Tissue distribution, elimination, and metabolism of dietary sodium [36Cl]chlorate in beef cattle

The fate of sodium chlorite in simulated gastric and intestinal fluids and residues of chlorate in broiler chickens after oral administration of sodium chlorite

The fate of sodium [³⁶Cl]chlorite in simulated intestinal fluids and residues of chlorate in broiler chickens fed 0, 10, 100, or 1000 mg•kg^-1 of dietary sodium chlorite for 7 days was determined. [³⁶Cl]Chlorite was stable in water and simulated intestinal fluid during 6 h incubations but was rapidly degraded to chlorine dioxide, sodium chloride, and sodium chlorate in simulated gastric fluids. Addition of starch, citrate, or soybean shifted the relative proportions of chloroxyanions formed; addition of ferrous chloride caused quantitative formation of sodium chloride in gastric and intestinal fluids. [³⁶Cl]Chlorite underwent reductive transformation when fortified into chicken serum. Residues of chlorate in broiler chickens ranged from 3.5 to 374 ng•g^-1 in gizzard, were <6.8 to 126 ng•g^-1 in liver and were <7.2 to 190 ng•g^-1 in muscle when slaughtered with no withdrawal period. Data are presented suggesting that reductive processes govern the fate of chlorite when present in closed biological systems.

Distribution, Identification, and Quantification of Residues after Treatment of Ready-To-Eat Salami with 36Cl-Labeled or Nonlabeled Chlorine Dioxide Gas

When ready-to-eat salami was treated in a closed system with ³⁶Cl-labeled ClO₂ (5.5 mg/100 g of salami), essentially all radioactivity was deposited onto the salami. Administered ³⁶ClO₂ was converted to ³⁶Cl-chloride ion (>97%), trace levels of chlorate (<2%), and detectable levels of chlorite. In residue studies conducted with nonlabeled ClO₂, sodium perchlorate residues (LOQ, 4 ng/g) were not formed when reactions were protected from light. Sodium chlorate residues were present in control (39.2 ± 4.8 ng/g) and chlorine dioxide treated (128 ± 31.2 ng/g) salami. If sanitation occurred under conditions of illumination, detectable levels (3.7 ± 1.5 ng/g) of perchlorate were formed along with greater quantities of sodium chlorate (183.6 ± 75.4 ng/g). Collectively, these data suggest that ClO₂ is chemically reduced by salami and that slow-release formulations might be appropriate for applications involving the sanitation of ready-to-eat meat products.

Chloroxyanion Residues in Cantaloupe and Tomatoes after Chlorine Dioxide Gas Sanitation

Chlorine dioxide gas is effective at cleansing fruits and vegetables of bacterial pathogens and(or) rot organisms, but little data are available on chemical residues remaining subsequent to chlorine gas treatment. Therefore, studies were conducted to quantify chlorate and perchlorate residues after tomato and cantaloupe treatment with chlorine dioxide gas. Treatments delivered 50 mg of chlorine dioxide gas per kg of tomato (2-h treatment) and 100 mg of gas per kg of cantaloupe (6-h treatment) in sealed, darkened containers. Chlorate residues in tomato and cantaloupe edible flesh homogenates were less than the LC-MS/MS limit of quantitation (60 and 30 ng/g respectively), but were 1319 ± 247 ng/g in rind + edible flesh of cantaloupe. Perchlorate residues in all fractions of chlorine dioxide-treated tomatoes and cantaloupe were not different (P > 0.05) than perchlorate residues in similar fractions of untreated tomatoes and cantaloupe. Data from this study suggest that chlorine dioxide sanitation of edible vegetables and melons can be conducted without the formation of unwanted residues in edible fractions.

