Breeding values prediction for clinical mastitis in Czech Holstein cattle

• Main Author: Ludmila Zavadilová
• Format: Article
• Language: English
• Published: Slovak University of Agriculture in Nitra 2020-12-01
• Series: Acta Fytotechnica et Zootechnica
• Subjects: mastitis; cow; genomic breeding value; multi-trait model; somatic cell score
• Online Access: http://acta.fapz.uniag.sk/journal/index.php/on_line/article/download/718/pdf

This study aims to genetically evaluate clinical mastitis (CM) in Holstein cattle using a two-trait repeatability animal model with the average lactation somatic cell score (LSCS) as an indicator trait of mastitis. The data set included 21,786 Holsteins with 29,110 lactations in 59 herds and with a calving date between 2015 and 2019. CM was considered as an all-or-none trait (values 0 or 1) in the period from calving to 305 days in milk, and the LSCS was obtained by logarithmic transformation of the average of the individual test-day records for somatic cell count over lactation. Heritability of CM was estimated using a single-trait repeatability animal model, whereas the genetic correlation between CM and LSCS was assessed through a two-trait repeatability animal model. Fixed effects included in the analyses were parity-age and herd-year-season, and the random effects were the permanent environment and the animal. The (co)variance matrix was employed in breeding values estimation for both single-trait (only CM) and bivariate models (CM and LSCS) including genomic prediction. Only genotyped sires formed the reference population for the single-step genomic evaluation. The heritability for CM was 0.04 in the single-trait and 0.05 in the two-trait analysis. Genetic correlation between CM and LSCS was 0.80. The employment of the two-trait model had a considerably strong influence on reliability. The reliability increased for cows with records as well as for the genotyped sires. This study indicates that the two-trait analysis of CM and LSCS is feasible and improves the reliability of the estimated breeding values.