Este trabalho objetivou verificar se o prebiótico a base de parede celular de Saccharomyces cerevisiae reduz coliformes totais, Escherichia coli e Salmonella spp da pele, fezes e da carcaça de bovinos terminados em confinamento. Para tanto, 18 novilhos, ½ sangue Angus  foram submetidos a três tratamentos diários durante 105 dias: controle (n=6),  Lev4g (dieta com 4 g de levedura por animal dia-1, n=6) ou Lev 7g ( dieta com 7 g de levedura por animal dia-1, n=6). Nos dias 29 e 90 após a entrada no confinamento, coletou-se amostras de fezes, swab de pele, água e alimento para contagem de Escherichia coli e coliformes totais e isolamento de Salmonella spp. No dia do abate, realizou-se coleta nas carcaças para identificação de Salmonella spp e quantificação de Escherichia coli, coliformes totais, mesófilos. Notou-se redução de Escherichia coli e coliformes totais nas amostras de fezes (P=0,0001 e 0,001 respectivamente) e de Escherichia coli, coliformes totais  e aeróbios mesófilos na carcaça (P=0,06; 0,10 e 0,05 respectivamente) nos grupos tratados. Houve ausência de Salmonella spp. em todas as coletas realizadas. Concluiu-se que a suplementação reduziu a excreção fecal e consequentemente, a contaminação da carcaça pela Escherichia coli, mesófilos e coliformes totais dos animais confinados, sendo uma medida sanitária benéfica e livre de resíduos para melhorar a qualidade microbiológica da carne.

The use of feed additives based on yeast cell wall has already been studied to favor the growth of beneficial intestinal bacteria to the detriment of pathogenic bacteria in ruminants. This fact reduces diarrhea, increases animal performance, and could promote lesser contamination of the bovine carcass at the time of slaughter, during the evisceration. The present study aims to verify if the yeast cell wall of Saccharomyces cerevisiae autolyzed yeast (AY) reduces total coliforms and Escherichia coli in feces and bovine carcass. Therefore, 36 steers, ½ Angus blood, finished in a feedlot, were submitted to three daily treatments for 105 days: control (diet without yeast), AY 4g (4g/animal/day, 2 x 1010cel/g of a commercial product based on Saccharomyces cerevisiae RumenYeast®), AY 7g (7g/animal/day, RumenYeast®). On days 29 and 90, after beginning in the feedlot, samples of feces were collected for E. coli and total coliforms identifications and counting. On the day of slaughter, 4 points of the carcasses were collected to identify and quantify E. coli, total fecal coliforms, and mesophiles by a petrifilm methodology. There was a reduction in E. coli and total coliforms for the AY 7g in the fecal samples comparing to the other groups (P = 0.0008 and 0.008, respectively), and a trend to reduce E. coli, total coliforms and mesophilic aerobes in the bovine carcass in AY 4g and AY 7g, comparing to the control group (P = 0.06; 0.10, and 0.05, respectively). It was concluded that supplementation with autolyzed yeast, especially when utilized in higher doses (7g), reduced fecal excretion and, consequently, reduce the carcass contamination by E. coli, mesophiles, and, total coliforms in animals during the feedlot period.