Genetic parameters for milk fatty acids, milk yield and quality traits of a Holstein cattle population reared under tropical conditions

Authors: PETRINI, JULIANA - Universidade De Sao Paulo; IUNG, LAIZA H - Universidade De Sao Paulo; MOREIRA, JOSÉ MAURO - Universidade De Sao Paulo; SALVIAN, M - Universidade De Sao Paulo; PERTILLE, FABIO - Universidade De Sao Paulo; ROVADOSCKI, GREGORI - Universidade De Sao Paulo; CASSOLI, LAERTE - Universidade De Sao Paulo; COUTINHO, LUIZ - Universidade De Sao Paulo; MACHADO, PAULO - Universidade De Sao Paulo; Wiggans, George; MOURAO, GERSON - Universidade De Sao Paulo

Submitted to: Journal of Animal Breeding and Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2016
Publication Date: 9/12/2016
Citation: Petrini, J., Iung, L.S., Moreira, J., Salvian, M., Pertille, F., Rovadoscki, G.A., Cassoli, L.D., Coutinho, L.L., Machado, P.F., Wiggans, G.R., Mourao, G.B. 2016. Genetic parameters for milk fatty acids, milk yield and quality traits of a Holstein cattle population reared under tropical conditions. Journal of Animal Breeding and Genetics. 133(5):384-395.

Interpretive Summary: Information about genetic parameters is essential for the design of animal breeding programs and for the prediction of selection response. Although these values have been reported for several important traits in dairy cattle production, genetic parameters are populationspecific, and selection decisions will be only correct if they were based on the information from the actual population under selection. In addition, studies involving populations under tropical and subtropical conditions are rare. Therefore, genetic parameters for milk production traits, including fatty acid composition, were estimated using pedigree and genomic information from a Holstein cattle population reared under tropical conditions in Brazil. Lactose and protein content in milk were highly heritable (around 30%), and percentages of fat, saturated fatty acids, and palmitic acid in milk were moderately heritable (19 to 26%); those heritabilities revealed the possibility of improving milk quality by using selection. An antagonistic relationship was found between milk yield and milk components as well as between milk fat content and total saturated fatty acids; those traits should be genetically evaluated simultaneously with consideration given to their economic relevance as well as their phenotypic and genetic relationships. The results highlight the importance of using genetic parameters estimated in the population under evaluation for selection decisions.

Technical Abstract: Information about genetic parameters is essential for selection decisions and genetic evaluation. Those estimates are population specific, but few studies are available for dairy cattle populations reared under tropical and subtropical conditions. Heritability and genetic correlations for milk yield and quality traits were estimated using pedigree and genomic information from a Holstein population maintained in a tropical environment. Phenotypic records (36,457) of 4,203 cows as well as genotypes for 57,368 single nucleotide polymorphisms from 755 of those cows were used. Covariance components were estimated using the restricted maximum likelihood method under a mixed animal model with either a pedigree-based relationship matrix or a combined pedigree-genomic matrix. High heritabilities (around 0.30) were estimated for lactose and protein content in milk, whereas moderate values (between 0.19 and 0.26) were obtained for percentages of fat, saturated fatty acids, and palmitic acid in milk. Genetic correlations ranged from -0.38 to -0.13 between milk yield and composition traits. The smaller estimates (compared with those from similar studies) may be the result of poor environmental conditions, which may reduce genetic variability. These results highlight the importance of using genetic parameters estimated in the population under evaluation for selection decisions.