Effects of feeding fungal culture extract and animal-vegetable fat on degradation of hemicellulose and on ruminal bacterial growth in heifers.

Four Holstein heifers cannulated in the rumen and proximal duodenum were used to analyze effects of Aspergillus oryzae fermentation extract and yeast culture (Amaferm Micro-Mix. Biozyme Enterprises, Inc., St. Joseph, MO) and 5% animal-vegetable fat on ruminal and total tract digestibilities of nutrients. Heifers were assigned treatments in a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Few interactions between main effects were noted. Feeding fat decreased ruminal molar ratio of acetate:propionate. Rate of disappearance of potentially digestible NDF from orchardgrass hay was higher when heifers were fed fat. Thus, the lack of differences in digestibilities of NDF, ADF, or in the major hemicellulosic sugars is interpreted to suggest that 5% animal-vegetable fat had few toxic effects on ruminal microbes under the conditions of this study. Amaferm Micro-Mix tended to increase acetate:propionate in the rumen, but had little effect on site or extent of digestion of any of the fiber components measured. Efficiency of bacterial protein synthesis was not affected by treatment. Ruminal and total tract digestibilities of total hemicellulosic sugars were highly correlated (r = .82 and .72) with respective digestibilities of hemicellulose measured as NDF minus ADF.