Effect of poly ethylene glycol addition on Nutritive Value and Gas production parameters of four browsing Trees.

Abstract

Nutritive value of four browsing trees (Acacia.torrtlis , Ziziphus.spinachristi , Acacia.mellifera and Acacia.seyal ) leaves and pods were evaluated by estimating chemical composition and in vitro gas production techniques.The chemical composition for both leaves and pods were significantly different (p<0.01 ) among the species . Crude protein (CP) contents ranged from 16.0 to 24.1 %. Acid detergent fibre (ADF) and neutral detergent fibre (NDF) contents varied within species in the range 18.5- 43.8 % and 36.1 - 72.3% respectively . Total condensed tannin (TCT) contents ranged from 0.5- 6.2%. TCT were negatively correlated with fraction (b) and (a +b) whereas ADF were negatively correlated with most of the estimated parameters . The gas production parameters significantly varied among the species . There were also significant differences in terms of cumulative gas production , invitro organic matter digestibility (IOMD) and calculated metabolizable energy (ME). The addition of poly Ethylene Glycol (PEG) significantly increased (p<0.01 ) the gas production from both soluble and insoluble fraction (a) and (b) , invitro organic matter digestibility (IOMD) and metabolizable energy (ME) . The IOMD values of leaves and pods without PEG ranged from viii 39.7to 64.5 % and with PEG ranged from 37.9 to 80.0 %. While the ME content without PEG ranged from 5.9 to 10.6 MJ kg/DM and the ME content with PEG ranged from 5.7 to 13 MJ kg/DM The best improvement in gas production, invitro organic matter digestibility (IVOMD) and metabolizable energy (ME) were observed with 50% PEG w/w. Generally this improvement indicate the negative effect of tannins on digestibility.