EFFECTS OF DIFFERENT FORMS OF POLYUNSATURATED FATTY-ACIDS ON RUMEN FERMENTATION AND TOTAL NUTRIENT DIGESTIBILITY OF SHEEP FED PRAIRIE HAY BASED DIETS

Four rumen cannulated sheep were used in a 4 x 4 Latin square design to investigate the effects of soy fatty acid infusion on ruminal fermentation, in sacco digestion and apparent total digestibility. The control diet (C) based on 78.0% prairie hay, 5.3% protein supplement and 16.7% whole barley, was compared to diets where soy oil (SO), emulsified soy oil (ESO) or calcium salts of soy oil fatty acids (CaSSO) replaced whole barley. Diets were formulated to be isonitrogenous and isoenergetic. Fat content in DM was 2.9% for diet C, 8.3 to 9.0% for supplemented diets. In sacco degradation of DM, ADF and NDF was not affected by lipid infusions during the first 24 h in the rumen. Total VFA and molar proportion of butyrate in prefeeding rumen fluid were lower with the SO diet compared with diet C: 53.3 vs. 81.6 mmol/l and 10.7 vs. 14.8%, respectively. Adding SO or ESO depressed apparent digestibilities of OM, ADF and NDF by 8.8 to 9.0%; depression of fiber digestion was reversed with diet CaSSO. Fat infusion increased total dietary lipid digestibility particularly with emulsifiers, 60.0, 73.9, 81.5 and 68.3% for diets C, SO, ESO and CaSSO, respectively. Calcium salts of polyunsaturated fatty acids were an effective energy source for ruminant rations.