Influence of processed grains on fecal pH, starch concentration, and shedding of Escherichia coli O157 in feedlot cattle1

Abstract

Manipulation of cattle diets has been proposed as a possible preharvest control measure for Escherichia coli O157. Altering hindgut fermentation through diet changes may be a means to reduce fecal shedding of E. coli O157. In Exp. 1, the objective was to determine whether fecal shedding of E. coli O157 was related to fecal starch concentration. Beginning on d 20, and every week thereafter until d 61, steers in 54 pens (6 to 7 steers per pen) were sampled (n = 122) by fecal collection and rectoanal mucosal swabs (RAMS) for E. coli O157 and fecal starch concentration determinations. Escherichia coli O157 prevalence was 3.3% in fecal samples, 4.1% as measured by RAMS, and 4.9% by fecal or RAMS samples. Steers positive for E. coli O157 contained 21% more (P < 0.05) fecal starch than steers that were negative for E. coli O157. In Exp. 2, we attempted to alter the concentration of starch escaping rumen fermentation by feeding finishing diets based on steam-flaked corn (SFC) and dry-rolled corn (DRC) to 30 heifers prescreened for being culture positive for fecal E. coli O157. Beginning on d 13, heifers were sampled (feces and RAMS) weekly to monitor fecal pH and starch concentration, and prevalence of E. coli O157. Prevalence of E. coli O157 remained above 30% for the first 13 d, but declined (P < 0.05) over the entire 7-wk period. Based on RAMS, the prevalence of E. coli O157 tended to be greater (P = 0.08) for heifers fed SFC than for those fed the DRC diet. After d 20, heifers fed DRC had greater (P < 0.05) fecal starch and lower (P < 0.05) fecal pH than heifers fed SFC. Fecal pH was negatively correlated (r = - 0.34; P < 0.05; n = 143) with fecal starch concentration. Fecal starch concentration and pH were not different (P > 0.05) for heifers that were positive or negative for E. coli O157. Our data suggest that fecal shedding of E. coli O157 was not related to fecal pH or starch concentration in cattle fed grain-based diets.

Combined use of ionophore and virginiamycin for finishing Nellore steers fed high concentrate diets

“…Depenbusch et al (2008) also found that fecal pH is negatively correlated with FSC, even though the correlation coefficient was lower (-0.34). Dry matter intake was positively correlated (p ≤ 0.05; PCC = 0.23) with FSC, agreeing with the results reported by Galyean et al (1979).…”

<b>Performance of beef cattle bulls in feed lots and fed on diets containing enzymatic complex

“…Yeasts in the diet remove the oxygen in the viable cellulolytic bacteria which use lactic acid and a pH decrease of the ruminal contents occurs (Wallace, 2004). Fecal pH has an inversely proportional behavior to rumen degradation and fecal excretion of starch, as reported by Barajas and Zinn (1998) and Depenbusch et al (2008). Therefore, in diets with high grain inclusion, a greater quantity of starch does not undergo rumen fermentation and more starch passes through the small intestine.…”

Efeito do processamento do milho e dos teores de fibra no desempenho de bovinos Nelore em terminação

“…Estes autores também observaram que animais alimentados com grãos destilados, mas sem a inclusão de feno de alfafa apresentaram carcaças mais leves e magras em relação àqueles novilhos alimentados com 6% de feno de alfafa. Marques et al (2011) ao avaliar a utilização de grão de milho inteiro e a inclusão de três níveis de bagaço de cana-de-açúcar in natura (0, 3 ou 6% na MS da ração total) pode observar efeito quadrático de inclusão de bagaço para consumo de MS, ganho médio diário e peso de carcaça quente. Entretanto o desempenho de bovinos alimentados sem inclusão de bagaço foi inferior aqueles animais recebendo dietas com 3 ou 6% de bagaço.…”

“…MacDonald et al (2011) ao utilizar dietas a base de milho floculado, com inclusões de feno de alfafa de 7,5, 10 ou 12,5% e 25% de grãos de sorgo destilados, concluíram que com o aumento da inclusão de feno de alfafa houve tendência em aumentar linearmente o consumo de MS e a conversão alimentar.…”

“…May et al (2011) ao estudar inclusões de 7,5, 10 ou 12,5% de feno de alfafa, 0, 15 ou 30% de grãos destilados, verificaram que conforme houve aumento da inclusão de fibra de alfafa na dieta, houve queda linear para a eficiência alimentar e energia liquída para mantença e ganho das dietas.…”