Fatty acids milk composition in Italian Simmental and Italian Holstein cows

Increasing importance is given to healthy diets and to satisfy this demand, the benchmark of milk quality now includes also the specific composition of the lipid and protein fractions in milk. Milk fat has been criticized because of its higher concentration of saturated fatty acids (SFA) and low concentrations of monounsaturated (MUFA) and poly- unsaturated (PUFA), but fatty acids (FA) profile can be improved via genetic selection, which can provide a more permanent solution compared with managementrelated approaches. The aim of this work is to estimate the correlations among groups of milk FA, namely SFA, unsaturated (UFA), MUFA and PUFA, and EBVs (kg of protein EBVp, kg of fat EBVf) in Italian Simmental (IS) and Italian Holstein (IH) cattle. Milk sampling was conducted in 6 commercial farms of IS and 4commercial farms of IH. Cows had free access to water and a ad libitum total mixed ration offered twice a day. The day of official milk recording, 100 mL of milk individual samples were collected and split in two 50 mL aliquots, one used for the determination of protein, fat, lactose and for somatic cell count (SCC) and the second frozen at -20°C within 2 hours for fatty acid analyses. Before statistical analysis, animals were classified for parity with ordinal value of 1 for first calving, 2 for second calving and 3 for cows with more than 2 calving. Analysis was performed with a mixed model, with fixed effects of Breed and Parity and random effect of Farm and the linear relationships with DIM and with EBVs within breeds. Results evidenced a significant correlation between SFA, UFA, PUFA, MUFA with EBVp and EBVf in both breeds. Relevant to highlight is the ratio rumenic/(vacenic+rumenic), resulted to be statistically significant considering breeds as well as EBVp and EBVf. This may be due to a divergent selection for the gene involved in vaccenic/rumenic methabolism in the two breeds while the significant association with EBVf and EBVp suggests the existence of a genetic variability of the trait within breeds. Daily CH4 emission (g/kg of FPCM), estimated on the basis of fatty acid profile, was also correlated with EBVf and EBVp. Although further investigations are required, these traits can be considered in breeding programs for the next generation dairy cows.