Effects of supplementation with yeast culture and enzymatically hydrolyzed yeast on performance of early lactation dairy cattle.

One hundred fifty multiparous cows were balanced to 1 of 3 treatments (2 pens/trt) according to previous lactation 305-d mature equivalent yield to evaluate supplementation with yeast culture (YC; A-Max, Vi-COR, Mason, IA) and YC plus enzymatically hydrolyzed yeast (YC+EHY; Celmanax, Vi-COR) on production performance in dairy cattle. Cows entered pens at calving and remained through 14 wk postpartum. Treatment assignment to pens was random throughout the barn. Pens were identical in layout and each contained an exit alley to eliminate feed and animal mixing. The 3 treatments were control: nonsupplemented; YC: control diet with YC (56 g/d); and YC+EHY: control diet plus YC and EHY (28 g/d). Mean pen dry matter intake was similar across treatments. Cows supplemented with YC and YC+EHY produced more milk, fat-corrected milk, and energy-corrected milk than control cows (1.4 and 1.6, 1.6 and 1.8, 1.7 and 1.9 kg, respectively). Treatments YC and YC+EHY did not differ. Milk fat and lactose percentages were not affected by treatment. Milk protein percentage was higher for cows supplemented with YC+EHY than for those on YC and control treatments (2.98, 2.93, and 2.91%, respectively) with control and YC-supplemented cows not being different from each other. Differences in fat and protein yields were primarily reflective of milk yield. Treatment had no effect on milk urea nitrogen. No differences in the incidence of metabolic health were observed; however, cases of clinical mastitis for YC+EHY were less than half those for control and YC during wk 8 to 14 on trial. Somatic cell count was higher for cows fed control and YC diets compared with YC+EHY, primarily during wk 8 to 14 on trial. Supplementation of early lactation cows with YC improved milk production performance; furthermore, EHY supplementation improved milk protein percentage and mammary gland health.