Milk Yield Traits, Somatic Cell Score, Milking Time and Age at Calving of Pure Holstein Versus Crossbred Cow

Pure Holstein (HO, n=430), crosses between Swedish Red and HO (SRxHO, n=41), Montbeliarde and HO (MOxHO, n=18), and MO and SRxHO (MOxSH, n=53) were compared for milk, fat and protein yield, fat and protein percentage, somatic cell count (SCC), milking time (MT), and age at first and second calving. A total of 180,933 test-day information for milk yield and MT, and 5,249 for fat and protein percentage and SCC were recorded on first and second parity cows milked in one herd of Cremona province (northern Italy). Somatic cell count and MT were log-transformed to somatic cells score (SCS) and LnMT, respectively, before statistical investigation. Production traits, LnMT and SCS were analyzed through a mixed model that included fixed effects of test-day, parity, days in milk (DIM), genotype and interaction between parity and genotype, and the random effects of cow nested within genotype and residual, whereas the model for age at calving included year and month of calving and genotype as fixed effects, and residual as random. MOxHO and pure HO cows differed only for age at second calving (70 d higher for purebreds; P<0.05). Holsteins produced more milk (+2.86 kg/d; P<0.01) and protein yield (+0.05 kg/d; P<0.05) than SRxHO crossbreds, but lower protein percentage (-0.09%; P<0.01), and age at second calving was 44 d (P<0.01) higher than SRxHO. Also, HO produced more milk and fat than MOxSH cows (+1.61 and +0.08 kg/d, respectively; P<0.05), but lower protein percentage (-0.11%; P<0.001), and calved later, both at first and second calving (+24 and +43 d, respectively; P