Studies on the ruminal concentration of total volatile fatty acids (VFA's) and their molar proportions in African cattle, sheep and goats

Abstract

Few data comparing the utilization of feeds by African cattle, sheep and goats are available. The experiment, involving five adult animals with permanent rumen cannulae, supplies comparative data on fermentative digestion in these ruminants under tropical conditions. Two Red Sokoto (Maradi) goats, two West African dwarf sheep, and one White Fulani (Zebu) steer were first maintained on a basal ration of freshly chopped Cynodon nlemfuensis and Centrosema pubescens for 21 days, followed by the forage plus groundnut cake or urea concentrate supplements at 0, 10, 17 and 24% protein levels. Supplementation of the basal rations with the concentrates brought about increasing levels of total VFA's in the animals, tending to be higher in the steer than in the goats or sheep, with no appreciable differences for the individual VFA's and ruminal pH. It also resulted in a significant lowering of the acetic acid levels ( P<0.05) with a corresponding increase of the propionic acid concentration in the rumen, giving the lowest molar % of acetic acid and the highest molar % of propionic acid with the 17% crude protein concentrate. While the increasing levels of the proteins or urea in the concentrate resulted in significant increases in the iso-butyric acid concentration ( P<0.05) differences in the concentration of n-butyric acid were not significant ( P>0.05). However, the basal ration produced neither iso-butyric acid nor n-valeric acid in the rumens of these animals. It was a noteworthy observation that n-valeric acid production (about 3 percent) occurred only with the 24 percent groundnut cake protein.