title: Continuous, low-dose oral exposure to sodium chlorate reduces fecal generic Escherichia coli in sheep feces without inducing clinical chlorate toxicosis.
abstract: Our objectives were to determine an effective, yet safe, daily dose of sodium chlorate for reducing fecal shedding of generic Escherichia coli in mature ewes. In a completely randomized experimental design, 25 Targhee ewes (age ∼ 18 mo; BW = 62.5 ± 7.3 kg, mean ± SD) were assigned randomly to 1 of 5 sodium chlorate treatments, which were administered in the drinking water for 5 consecutive days. Treatments were control group (no sodium chlorate) and 4 targeted levels of daily sodium chlorate intake: 30, 60, 90, and 120 mg · kg(-1) BW · d(-1) for 5 d. Individual ewe ad libitum intake of water (with treatments) was measured daily, and BW was measured at the beginning of and 15 and 51 d after the 5-d treatment period. Serum chlorate, whole blood methemoglobin and packed-cell volume (PCV), and fecal generic E. coli and general Enterobacteriaceae coliforms were measured from corresponding samples collected at the end of the 5-d treatment period. Average daily intakes of sodium chlorate from drinking water treatments were 95%, 91%, 90%, and 83% of the target treatment intakes of 30, 60, 90, and 120 mg · kg(-1) BW · d(-1), respectively. Daily sodium chlorate intake remained constant for all treatment groups except for ewes offered 120 mg NaClO3 · kg(-1) BW · d(-1), which decreased (quadratic; P = 0.04) over the course of the 5-d treatment period. This decrease in sodium chlorate intake indicated that the 120-mg NaClO3 level may have induced either toxicity and/or an aversion to the drinking water treatment. Serum chlorate concentrations increased (quadratic; P < 0.001) with increasing sodium chlorate intake. At the end of the 5-d treatment period, mean (least squares ± SEM) serum chlorate concentrations for ewes offered 30, 60, 90, and 120 mg NaClO3 · kg(-1) BW · d(-1) were 15.6 ± 14.1, 32.8 ± 15.8, 52.9 ± 14.1, and 90.3 ± 14.1 μg/mL, respectively. Whole blood methemoglobin and PCV were similar (P = 0.31 to 0.81) among the control group and ewes offered sodium chlorate. Likewise, BW was not affected by sodium chlorate (P > 0.27). Ewes consuming approximately 55 mg NaClO3 · kg(-1) BW · d(-1) or more (i.e., ewes offered 60, 90, and 120 mg) had a >1.4 log unit reduction in fecal E. coli and Enterobacteriaceae coliforms compared with control ewes. We suggest that for a short-term, 5-d dosing strategy, 55 to 81 mg NaClO3 · kg(-1) BW · d(-1) is an effective, yet safe, daily oral dose range for mature ewes to achieve a 97% to 99% reduction in fecal shedding of generic E. coli.
authors.forename: J B
authors.initials: JB
authors.lastname: Taylor
authors.forename: D J
authors.initials: DJ
authors.lastname: Smith
mesh_terms: D000284:Administration, Oral; D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002704:Chlorates / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000662:veterinary*; D005243:Feces / Q000382:microbiology*; D005260:Female; D006540:Herbicides / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D008706:Methemoglobin / Q000378:metabolism; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy* / Q000382:microbiology; D034561:Sheep, Domestic / Q000382:microbiology* / Q000502:physiology; D000069436:Toxicological Phenomena / Q000187:drug effects; D016896:Treatment Outcome
chemical_list: D002704:Chlorates; D006540:Herbicides; D008706:Methemoglobin; C032706:sodium chlorate