Rumen degradation characteristics of two tropical forages supplemented with monensin in the rumen of N’dama Steer

Abstract

Rumen degradation characteristics of Panicum maximum and Gmelina arborea forages in response to monensin supplementation were studied in a 2 x 4 factorial experiment using an N’dama fistulated steer. Monensin had no significant effect (P>0.05) on the soluble fraction ‘a’ of nutrients but showed reductions (P<0.05) in the degradable fractions ‘b’ of dry matter, crude protein, neutral detergent fibre and acid detergent fibre at 30 and 45 mg/kg DM supplementation levels relative to the control. These reductions were within the range of 45.76 - 49.52, 37.88 - 43.57, 44.60 - 45.31 and 45.18 - 46.85% for DM, CP, NDF and ADF, respectively. The potential degradation ‘p’ of DM, NDF, and ADF reduced (P<0.05) at 30 and 45 mg/kg DM while ‘p’ for CP reduced at 45 mg/kg DM. Forage type had significant effect (P<0.05) on nutrient degradation with Panicum maximum having lower nutrient degradation characteristics values than those of Gmelina arborea. While monensin reduced nutrient degradation from Panicum maximum at 30 and 45 mg/kg DM, reduction in nutrients degradation from Gmelina arborea was observed only at 45 mg/kg DM. Comparatively, at similar levels of 15, 30 and 45 mg of monensin/kg DM, Panicum maximum had lower (P<0.05) degradation values to those observed for Gmelina arborea. The reduction effect of monensin on nutrient degradation from both forages suggests an inhibition of microbial digestion. This could increase rumen fill, reduce ruminal outflow rate and possibly increase the proportion of un-degradable proteins leaving the rumen for the lower tract. The particular level of monensin supplementation at which such reductions would occur depends on forage type.

Keyords: Gmelina arborea, Panicum maximum, Nutrient degradation, Fistulation, N’dama steer.