Distribution and chemical fate of ³⁶Cl-chlorine dioxide gas during the fumigation of tomatoes and cantaloupe

The distribution and chemical fate of (36)Cl-ClO2 gas subsequent to fumigation of tomatoes or cantaloupe was investigated as were major factors that affect the formation of chloroxyanion byproducts. Approximately 22% of the generated (36)Cl-ClO2 was present on fumigated tomatoes after a 2 h exposure to approximately 5 mg of (36)Cl-ClO2. A water rinse removed 14% of the radiochlorine while tomato homogenate contained ∼63% of the tomato radioactivity; 24% of the radiochlorine was present in the tomato stem scar area. Radioactivity in tomato homogenate consisted of (36)Cl-chloride (≥80%), (36)Cl-chlorate (5 to 19%), and perchlorate (0.5 to 1.4%). In cantaloupe, 55% of the generated (36)Cl-ClO2 was present on melons fumigated with 100 mg of (36)Cl-ClO2 for a 2 h period. Edible cantaloupe flesh contained no detectable radioactive residue (LOQ = 0.3 to 0.4 μg/g); >99.9% of radioactivity associated with cantaloupe was on the inedible rind, with <0.1% associated with the seed bed. Rind radioactivity was present as (36)Cl-chloride (∼86%), chlorate (∼13%), and perchlorate (∼0.6%). Absent from tomatoes and cantaloupe were (36)Cl-chlorite residues. Follow-up studies have shown that chlorate and perchlorate formation can be completely eliminated by protecting fumigation chambers from light sources.

Effect of intravenous or oral sodium chlorate administration on the fecal shedding of Escherichia coli in sheep

The effect of gavage or intravenous (i.v.) administration of sodium chlorate salts on the fecal shedding of generic Escherichia coli in wether lambs was studied. To this end, 9 lambs (27 ± 2.5 kg) were administered 150 mg NaClO3/kg BW by gavage or i.v. infusion in a crossover design with saline-dosed controls. The crossover design allowed each animal to receive each treatment during 1 of 3 trial periods, resulting in 9 observations for each treatment. Immediately before and subsequent to dosing, jugular blood and rectal fecal samples were collected at 4, 8, 16, 24, and 36 h. Endpoints measured were fecal generic E. coli concentrations, blood packed cell volume (PCV), blood methemoglobin concentration, and serum and fecal sodium chlorate concentrations. Sodium chlorate had no effects (P > 0.05) on blood PVC or methemoglobin. Fecal generic E. coli concentrations were decreased (P < 0.05) approximately 2 log units (99%) relative to controls 16 and 24 h after sodium chlorate infusion and 24 h after sodium chlorate gavage. Within and across time and treatment, fecal chlorate concentrations were highly variable for both gavage and i.v. lambs. Average fecal sodium chlorate concentrations never exceeded 100 µg/g and were typically less than 60 µg/g from 4 to 24 h after dosing. Times of maximal average fecal sodium chlorate concentration did not correspond with times of lowered average generic E. coli concentrations. Within route of administration, serum sodium chlorate concentrations were greatest (P < 0.01) 4 h after dosing; at the same time point, serum chlorate was greater (P< 0.01) in i.v.-dosed lambs than gavaged lambs but not at 16 or 24 h (P > 0.05). At 8 h, serum chlorate concentrations of gavaged lambs were greater (P < 0.05) than in i.v.-dosed lambs. Serum chlorate data are consistent with earlier studies indicating very rapid transfer of orally dosed chlorate to systemic circulation, and fecal chlorate data are consistent with earlier data showing the excretion of low to marginal concentrations of sodium chlorate in orally dosed animals. Efficacy of sodium chlorate at reducing fecal E. coli concentrations after i.v. infusion suggests that low concentrations of chlorate in gastrointestinal contents, delivered by biliary excretion, intestinal cell sloughing, or simple diffusion, are effective at reducing fecal E. coli levels. Alternatively, chlorate could be eliciting systemic effects that influence fecal E. coli populations.

