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 trans-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.

本研究旨在探究瑞士低投入牧场奶牛的美国布朗瑞士（US Brown Swiss）遗传背景与季节对其产奶量、基础乳成分及脂肪酸谱的影响及其交互作用。研究于冬季舍饲期与夏季放牧季，在40个牧场中采集了1220头携带不同比例布朗瑞士、瑞士褐牛（Braunvieh）及原种瑞士褐牛（Original Braunvieh）血统的杂交奶牛的乳样，共计1976份。携带布朗瑞士血统比例更高的奶牛在冬季产奶量更高，但夏季无此优势，这一现象可能源于低投入牧场的草基日粮无法满足高产奶牛的营养需求。携带原种瑞士褐牛血统比例更高的奶牛，其乳中全年均维持较高浓度的（i）营养学上有益的反式-9-棕榈油酸（trans-9 palmitoleic）、二十碳五烯酸（eicosapentaenoic acid）与二十二碳五烯酸（docosapentaenoic acid）；且仅在夏季放牧季，其乳中反式-11-十八碳烯酸（vaccenic acid）、α-亚麻酸（α-linolenic acid）、总ω-3脂肪酸（total omega-3 fatty acids）浓度及ω-3/ω-6比值均更高。本研究结果提示，将育种策略重新聚焦于奶牛适应本土日粮环境与饲喂制度季节变化的能力，可有效提升整体乳品质。