation pedigree and the random residual. We calculated the correlations of sires’ BV for LnVar with their BV for production, fertility, exterior and health traits to indicate their possible genetic correlations. The higher BV(LnVar) were associated with the higher BV for milk, fat and protein yield (kg), and the lower BV for milk protein and fat content (%). The higher BV(LnVar) were related to the deep and wide rear udder and negatively correlated with locomotion, a final class for legs and feet and body condition score. The lower LnVar was associated with better longevity and fertility traits, but the correlations were non-significant. The lower BV(LnVar) were also favourably correlated with health traits BV (somatic cells count, retained placenta, metritis, ovarian cysts, clinical mastitis, ketosis, feet disorders) but the correlations were weak and non-significant. The study was supported by the Ministry of Agriculture of the Czech Republic, project QK22020280 and institutional support MZE-RO0723.

ProjektVyužití genomické selekce pro optimalizaci resilience dojeného skotu, Dlouhodobý koncepční rozvoj výzkumné organizace
OdděleníGenetika a šlechtění hospodářských zvířat