Genetic Parameters of Bovine Milk Fatty Acid Profile, Yield, Composition, Total and Differential Somatic Cell Count

Abstract

The growing interest of consumers for milk and dairy products of high nutritional value has pushed researchers to evaluate the feasibility of including fatty acids (FA) in selection programs to modify milk fat profile and improve its nutritional quality. Therefore, the aim of this study was to estimate genetic parameters of FA profile predicted by mid-infrared spectroscopy, milk yield, composition, and total and differential somatic cell count. Edited data included 35,331 test-day records of 25,407 Italian Holstein cows from 652 herds. Variance components and heritability were estimated using single-trait repeatability animal models, whereas bivariate repeatability animal models were used to estimate genetic and phenotypic correlations between traits, including the fixed effects of stage of lactation, parity, and herd-test-date, and the random effects of additive genetic animal, cow permanent environment and the residual. Heritabilities and genetic correlations obtained in the present study reflected both the origins of FA (extracted from the blood or synthesized de novo by the mammary gland) and their grouping according to saturation or chain length. In addition, correlations among FA groups were in line with correlation among individual FA. Moderate negative genetic correlations between FA and milk yield and moderate to strong positive correlations with fat, protein, and casein percentages suggest that actual selection programs are currently affecting all FA groups, not only the desired ones (e.g., polyunsaturated FA). The absence of association with differential somatic cell count and the weak association with somatic cell score indicate that selection on FA profile would not affect selection on resistance to mastitis and vice versa. In conclusion, our findings suggest that genetic selection on FA content is feasible, as FA are variable and moderately heritable. Nevertheless, in the light of correlations with other milk traits estimated in this study, a clear breeding goal should first be established.

Associations among Farm, Breed, Lactation Stage and Parity, Gene Polymorphisms and the Fatty Acid Profile of Milk from Holstein, Simmental and Their Crosses

“…Except for genetic correlations between group FAs with somatic cell scores, other correlations were significant. A similarly focused study [ 4 ] found the same tendencies in genetic correlations. Negative correlations with milk and protein yield and positive correlations with the percentage of fat, protein and casein.…”

“…Authors calculated with results of 885,249 repeated test-day milk records. Heritability values may also reflect the origins of FA (performed or synthesized de novo) and their grouping according to saturation or chain length [ 4 ].…”

“…Such genetic parameters indicate that genetic selection could be used to change the composition of milk fat [ 2 , 3 ]. Moderate correlations between FA and basic indicators of milk performance suggest that the selection program could affect all FA groups; however, not only the desired ones [ 4 ].…”

Polymorphisms of the IL-17A Gene Influence Milk Production Traits and Somatic Cell Score in Chinese Holstein Cows

“…Some critical features directly impact the milk yield and production capacity [ 10 ]. There is a strong correlation in various production metrics, such as fat content and milk yield, protein content, milk urea nitrogen, and somatic cell count [ 11 , 12 ].…”

A Practical Application of Genomic Predictions for Mastitis Resistance in Italian Holstein Heifers

“…Therefore, a useful proxy to assess mastitis is milk somatic cell count (SCC) and its log transformation somatic cell score (SCS): an index that evaluates the inflammatory status of the mammary gland, which has been widely used to monitor milk quality and udder health [ 16 ], and to select cows with a reduced susceptibility to mastitis [ 17 ]. Furthermore, heritability of SCS was assessed to be low-to-moderate (e.g., 0.05 to 0.10) [ 17 , 18 ], thus suggesting the possibility of performing genetic selection [ 19 ]. More specifically, genomic selection could be of use when dealing with low-to-moderate heritability traits [ 20 ].…”