Intake, digestibility and milk production and composition of dairy cows fed different levels of Yerba Mate in the diet

Abstract

Eight multiparous lactating Holstein cows fitted with rumen cannulas and averaging 84±18 (mean±SD) days in milk and 598±55kg of body weight were assigned to a replicated 4×4 Latin square design to determine the effects of feeding Yerba Mate (YM) on intake, digestibility, milk production, milk composition, and milk concentration of antioxidants when cows were fed a corn silage-based diet containing ground canola seed. The treatments fed for ad libitum intake were: a total mixed ration not supplemented (0g/d), or supplemented (250, 500 or 750g/d) with dried leaves of YM. Experimental periods consisted of 14 d of diet adaptation and 7 d of data collection and sampling. Increased supplementation of the diet from 0 to 750g/d YM had no effect on milk production or yields of protein and fat, and decreased milk yields of lactose and total solids and milk urea N concentration. Digestibility of dry matter, protein and neutral detergent fiber was similar among diets and ether extract digestibility decreased with the level of YM supplementation. Concentrations of total polyphenols and production of conjugated diene hydroperoxides and thiobarbituric acid reactive substances in milk were similar among diets. The reducing power in milk increased with the inclusion level of YM in the diet, thus suggesting that antioxidant activity of milk can be enhanced with this feeding strategy although it was clearly insufficient to overcome the negative effects on milk fat synthesis probably caused by the high levels of fat added to diets as ground canola seed.