Effects of forage neutral detergent fiber and yeast culture on performance of cows during early lactation.

Sixty Holstein cows were assigned to two treatments at 21 d before calving and were group-fed a prepartum diet with or without yeast culture. After parturition, cows were individually fed one of five treatments for 140 d: 1) 21% forage neutral detergent fiber (NDF) without yeast culture, 2) 21% forage NDF with yeast culture, 3) 17% forage NDF without yeast culture, 4) 17% forage NDF with yeast culture, and 5) 25% forage NDF with yeast culture for 30 d and then switched to diet 4 for 110 d. Cows fed yeast culture prepartum were also fed yeast culture postpartum (60 g/d). A quadratic increase to 25, 21, and 17% forage NDF occurred during the first 30 d in milk (DIM) for dry matter intake, milk yield, and milk protein yield. No differences were observed for yeast culture or interaction of yeast culture and forage NDF for the first 30 DIM. Feeding 17 versus 21% forage NDF increased milk protein percentage and tended to increase dry matter intake as a percentage of body weight from 31 to 140 DIM. During this period, yeast culture tended to increase milk fat percentage and appeared to have positive effects on dry matter intake, milk yield, and milk fat yield when supplemented to diets with 21% forage NDF but not with 17% forage NDF. Feeding 17% forage NDF may be too low for the first 30 DIM but may improve animal performance after 30 DIM compared to 21% forage NDF.