Effects of Aspergillus oryzae prebiotic on animal performance, nutrients digestibility, and feeding behavior of backgrounding beef heifers fed with either a sorghum silage- or a byproducts-based diet.

This experiment evaluated the effects of the dietary inclusion or not of Aspergillus oryzae prebiotic (AOP; 2 g/d) in two contrasting diets: sorghum silage-based (SS) vs. byproducts-based (BP), on growth performance, nutrient digestibility, and feeding behavior of growing heifers. A total of 84 Angus crossbred heifers were used in the study. Heifers fed with the BP diets had greater feed intake, average daily gain, and final body weight. In addition, heifers fed with the BP diets had reduced number of visits to the feed bunk but consumed more in each visit than heifers fed with the SS diets. Additionally, heifers fed with the BP diets had lesser chewing activity measured in total min/d and in min/kg of dry matter intake; however, chewing activity measured in min/kg of neutral detergent fiber was not influenced by treatments. The inclusion of AOP increased the gain:feed ratio by 15% in heifers fed with the BP diet but did not influence this variable in the SS diet. The inclusion of AOP increased nutrient digestibility in heifers fed with the SS diet and decreased nutrient digestibility in heifers fed with the BP diet. These results show that feeding AOP can enhance growth performance in beef heifers in a diet-dependent manner.