Seasonal in vitro gas production parameters of three multi - Purpose tree species in Abeokuta, Nigeria

Leaves from three indigenous multipurpose tree species (MPTS) namely Moringa oleifera, Millettia griffoniana and Pterocarpus santalinoides were randomly collected in July, October and December 2004, to represent mid wet, late wet and early dry season respectively. The leaves were analyzed to estimate the nutrient composition and in vitro gas production over 3, 6, 9, 12, 15, 18, 21, 24, 48, 72 and 96h post incubation. The gas volumes recorded at these incubation times were fitted to the model P = b (1 - e-ct). Influences of chemical constituents on gas production were investigated. Cumulative gas released at 96h was 35.8ml/200mg DM for Millettia griffoniana whereas Moringa oleifera and Pterocarpus santalinoides recorded 32.2 and 28.7ml/200mg DM respectively. These values were not significant (P>0.05). The highest volume originating from the (b) fraction was recorded for Millettia griffoniana (44.9ml/200mg DM) during the late wet season while the lowest value for this fraction was recorded for Pterocarpus santalinoides (22.5ml/200mg DM) (P>0.05) during the same season. The highest fractional rate of gas production (c) was recorded for Pterocarpus santalinoides (0.058ml/h) whereas Pterocarpus santalinoides and Millettia griffoniana both recorded the lowest fractional rate of production of 0.024ml/h during the mid wet and late wet season respectively. The correlation coefficients between in vitro gas production and the chemical constituents of the forages were generally negative. Significant correlations were observed in the ADF and ash contents of Moringa oleifera and Pterocarpus santalinoides. The in vitro gas production and the fermentation parameters indicated the presence of potentially degradable nutrients in the MPTS evaluated. This underscores their importance as sources of nutrients for ruminant animals especially during the dry season. It is concluded that the in vitro gas production technique is a potential way of evaluating the nutritional quality of forages consumed by ruminant animals and also invaluable in predicting nutritive value of some of our under - utilized indigenous browse plants.