Supplemental Niacin and Fat Effects on Milk Composition of Lactating Holstein Cows

¹ Department of Animal Science, University of California, Davis 95616

Effects of dietary niacin and fat on milk composition, particularly milk N, were evaluated using eight lactating Holstein cows in a replicated 4 x 4 Latin square design, using primiparous and multiparous cow groups. Complete mixed diets contained 2 or 4% added fat and 0 or 125 g niacin per 227 kg of diet. Diets were fed for ad libitum intake, and periods were 21 d. Blood was collected on d 20 from all cows. Multiparous cows were administered with an epinephrine challenge on d 21 followed by serial blood sampling to estimate release of nonesterified fatty acids from adipose tissue.

Milk composition, including milk N fractions, was not different for niacin although lactose was slightly elevated by niacin. Increasing amount of dietary fat slightly increased milk fat percentage and decreased lactose concentration, but other components remained unchanged. Milk yield and DM intake were not affected by either niacin or amount of fat. Niacin and increasing amount of fat decreased the proportion of short- and medium-chain fatty acids (C₄ to C₁₄) of milk fat. Nonesterified fatty acids of plasma were increased by niacin and increasing amount of fat. Total plasma triglycerides increased with amount of fat. Glucose and urea N were not affected by treatments. Plasma nonesterified fatty acids were not affected by treatment in response to epinephrine challenge.

Key Words: niacin • dietary fat • milk composition

Submitted on January 29, 1990
Accepted on June 11, 1990

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