Relative Palatability to Sheep of Some Browse Species, their In sacco Degradability and In vitro Gas Production Characteristics

Abstract

A study was conducted to estimate the nutritive value of some selected acacia forages using palatability index, in sacco degradability and in vitro gas production characteristics. Ten wethers (mean wt. 18±3.5 kg) were offered Acacia tortilis, Acacia nilotica, Acacia mellifera, Acacia brevispica, Acacia senegal and Leucaena leucocephala (control) using a cafeteria system to determine the species preference by the animals. The acacia species were rich in nitrogen and showed variable palatability pattern. Significant (p<0.05) differences in relative palatability index (RPI) were detected among the species with the following ranking: brevispica > leucaena > mellifera > tortilis > Senegal > nilotica. Acacia nilotica appeared to be of low relative palatability with RPI of 24% and this was attributed to relatively high phenolic concentrations. The DM potential degradability (B) and rate of degradation (c) of the species were significantly (p<0.05) different, ranging from 40.1 to 59.1% and 0.0285 to 0.0794/h respectively. Acacia species had moderate levels of rumen undegradable protein, much higher than that in leucaena. In vitro gas production results indicated the effect of polyphenolic compounds on the fermentation rate, with lower gas production recorded from A. nilotica and tortilis. Based on RPI, A. brevispica and mellifera were superior to the rest and comparable to L. leucocephala. Long-term feeding trials are required with the superior species when used as protein supplements to poor quality diets. (Asian-Aust. J. Anim. Sci. 2001 Vol 14, No. 11 : 1580-1584).