Genetic parameters for milk fatty acid profiles in Gir and Guzerá cows using a Bayesian approach

Studies with taurine breeds indicate that genetic selection can improve the fatty acid (FA) composition of bovine milk. This study aimed to estimate genetic parameters for FA concentrations and unsaturation indexes in milk fat from Zebu cows and evaluate their potential as selection criteria to enhance milk fat nutritional quality. Milk samples from 299 Gir and 266 Guzerá cows across 22 herds were analyzed by gas chromatography. Fourteen individual FAs, 11 FA groups, four nutritional quality indexes, and five unsaturation indexes were selected. Tri-trait Bayesian models were used to estimate (co)variance components, using 305-day milk yield and fat yield as anchor traits. The models included fixed effects such as contemporary group, age at calving, diet category, age class at sampling, and days in milk. Most individual FAs were present at concentrations < 4 g/100 g of total FA, with palmitic acid being the most abundant, followed by oleic acid, stearic acid, and myristic acid. Heritability estimates ranged from 0.28 to 0.63 for individual FAs, 0.32 to 0.66 for FA groups, and 0.38 to 0.57 for unsaturation indexes in the Gir breed, and from 0.24 to 0.75, 0.26 to 0.65, and 0.50 to 0.68 in the Guzerá breed, respectively. Genetic correlations were generally moderate to high, with long-chain FAs negatively correlated with short- and medium-chain FAs. These findings support the feasibility of selecting Gir and Guzerá cows to genetically improve milk FA profiles and increase the proportion of health-promoting FAs in milk fat.