RUMINAL FERMENTATION AND TANNINS BIOACTIVITY OF SOME BROWSES USING A SEMI-AUTOMATED GAS PRODUCTION TECHNIQUE

Abstract

The nutritive value, tannins bioactivity and methane production of some tropical plants e.g. Acacia (Acacia saligna), Leucaena (Leucaena leucocephala), Atriplex (Atriplex caseneace), Eucalyptus (Eucalytus globules), and Alfalafa (Medicago sativa) hay were evaluated by chemical composition and gasp production (GP) technique in vitro. Chemical analysis indicated that crude protein content was ranged from 95.4 to 204.0 g kg-1DM for eucalyptus and leucaena, respectively. The leucaena and alfalfa had the highest neutral detergent fibre (NDF) content (543.1 and 546.7g kg-1DM), respectively. Atriplex had the lowest content (173.8 g kg-1DM) of acid detergent fibre (ADF) and acid detergent lignin (ADL, 85.89 g kg-1DM). Alfalfa, atriplex and eucalyptus had negligible condensed tannins (CT) content (0.2, 0.3, 4.9 eq-g leucocyanidin kg-1DM), while acacia and leucaena had the highest CT (61.4 and 32.5 eq-g leucocyanidin kg-1DM). The acacia and leucaena produced less GP in the absence of PEG.  Inclusion of PEG in fermentation of tropical browses resulted in a significant increase of GP (28.1 and 87.4 1%) particularly the plants rich in condensed tannins. The methane production was decreased significantly (P<0.05) by 88, 89 and 90.9 % in lucaena, acacia and eucalyptus samples, respectively in comparison to alfalfa. The ranking order of the browse species on the basis of their potential degradability of in vitro dry and organic matter degradability (DMD, OMD) was atriplex > alfalfa > acacia > eucalyptus > leucaena. Partitioning factor (PF) values were differed significantly (P<0.05) among plants. It is concluded that the four evaluated plants represent an important fodder reserve for livestock in harsh conditions according to the chemical composition, GP and fermentation pattern.