Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2011
Publication Date: 7/29/2011
Citation: Taylor, J.B., Dungan, R.S., Lewis, G.S. 2011. Sodium chlorate reduces presence of Escherichia coli in feces of lambs and ewes managed in shed-lambing systems. Journal of Animal Science. 90:381-386.
Interpretive Summary: Neonatal diarrhea erodes profitability of sheep enterprises. Because diarrhea is transmissible, morbidity would be greater when sheep are in close proximity. For the sheep industry, this is of great importance, because nearly 50% of lambs in the U.S. are typically born in shed-lambing systems. Therefore, reduction of diarrhea morbidity should mitigate production losses associated with neonatal lambs. Our objective was to establish doses of orally-administered chlorate salt that reduced presence of generic E. coli in intestines of ewes and neonatal lambs managed in shed-lambing systems. Our results indicate that chlorate salt given in a single dose to yearling ewes may have application in reducing fecal shedding of diarrhea-causing bacteria (e.g., E. coli, Salmonella spp., Clostridium perfringens) from ewes managed in shed-lambing systems. Accomplishing this objective was the first step in evaluating the efficacy of chlorate salt as an oral prophylactic treatment for reducing the occurrence of bacterial-induced neonatal diarrhea. Reducing fecal shedding of diarrhea-causing bacteria should decrease the overall bacterial load in the environment and decrease the incidence of neonatal diarrhea.
Technical Abstract: Our objective was to establish doses of orally-administered NaClO3 that reduced presence of generic Escherichia coli in intestines of ewes and neonatal lambs managed in a shed-lambing system. Neonatal lambs (n = 32; age = 7.1 ± 1.2 d; BW = 6.8 ± 1.0 kg) and yearling ewes (n = 44; BW = 74.8 ± 5.6 kg) were used in two experiments. In both experiments, lambs and ewes were randomly assigned to 1 of 4 groups, and groups were randomly assigned to 1 of 4 treatments. In Exp. 1, neonatal lambs were given single, aqueous, oral doses of saline (control; NaCl, 30 mg/kg BW) or 30, 60 , or 90 mg of NaClO3/kg of BW. At 25.9 ± 1.3 h after treatment, lambs were euthanized, and their intestinal contents were collected aseptically. In Exp. 2, ewes were given single, aqueous, oral doses of saline (NaCl, 150 mg/kg BW) or 150, 300, or 450 mg of NaClO3/kg of BW. At 24.0 ± 0.8 h after treatment, fecal samples were collected aseptically from the rectum of each ewe. For both experiments, generic E. coli were enumerated from intestinal contents and feces within 4 to 12 h after collection. In Exp. 1, the effect (P = 0.08) of NaClO3 on presence of generic E. coli in colon contents was dose-dependent. This effect was linear (P < 0.01) and negative, which indicated that as NaClO3 dose increased, generic E. coli that could be isolated from colon contents decreased. Specifically, lambs dosed with 60 and 90 mg of NaClO3/kg of BW had fewer E. coli cfu/g of content than control lambs (P < 0.06). Lambs dosed with 90 mg of NaClO3/kg of BW had fewer E. coli cfu/g of content than lambs dosed with 30 mg of NaClO3/kg of BW (P = 0.09). Sodium chlorate dose did not influence (P = 0.58) presence of generic E. coli in contents collected from the cecum. In Exp. 2, the effect (P < 0.0001) of NaClO3 on presence of E. coli in fecal contents from ewes was dose-dependent. This effect was quadratic (P < 0.0001) and negative; ewes dosed with 150, 300, and 450 mg of NaClO3/kg of BW had fewer E. coli cfu/g of feces than control ewes. No differences in E. coli cfu/g of feces were detected between NaClO3 treatments (P = 0.88 to 0.97). Based on these results, a single oral dose of at least 60 and 150 mg of NaClO3/kg of BW in neonatal lambs and yearling ewes, respectively, significantly decreased the presence of generic E. coli in contents from the lower intestine.