The effect of urea on the absorption of volatile fatty acids from the rumen of sheep fed on oat straw

Abstract

The effect of a urea supplement on the utilization of a diet of poor quality oat straw plus minerals, fed to sheep, was investigated. The supplement of urea was responsible for a highly significant (P < 0.01) increase in dry matter and energy intake and a highly significant ( P < 0.01) decrease in body weight loss.

There was a significant (P < 0.05) increase in nitrogen balance and in the rate of passage of food residues through the alimentary tract. A tendency for the digestibility of dry matter, energy, crude fibre, and cellulose to be higher when the urea supplement was given was not significant. There was a significant (P < 0.05) increase in the VFA absorbed from the rumen reflecting the increase in intake, but there were no differences between diets in the contributions of acetic, propionic, and butyric acids to VFA absorption. The mean values obtained for the proportion of the digested energy accounted for by the VFA on the straw plus urea diet and the straw diet (with the standard error of the mean) were 31.4 (± 2.5)% and 38.1 (± 5.6)% respectively.