engleski

Estimation of genetic parameters for milking speed for Holstein cattle in Croatia

Milking speed has a growing importance from a dairy management standpoint. Cows with slow milking speed require more labour, while cows with fast milking speed could be in greater risk for udder diseases. Selection is therefore aimed for achieving an optimal milking speed. The aim of this paper was to estimate genetic parameters for milking speed using test-day records of Holstein cattle in Croatia. Data included 51, 266 test-day records for 15, 588 first calving cows taken from the central database of the Croatian Agricultural Agency. Pedigree file consisted of 32, 021 animals. In order to improve the normality, logarithmic transformation for milking speed was used. Variance components where estimated using REML method as implemented in the VCE-6 program. Statistical model included calving season, milking time, and milk class as fixed effects, while age at first calving and days in milk were fitted as covariates. Random effects were: direct additive genetic effect, herd-test-day, and permanent environmental effect. The estimated heritability for milking speed was 0.12±0.01. Permanent environmental effect explained 19% of phenotypic variation, while herd-test-day explained another 17% of variability. The proportion of unexplained phenotypic variance was 52%. Results provide genetic parameters for the application of genetic evaluation for milking speed in Croatian Holstein breed.

milking speed ; Holstein breed ; test-day records ; genetic parameters

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