Estimation of genetic parameters for somatic cell count in the first three lactations using random regression |
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| Institution: | 1. Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Av. Alemania 01090, 4810101 Temuco, Chile;2. Laboratorio de Parasitología, Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, Spain;3. Departamento de Genética, Facultad de Biología, Universidad de Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, Spain;1. Irish Cattle Breeding Federation, Highfield House, Shinagh, Bandon, P72 X050, Co. Cork, Ireland;2. Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, P61 P302, Co. Cork, Ireland;2. Animal Genomics and Improvement Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350;3. Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada;4. Department of Economic Development, Jobs, Transport and Resources, Bundoora, Victoria 3083, Australia;1. Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy P61 P302, Co. Cork, Ireland;2. Irish Cattle Breeding Federation, Link Road, Carrigrohane, Ballincollig, Co. Cork, P31 D452, Ireland;1. Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Viale dell'' Università 16, 35020 Legnaro PD, Italy;2. Associazione Regionale Allevatori del Piemonte, Via Torre Roa, 13, 12100 Cuneo, Italy;3. Department of Animal Science, Food and Nutrition - DIANA, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy;4. Romeo and Enrica Invernizzi Research Center for Sustainable Dairy Production of the Università Cattolica del Sacro Cuore (CREI), 29122 Piacenza, Italy;5. Italian Association of Breeders (AIA), 00161 Rome, Italy;6. Nutrigenomics and Proteomics Research Center - PRONUTRIGEN, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy |
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| Abstract: | Genetic parameters were estimated for loge somatic cell count (LSCC) for the first three lactations of 31 236 Holstein/Friesian cows with 308 534, 236 277 and 206 729 test day yields in parities 1, 2 and 3, respectively. An animal random regression model was employed in the analyses using Gibbs sampling with each parity regarded as different traits. Linear and quadratic functions were fitted for the animal and permanent environmental effects respectively, using orthogonal polynomials. Daily heritabilities increased with days in milk (DIM) and averaged about 0.07 in all three parities. This increase in heritabilities with DIM was due to an increase in genetic variance and decreases in both permanent and residual environmental variances with DIM. Environmental effects have a large influence on LSCC in early lactation in all three parities. Within lactation, genetic correlations were highest between adjacent DIM but decreased as DIM got further apart. However, this decrease was slowest in parity one and greatest in parity three. The lowest correlation within lactation was 0.10 between DIM 7 and 305 in parity 3. Across lactations, genetic correlations were highest between parities 2 and 3, intermediate between 1 and 3, and lowest between 1 and 2. The genetic correlations computed for completed lactations were 0.69, 0.79 and 0.98 between parities 1 and 2, 1 and 3, and 2 and 3, respectively. Corresponding phenotypic correlations between parities were 0.38, 0.31 and 0.52, respectively. A test day model, accounting for these variations in heritabilities and genetic correlations, should result in a more accurate evaluation. |
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