Impact Of Us Brown Swiss Genetics On Milk Quality From Low-Input Herds In Switzerland: Interactions With Season

This study aimed to investigate the effect of, and interactions between, US Brown Swiss genetics and season on milk yield, basic composition and fatty acid profiles, from cows on low-input farms in Switzerland. Milk samples (n=1,976) were collected from 1,220 crossbreed cows with differing proportions of BS, Braunvieh and Original Braunvieh genetics on 40 farms during winter-indoor and summer-grazing seasons. Cows with more Brown Swiss genetics produced more milk in winter but not in summer, possibly because of underfeeding high-yielding cows on low-input pasture-based diets. Cows with more Original Braunvieh genetics produced milk with higher concentrations of (i) nutritionally desirable <em>trans</em>-9 palmitoleic, eicosapentaenoic and docosapentaenoic acids, throughout the year, and (ii) vaccenic and α-linolenic acids, total omega-3 fatty acids concentrations and a higher omega-3/omega-6 ratio during the summer-grazing period only. This suggests that overall milk quality could be improved by re-focusing breeding strategies on the cows’ ability to respond to local dietary environments and seasonal changes in feeding regimes.