Chlorate analyses in matrices of animal origin

Sodium chlorate is being developed as a potential food-safety tool for use in the livestock industry because of its effectiveness in decreasing concentrations of certain Gram-negative pathogens in the gastrointestinal tracts of food animals. A number of studies with sodium chlorate in animals have demonstrated that concentrations of chlorate in meat, milk, wastes, and gastrointestinal contents range from parts per billion to parts per thousand, depending upon chlorate dose, matrix, and time lapse after dosing. Although a number of analytical methods exist for chlorate salts, very few were developed for use in animal-derived matrices, and none have anticipated the range of chlorate concentrations that have been observed in animal wastes and products. To meet the analytical needs of this development work, LC-MS, ion chromatographic, and colorimetric methods were developed to measure chlorate residues in a variety of matrices. The LC-MS method utilizes a Cl(18)O(3)(-) internal standard, is applicable to a variety of matrices, and provides quantitative assessment of samples from 0.050 to 2.5 ppm. Due to ion suppression, matrix-matched standard curves are appropriate when using LC-MS to measure chlorate in animal-derived matrices. A colorimetric assay based on the acid-catalyzed oxidation of o-tolidine proved valuable for measuring ≥20 ppm quantities of chlorate in blood serum and milk, but not urine, samples. Ion chromatography was useful for measuring chlorate residues in urine and in feces when chlorate concentrations exceeded 100 ppm, but no effort was made to maximize ion chromatographic sensitivity. Collectively, these methods offer the utility of measuring chlorate in a variety of animal-derived matrices over a wide range of chlorate concentrations.

Fate of chlorate present in cattle wastes and its impact on Salmonella Typhimurium and Escherichia coli O157:H7

Chlorate salts are being developed as a feed additive to reduce the numbers of pathogens in feedlot cattle. A series of studies was conducted to determine whether chlorate, at concentrations expected to be excreted in urine of dosed cattle, would also reduce the populations of pathogens in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate in cattle wastes. Chlorate salts present in a urine-manure-soil mixture at 0, 17, 33, and 67 ppm had no significant effect on the rates of Escherichia coli O157:H7 or Salmonella Typhimurium inactivation from batch cultures. Chlorate was rapidly degraded when incubated at 20 and 30 degrees C with half-lives of 0.1 to 4 days. Chlorate degradation in batch cultures was slowest at 5 degrees C with half-lives of 2.9 to 30 days. The half-life of 100 ppm chlorate in an artificial lagoon system charged with slurry from a feedlot lagoon was 88 h. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively, these results suggest that chlorate administered to cattle and excreted in wastes would have no significant secondary effects on pathogens present in mixed wastes on pen floors. Lack of chlorate efficacy was likely due to low chlorate concentrations in mixed wastes relative to chlorate levels shown to be active in live animals, and the rapid degradation of chlorate to chloride at temperatures of 20 degrees C and above.

The in vitro reduction of sodium [36Cl]chlorate in bovine ruminal fluid1,2

Sodium chlorate effectively reduces or eliminates gram-negative pathogenic bacteria in the gastrointestinal tracts of live cattle. Limitations to the in vivo efficacy of chlorate are its rapid absorption from the gastrointestinal tract and its presumed reduction to chloride within the gastrointestinal tract. We hypothesized that chlorate would be reduced via ruminal bacteria in a ruminal in vitro system and that the reduction of chlorate would be influenced by the dietary for-age:concentrate ratio; thus, 4 ruminally cannulated steers were fed 20 or 80% concentrate diets in a crossover design. Ruminal fluid was collected in 2 periods and dispensed into in vitro tubes containing sodium [36Cl]chlorate, which was sufficient for 100 or 300 mg/L final chlorate concentrations. The tubes were incubated for 0, 1, 4, 8, 16, or 24 h; autoclaved, control ruminal fluid, fortified with sodium [36Cl]chlorate, was incubated for 24 h. Chlorate remaining in each sample was measured by liquid scintillation counting after [36Cl]chloride was precipitated with silver nitrate. A preliminary study indicated that chlorite, a possible intermediate in the reduction of chlorate, had a half-life of approximately 4.5 min in freshly collected (live) ruminal fluid; chlorite was, therefore, not specifically measured in ruminal incubations. The chlorate dose did not affect in vitro DM digestion (P > or = 0.11), whereas in vitro DM digestibility was decreased (P < or = 0.05) by 80% forage content. By 24 h, 57.5 +/- 2.6% of the chlorate remained in 100-mg/L incubations, whereas 78.2 +/- 2.6% of the chlorate remained in the 300-mg/L incubations. When the data were expressed on a concentration basis (mg/L), diet had no effect (P > or = 0.18) on chlorate reduction; however, when chlorate reduction was expressed on a percentage basis, chlorate reduction tended to be greater (P > or = 0.09) at 8 and 16 h in the incubations containing the low-concentrate diet. Chlorate remaining in autoclaved controls at 24 h was intermediate (P < 0.01) between chlorate remaining in live ruminal fluid samples incubated for 0 or 24 h. Attempts to isolate chlorate-respiring bacteria from 2 sources of ruminal fluid were not successful. These data indicate that microbial-dependent or chemical-dependent, or both, reduction of chlorate occurs in bovine ruminal fluid and that dietary concentrate had a negligible effect on chlorate reduction.

