Intake, digestion and microbial protein synthesis in sheep on hay supplemented with prickly pear cactus [Opuntia ficus-indica (L.) Mill.] with or without groundnut meal

Prickly pear cactus [Opuntia ficus-indica (L.) Mill.] and roughage (Cenchrus ciliaris)-based diets with (OCG) or without (OC) an organic N source supplement (50 g groundnut meal) were compared to a roughage plus 200 g concentrate (CC)-supplemented diet. Intake, nutrient utilization, rumen fermentation, excretion of urinary purine derivatives and microbial N supply in Malpura hoggets were assessed. Opuntia cladodes contained DM 218 g/kg, CP 126 g/kg, NDF 466 g/kg and ash 172 g/kg of DM. Dry matter intake through cladodes was 237–243 g in opuntia-based diets. Dry matter intake was lowest (P < 0.02) in OC diets 61 g to that of 74 g/kgW0.75 in CC or OCG diets. Total tract apparent digestibility of DM, CP and GE were lower in OC diets than CC and OCG diets and these were not different between CC and OCG diets. DCP, DE and ME content and intakes were similar in CC or OCG diets, and were significantly higher than in OC diet. Urinary excretion of purine derivatives and microbial N supply were low in animals fed opuntia diets. Ruminal fluid pH increased due to opuntia feeding. Total N and NH3-N in ruminal fluid was lower in OC diet. TVFA, acetate and butyrate were higher (P < 0.01) in CC diets, whereas propionate was similar in all three diets. It is concluded that opuntia cladodes and roughage diets require an additional supplementation of organic N source, which improve dry matter intake, apparent digestibility, nutritive value, plane of nutrition and ruminal N and NH3-N. However, impaired microbial protein supply on opuntia diets needs further studies. © 2005 Published by Elsevier B.V.