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, in itial live wight 36 (s.e. 1.49) kg were given four diets which contain ed 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 w ere offered twice daily to appetite with 100 g hay per head. Yeast cul ture had no effect on any measurement made (P > 0.05). Lambs given die t B consumed more dry matter (DM), grew faster and had superior food c onversion efficiencies (all P < 0.01). Rumen fluid taken 3 h after fee ding contained higher concentrations of ammonia (P < 0.01), total vola tile fatty acids (P < 0.001) and acetic acid (P < 0.001) in samples fr om 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 undigeste d food. When ground diets were incubated, more gas was produced from d iet A after 6 h (P < 0.05) but not after 24 h (P > 0.05). It is sugges ted that diet B supported faster growth of the lambs as a result of fa ster rate of digestion, higher DM intake and superior food conversion.