EFFECT OF SUPPLEMENTATION ON DIGESTIBILITY AND NITROGEN BALANCE BY DORPER AND LOCAL MALAWI SHEEP FED MAIZE STOVER
AbstractTen Dorper (16.0 to 37.0 kg) and 10 local (15.0 to 28.5kg) rams were fed maize stover offered at 2 times the requirement for maintenance with urea lick (UL) or bean shells (BS) or poultry manure (PM). Bean shells and PM treatments included urea solution to provide 1.2% N in the diet. In this study the sheep consumed leaves and rejected all stems. Intake of total dry matter and neutral detergent fibre (NDF) was highest (P<0.001) with PM supplementation while the intake of nitrogen was higher (P<0.001) in both BS and PM treatments. Digestibility was highest (P<0.001) for sheep supplemented with BS. Higher N intake of the stover diet increased digestibility of dry matter, NDF and N as well as intake of dry matter owing to the stimulation of microbial activity. However, digestibility decreased with higher NDF intake when PM was used as a supplement. Liveweight gain was highest (P<0.001) for sheep supplemented with PM (145 g/day) reflecting high intake. Sheep supplemented with BS lost weight (-37 g/day) due to several factors, one of which was inefficient utilization of absorbed N which was reflected in high urinary N excretion by the sheep. Nitrogen balance was positive for all treatments and nitrogen retention increased (P<0.001) with high N intake. Breeds did not differ in voluntary intake of dry matter, NDF and N. Dorper sheep (D) had higher digestibility of DM (P<0.001), NDF (P<0.001) and N (P<0.05), higher N retention (P<0.001) and gained more (P<0.001) weight than local sheep (L). With BS and PM supplementation, total tract mean retention time (MRT) was longer in Dorper than local sheep. It was concluded that for sheep fed low quality maize stover, voluntary intake, digestibility, N retention and liveweight gain increased by offering greater amounts of stover with a high N intake and PM could be used as a cheap N supplement. Differences in digestibility due to MRT suggest that the Dorper breed could be a valuable resource for sheep production even in areas where low quality maize stover limits the use of European breeds.
(UNISWA J Agric: 2000 9: 34-40)