A NOTE ON THE EFFECTS OF DIETARY INCLUSION OF A YEAST CULTURE ON GROWTH AND RUMINAL METABOLISM OF LAMBS GIVEN DIETS CONTAINING UNGROUND PELLETED MOLASSED DRIED SUGAR-BEET PULP AND BARLEY IN VARIOUS PROPORTIONS

Twenty-eight Suffolk-cross male castrated lambs aged 7 to 8 months, initial live wight 36 (s.e. 1.49) kg were given four diets which contained unground pelleted molassed sugar-beet pulp and rolled barley (940 g/kg, fresh weight basis) in the following proportions either A, 0.8 to 0.2 or B, 0.5 to 0.5, with 60 g soya-bean meal per kg. Diets A and B were offered with or without a yeast culture product Yea-Sacc. Diets were offered twice daily to appetite with 100 g hay per head. Yeast culture had no effect on any measurement made (P > 0.05). Lambs given diet B consumed more dry matter (DM), grew faster and had superior food conversion efficiencies (all P < 0.01). Rumen fluid taken 3 h after feeding contained higher concentrations of ammonia (P < 0.01), total volatile fatty acids (P < 0.001) and acetic acid (P < 0.001) in samples from lambs given diet A. Rumen fluid samples collected before the 10.00 h meal, produced more gas from diet A than diet B after 6 and 24 h in vitro incubation (P < 0.001) suggesting the presence of more undigested food. When ground diets were incubated, more gas was produced from diet A after 6 h (P < 0.05) but not after 24 h (P > 0.05). It is suggested that diet B supported faster growth of the lambs as a result of faster rate of digestion, higher DM intake and superior food conversion.