Data reported in the literature indicate that the efficiency of microbial protein production to ruminants vary considerably, i.e. 14-49 g microbial N/kg digestible organic matter apparently fermented in the rumen (ARC, 1984). This variation could be due to the effects of several factors, e.g. different types of feeds, rumen digesta outflow rate. The present experiment was conducted to examine whether there were differences between types of carbohydrate feedstuffs, e.g. ammonia-treated straw, barley and sugar beet pulp, as energy sources for the synthesis of microbial protein in sheep.

Four Blackface x Suffolk wethers (body weight 39-42 kg) fitted with a rumen cannula were used. The animals were housed in metabolic cages and were offered 800 g/day of ammonia-treated straw (control) with or without supplementation with sugar beet pulp or barley at 20%, and 40% on fresh weight basis (SBP20, SBP40, B20 and B40 respectively). A 4 x 5 latin square design was used. The control diet also contained 20 g urea, 20 g casein, 3.4 g Na2SO4 and 10 g mineral & vitamin mixture per kg DM. Its N and ash contents were 25.6 and 74.1 g/kg DM respectively.