Abstract:
The aim of this study was to compare intake and partial digestibility of organic matter (OM) and nitrogen (N) of two ensiled tropical grass species, P. maximum and D. eriantha, made either at the boot or full bloom stage of growth. Intake and digestibility were determined by the double marker technique where Yb and Cr were infused continuously into the rumen with a peristaltic pump. Except for OM disappearance in the digestive tract, neither species nor stage of harvesting had an effect on intake, digesta flow and OM disappearance within the rumen and small intestine. For P. maximum silage, N intake (g/d) was higher at the full bloom than at the boot stage. Total abomasum N flow (g/d), non-ammonia nitrogen (NAN) flow (g/d), NAN flow per N intake and NAN disappearance as % of N intake in the gastrointestinal tract (GIT) were higher for sheep fed on D. eriantha than P. maximum silage made at full bloom. In D. eriantha silage NAN disappearance was higher for silage at full bloom than D. eriantha silage at boot stage. The true N-digested (%), however, did not differ significantly between the species or stage of maturity. In terms of NAN disappearance in the lower GIT it is evident that silage made from D. eriantha at the full bloom stage is superior to silage made at the boot stage, as well as to silage made from P. maximum.
