Wet brewers grains for lactating dairy cows during hot, humid weather.

Twenty lactating Jersey cows were offered diets containing 0, 15, or 30% wet brewers grains or 30% wet brewers grains plus liquid brewers' yeast during hot, humid weather. The DMI was not different, even though diets with 30% wet brewers grains contained only 35.5% DM and approximately 50 versus 36.8% NDF for the control diet. Yields of milk and FCM did not differ for cows offered the control diet versus wet brewers grains or diets with 15 versus 30% wet brewers grains, but milk yield for diets with 30% wet brewers grains was greater with added liquid brewers' yeast than without it. Milk fat percentage was not different, but milk protein percentage was lower, for diets with wet brewers grains than for controls and for 30% wet brewers grains than for 15% wet brewers grains. Serum urea N was lower for control cows than for cows receiving the diets with wet brewers grains. Feed cost per cow was lower for wet brewers grains versus the control diet, and income over feed cost was greater for diets with 30 versus 15% wet brewers grains. Large quantities of wet brewers grains can be added to the diet during hot weather without depressing DMI.