Italy: Study sheds light on how heat stress affects cow’s milk

A recent study published in the Journal of Dairy Science reveals the impact of heat stress on the milk microbiota and production parameters in Holstein and Brown Swiss dairy cows. Conducted at a commercial farm in Southern Italy, the study involved exposing 20 cows of each breed to a heat wave by turning off the cooling system for four days. The research team, from universities and the National Research Council of Italy, found that Holstein cows were more negatively affected by heat stress, with changes in milk yield, fat, protein, and casein content, whereas Brown Swiss cows showed only minor changes in lactose levels. Both breeds experienced shifts in saturated, monosaturated, and unsaturated fatty acids. Notably, the milk microbiome of Brown Swiss cows showed more significant changes, with increased abundance of certain bacteria like Streptococcus and Lactococcus, which could increase the risk of mastitis and milk spoilage. This study highlights the thermal tolerance of Brown Swiss cows compared to Holsteins, with ongoing research focusing on how the mammary glands adapt to heat stress and its effects on milk production and quality.