Influence of the type of roughage associated with forage cactus Opuntia cochenillifera L. and a lipid source on the milk fatty acids composition of dairy goats.

Modulating the milk fatty acid (FA) profile through dietary strategies is a key approach to enhancing the nutraceutical value of dairy products. This study aimed to elucidate how different basal diets, associated with forage cactus and a lipid source, interact to modulate the milk fat composition of lactating Saanen goats. Twelve multiparous goats, averaging 3.5 years of age and 48.9 ± 7.3 kg body weight, were allocated to a triple 4 × 4 Latin square design. The experimental treatments consisted of corn silage (CS), sorghum silage (SS), grass hay (GH), or sugarcane bagasse (SB), each associated with forage cactus and a concentrate containing full-fat corn germ (FFCG) as the lipid source. The fatty acid profiles of the ingredients in each diet and of the goat milk were determined by gas chromatography. Results revealed a clear metabolic dichotomy driven by the forage source. Silage-based diets (CS and SS) significantly (P < 0.01) increased short- and medium-chain FA, indicating a higher rate of novo synthesis. In contrast, GH and SB diets profoundly altered ruminal biohydrogenation (BH), increasing by 62% the concentrations of vaccenic acid (trans-11 C18:1) and consequently rumenic acid (cis-9, trans-11 CLA) (P < 0.01), without inducing milk fat depression. While GH and SB diets maximized CLA synthesis, CS and SS were more effective in enhancing omega-3 FA transfer, resulting in a more favorable n-6/n-3 ratio (P < 0.01). It is concluded that the forage source is a precision tool to modulate the milk lipid profile, allowing the production of either functional milk rich in CLA or milk with an optimized essential FA composition.