The objective of this study was to estimate phenotypic and genetic parameters for milk traits including lactose and somatic cell score (SCS) over lactation of Italian Jersey dairy cattle. A total of 38,831 test-day records from 1,902 cows were collected from 2005 to 2016 in 20 dairy herds located in Italy. Days in milk were between 5 and 480 and thirteen classes of days in milk were defined. Analysis of variance was performed with a mixed linear model that included the fixed effects of herd-test day (n = 920), parity (5 classes), stage of lactation, calving season and interaction between parity and stage of lactation, and the random effects of animal and cow permanent environment. Heritabilities were estimated using a single-trait repeatability animal model, and genetic correlations were assessed through bivariate analyses. Mean milk yield was 18.76 kg/d, containing 5.29% fat, 4.09% protein, 3.20% casein, 4.80% lactose and 3.02 units of SCS. During lactation solids content and SCS increased, while solids yield decreased. Heritability estimates were 0.14, 0.21, 0.26, 0.24, 0.20 and 0.10 for milk yield, fat, protein, casein, lactose percentage and SCS, respectively. Genetic correlations between SCS and solids yield were negative, with the strongest estimate with lactose percentage (-0.30). Results of the present study emphasize quality of milk yield and composition of Italian Jersey cows and the possibility to develop new selective strategies for this breed. Keywords: genetic parameter, milk yield, milk composition, somatic cell count, Jersey breed
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology & Species - Bovine (dairy) 2, , 686, 2018
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