Genetic analysis of milk fatty acids composition of Italian Brown Swiss cows

The aim of this study was to infer variance components and heritabilities for 47 milk fatty acids (FA) (including conjugated linoleic acid) and for unsaturation ratios in the Italian Brown Swiss population. A total of 1,271 cows were sampled once in 85 herds. Milk samples were collected during the evening milking concurrently with the monthly test-day milk recording. Each sample was analyzed for single FA percentages (computed as FA weight as a proportion of total fat weight) by gas chromatography. A Bayesian univariate animal model was implemented via Gibbs sampling. The model accounted for the effect of days in milk, parity, herd and the animal additive genetic effect. Flat prior distributions were assigned to systematic effect and to genetic effect. Heritability (h2) estimates (SD) for unsaturated FA ranged from 0.03 (0.02) for C18:2 trans-15, cis-11 to 0.44 (0.10) for C14:1 cis-9. For the saturated FA the corresponding estimates varied from 0.05 (0.03) for C:22 to 0.43 (0.09) for C:16. Polyunsaturated FA (h2=0.28;SD=0.08) had numerically higher estimates than did monounsaturated (h 2=0.17; SD=0.07) and saturated FA (h2=0.22; SD=0.08). Heritability for index of desaturation (C14:1 cis-9/C14:0 + C14:1 cis-9) and C18:2 cis-9 trans-11 (CLA) were 0.51 (0.11) and 0.18 (0.07), respectively. Results highlight the existence of important and exploitable genetic variations in milk fatty acids composition, which could be used to improve the nutritional properties of milk fat by selective breeding.