Pathogen shedding by F1 Angus x Nellore cattle fed with distillery grains in Brazil

Abstract

Beef is one of the main foods involved in the occurrence of foodborne illnesses. Among the biological hazards, outbreaks caused by Escherichia coli producing Shiga toxin (STEC) and Salmonella spp. result in losses, regarding both public health aspects as well as technical and commercial barriers and returns of goods. During bovine slaughter, the skin is the main contamination source for the carcass and its contamination is related to the increase of the excretion in the feces of these bacteria. Numerous risk factors have been associated with increased excretion such as factors related to the diet. Diets with high fermentative rate have higher ruminal microbial metabolism, which causes a decrease in the concentration of volatile organic acids (VOA) and an increase of pH in the large intestine, a predilection site for the growth and multiplication of enterobacteria. Studies in the United States have shown that cattle fed with distillery grains (DG), a corn ethanol fermentation byproduct, show greater fecal pathogen excretion than cattle fed diets without DG. In view of the increased corn ethanol production in Brazil associated with the search for sustainable nutritional alternatives in animal production without jeopardizing public health, the objective of this study is to verify the excretion of pathogens in the feces of cattle fed with different levels of wet distillery grains (WDG). Fecal samples from 100 male bulls, 50% Angus and 50% Nellore, randomly divided into four diets (N = 25) consisting of different levels of WDG (0%, 15%, 30% and 45% of dry matter ) will be submitted to the quantification and occurrence of STEC and Salmonella spp. by means of the qPCR technique and the physical and chemical analysis for quantification of VOA, lactic acid, pH, starch, crude protein (CP), neutral detergent fiber (NDF) and acid (FDA). Statistical analyses will be performed by the statistical software SAS 9.4 at a level of significance of 5%. These results may generate technical-scientific subsidies to recommend the use of distillery grains in the diet of crossbred cattle in Brazilian confinements without affecting the food safety of the bovine meat in natura.Keywords: Bos indicus, contamination, feces, Salmonella spp., STEC, WDG (AU)