HPLC determination of chlorate metabolism in bovine ruminal fluid

Salmonella and Escherichia coli are two bacteria that are important causes of human and animal disease worldwide. Chlorate is converted in the cell to chlorite, which is lethal to these bacteria. An HPLC procedure was developed for the rapid analysis of chlorate (ClO(3)(-)), nitrate (NO(3)(-)), and nitrite (NO(2)(-)) ions in bovine ruminal fluid samples. Standard curves for chlorite, nitrite, nitrate, and chlorate were well defined linear curves with R(2) values of 0.99846, 0.99106, 0.99854, and 0.99138, respectively. Concentrations of chlorite could not be accurately determined in bovine ruminal fluid because chlorite reacts with or binds a component(s) or is reduced to chloride in bovine ruminal fluid resulting in low chlorite measurements. A standard curve ranging from 25 to 150 ppm ClO(3)(-) ion was used to measure chlorate fortified into ruminal fluid. The concentration of chlorate was more rapidly lowered (P < 0.01) under anaerobic compared to aerobic incubation conditions. Chlorate alone or chlorate supplemented with the reductants sodium lactate or glycerol were bactericidal in anaerobic incubations. In anaerobic culture, the addition of sodium formate to chlorate-fortified ruminal fluid appeared to decrease chlorate concentrations; however, formate also appeared to moderate the bactericidal effect of chlorate against E. coli. Addition of the reductants, glycerol or lactate, to chlorate-fortified ruminal fluid did not increase the killing of E. coli at 24 h, but may be useful when the reducing equivalents are limiting as in waste holding reservoirs or composting systems required for intense animal production.

Pharmacokinetics of ruminally dosed sodium [36Cl]chlorate in beef cattle

The recently recognized potential of sodium chlorate as a possible preharvest food safety tool for pathogen reduction in meat animals has spurred interest in the pharmacokinetics of intraruminally dosed chlorate. Six Loala cattle were assigned (one heifer and one steer per treatment) to one of three intraruminal doses of radiolabeled sodium [36Cl]chlorate (21, 42, or 63 mg/kg body weight) administered in four equal aliquots over a 24-h period. Blood and serum were collected (29 samples in 48 h). Total radioactive residues were measured and the radioactive moieties were speciated. Chlorate appeared rapidly in blood and serum after dosing. For animals administered a dose of 42 or 63 mg/kg, the half-life of absorption was estimated at 0.6-0.9 h. Serum chlorate concentrations progressively increased with aliquot administration until peaking at 6-21 parts per million at 26 h. Between aliquot administrations, serum chlorate levels typically peaked in 3.5 h or less. The half-life of chlorate elimination ranged between 6.9 and 11 h, depending on the dose. Ultimately, absorption of chlorate removes it from its desired site of action, the lower gastrointestinal tract, thereby reducing its efficacy. Further research is needed to develop a chlorate formulation that will allow passage to the lower gastrointestinal tract.