Ruminal Acid Production in Lambs Fed Pelleted Diets Containing Different Levels of Concentrates

Abstract

Two trials were conducted to determine the effects of pelleting and level of concentrates on rumen pH and volatile fatty acid production in lambs. Diets composed of all roughage or containing 20, 40, 60 and 80% concentrates were studied. Feeding of diets containing 40% or more concentrates consistently lowered the concentration of acids and pH in the rumen. Adding concentrates to the diets lowered the molar proportion of acetate and increased the proportion of propionate, butyrate and branched-chain acids. Pelleting the diet containing 60% concentrates decreased the level of acetate and increased the level of propionate. Higher levels of rumen acids were associated with pelleting the roughage portion of diets containing 20 or 80% concentrates. Pelleting the concentrate portion of a high-concentrate diet narrowed the acetate to propionate ratio to a greater extent than pelleting the complete diet. In vitro studies indicated that rumen microorganisms readily distinguished between levels of concentrate or soluble carbohydrate but could not detect differences due to the pelleting process. Pelleting did not influence the solubility of nitrogen in alfalfa hay or diet containing 20% concentrate. Pelleting tended to increase the solubility of nitrogen in high-concentrate feeds. Copyright © 1967. American Society of Animal Science . Copyright 1967 by American Society of Animal Science