Animal performance and nutrient digestibility of feedlot steers fed a diet supplemented with a mixture of direct-fed microbials and digestive enzymes

ABSTRACT The objective of this study was to evaluate the effect of a mixture of direct-fed microbials (DFM), yeast, and digestive enzymes on animal performance in feedlot cattle, as well as digestibility when finishing feedlot cattle. Thirty crossbreed (Charolais × Beefmaster) steers averaging 15 months old and 321.83±3.73 kg of initial body weight were used. Animals were randomly assigned to one of two treatment groups: control (basal diet) and a mixture of DFM, yeast, and digestive enzymes (basal diet + 30 g of the mixture). Each group contained fifteen experimental units. Animals were fed individually twice a day, and dry matter intake (DMI) was recorded daily. Body weights were recorded initially and subsequently at 28-day intervals for a total of 140 days to evaluate average daily gain (ADG). The gain:feed ratio (G:F) was also calculated per period. Dry matter digestibility, crude protein (CPD), and neutral detergent fiber (NDFD) were evaluated in the finishing phase. Ten steers per treatment were randomly selected for digestibility evaluations. Insoluble acid detergent fiber was used to calculate apparent digestibility. A completely randomized design with measurements repeated over time was used to evaluate animal performance, and a completely randomized design was used to evaluate apparent digestibility. No effect of treatment was observed for DMI. At the end of the trial, differences for ADG were found between treatments, with higher values in control than the treatment group. However, no effect for G:F was found. Dry matter digestibility, CPD, and NDFD were similar between treatments. The addition of the mixture of DFM, yeast, and digestive enzymes as a feed supplement in the diet of feedlot cattle does not improve animal performance and nutrient digestibility.