Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract only
Publication Acceptance Date: 10/28/2004
Publication Date: 2/5/2005
Citation: Looper, M.L., Edrington, T.S., Flores, R., Rosenkrans, Jr, C.F., Nihsen, M.E., Aiken, G.E. 2005. Incidence of fecal shedding of E. coli 0157:H7 and salmonella in stocker steers grazing different forages. American Society of Animal Science Southern Section Meeting. Journal of Animal Science 83:(Suppl. 2):9. Interpretive Summary:
Technical Abstract: The incidence of fecal shedding of E. coli O157:H7 (EHEC) and Salmonella (SM) in stocker steers grazing different forages was determined in two experiments. In Exp. I, fecal samples were collected at d 0, 61 and 97 from crossbred (< 1/4 Bos indicus), yearling steers (initial BW = 260 ± 4 kg) grazing either endophyte-infected tall fescue (E+; n = 36) or common bermudagrass paddocks (CB; n = 32). On d 87, steers grazing E+ paddocks were confined to a dry-lot pen and fed CB hay ad libitum for 10 d. Fecal samples were collected at the end of the dry-lot phase (d 97). In Exp. II, fecal samples were collected twice from crossbred Angus steers (n = 30; initial BW = 314 ± 4 kg) grazing novel endophyte-infected tall fescue or E+ tall fescue for 63 d. Within forage type, steers were treated with either ivermectin (I) or fenbendazole (F). No steers shed SM during Exp. I. Further, no steers shed EHEC at d 0 but did at d 61 and 97. At d 61, forage type did not influence (P > 0.10) fecal shedding of EHEC. Incidence of fecal shedding of EHEC was 6.3 and 5.6% for CB and E+ steers, respectively. More steers grazing CB (22%) were shedding EHEC than E+ steers fed CB hay (0%) at d 97 (P < 0.01). Average daily gain tended (P < 0.10) to be reduced in steers shedding EHEC (0.87 ± 0.07 kg/d) than steers not shedding EHEC (1.0 ± 0.02 kg/d). In Exp. II, fecal shedding of EHEC was not influenced (P > 0.10) by forage or anthelmintic treatment. Overall, 3.3% of steers were shedding EHEC. Forage type did not affect (P > 0.10) fecal shedding of SM in steers. At the initial collection, 75% of steers were shedding SM, while only 3.3% of steers were shedding SM at the second collection. More I-treated steers (92%) were shedding SM than F-treated steers (60%) at the initial collection. There was not an anthelmintic x forage interaction for SM shedding (P > 0.10). Average daily gain was decreased (P < 0.05) in steers shedding SM and grazing E+ (0.68 ± 0.05 kg/d) compared with all other steers (1.1 ± 0.1 kg/d). Results suggest that nutritional alterations and anthelmintic treatment may influence fecal shedding of pathogenic bacteria in growing beef cattle.