EFFECTS OF NONFIBER CARBOHYDRATE AND NIACIN ON PERIPARTURIENT METABOLIC STATUS AND LACTATION OF DAIRY-COWS

Fifty Holstein cows and 25 Holstein heifers were used in a randomized complete block design. Treatments were a standard nonfiber carbohydrat e diet beginning at 19 d prepartum, a high nonfiber carbohydrate diet beginning at 19 d prepartum, a standard nonfiber carbohydrate diet plu s niacin (12 g/d) beginning at 19 d prepartum, a high nonfiber carbohy drate diet plus niacin beginning at 19 d prepartum, and a standard non fiber carbohydrate diet beginning at 19 d prepartum plus niacin beginn ing at 14 d postpartum. Treatments were applied through 40 wk postpart um. Niacin did not significantly affect production parameters or blood and Liver metabolites. Prepartum intakes of dry matter and energy and energy balance were greater for cows and heifers fed the high nonfibe r carbohydrate diets. Plasma glucose concentrations tended to be signi ficantly higher, and nonesterified fatty acids and beta-hydroxybutyrat e concentrations were significantly lower, when animals were fed diets that were high in nonfiber carbohydrates. Diets containing high nonfi ber carbohydrates increased concentrations of liver glycogen and tende d to reduce concentrations of liver triglyceride. Milk production tend ed to be higher, milk fat percentage tended to be lower, and milk prot ein percentage and production were significantly greater when diets th at were high in nonfiber carbohydrates were fed. An increase in dietar y nonfiber carbohydrates improved the metabolic parameters during the transition period and improved lactation performance.