Probióticos e ionóforo como aditivos para novilhos de corte

Abstract

The purpose of the literature review was to discuss some feed additives for use in cattle, addressing two classes, probiotics, and antibiotics, their mechanisms of action, and their effects when added to the diet of cattle. In article 1, different models for adjusting the in vitro gas production of corn silage and the effect of using the combination of three additives in the diet of beef steers were tested. Therefore, the objective of this work was to examine the effects of ruminal inoculum of steers receiving different combinations of ionophore and probiotics in their diets on the in vitro gas production of corn silage. Ruminal fluid from four crossbred steers with rumen cannula and assigned to a 4 × 4 Latin square were used in the following treatments: (1) Monensin; (2) Monensin + Bacillus toyonensis; (3) Monensin + Saccharomyces cerevisiae var. boulardii; and (4) Bacillus toyonensis + Saccharomyces cerevisiae var. boulardii. The gas production data were fitted to the models Gompertz, Groot, Ørskov, Brody, Richards, and Dual Pool Logistic. The addition of treatments caused changes in the rumen fluid extracted from the animals to the point of altering the kinetics of gas production in vitro, and the treatments Monensina and B. toyonensis + S. boulardii showed better kinetics of corn silage degradation. The Groot and Richards models had the best fit for data estimates than the others evaluated. In article 2, the objective was to evaluate the effects of the combination of Saccharomyces cerevisiae var. boulardii, Bacillus toyonensis, and monensin on the intake and apparent digestibility of nutrients, ruminal and blood variables of steers receiving a 70% concentrate diet. Four crossbred Bos taurus × B. indicus steers with a ruminal cannula and housed individually in a 4 x 4 Latin square design were used. The following treatments were mixed in their daily diet: Monensin only (MO), Monensin + Bacillus toyonensis (MBT), Monensin + Saccharomyces cerevisiae var. boulardii (MSB), and Bacillus toyonensis + Saccharomyces cerevisiae var. boulardii (BTSB). It was observed that the BTSB treatment, when provided to the animals, increased feed intake, and resulted in similar concentrations values to the OM treatment in blood, urinary, ruminal pH, ruminal ammoniacal nitrogen, total fatty acids, and nitrogen balance. However, when probiotics were associated with sodium monensin, no beneficial effect was observed in the evaluated variables. Based on the promising observations of the association of Bacillus toyonensis with Saccharomyces cerevisiae var. boulardii obtained in this thesis, further studies are suggested with this association of probiotics on the productive aspects so that it is recommended as an alternative performance enhancer for cattle.