Diagnosis of nitrate toxicosis in cattle, using biological fluids and a rapid ion chromatographic method

Herman J. Boermans From the Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph Ontario, Canada, N1G 2W1.

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 DVM, PhD

SUMMARY

An ion chromatographic method was used to simultaneously determine nitrate and nitrite ions in biological samples. Ultrafiltration was used to produce a proteinfree filtrate. Chloride interferences were eliminated by precipitation as the silver salt. Detection limits and average recoveries were 0.5 mg/L and 102% for nitrate and 0.2 mg/L and 78% for nitrite, respectively. Nitrate concentration was 2.1 ± 1.8 mg/L and 4.9 ± 0.8 mg/L in serum and ocular fluid of healthy cattle, respectively; nitrite was not detected.

A severe case of nitrate poisoning in cattle was described and used to study the concentrations of nitrate and nitrite in samples obtained under natural conditions. Nitrate concentration of acutely poisoned cattle was 35% lower in ocular fluid at 158.1 ± 51.4 mg/L, than in serum at 256.3 ± 113.4 mg/L. Nitrite was not detected, because of the long processing time (> 3 hours) required for samples obtained in the field. A gradual decrease in ocular fluid nitrate of 29.4% at 24 hours, 25.9% at 36 hours, 51.6% at 48 hours, and 73.2% at 60 hours was observed; however, concentrations remained diagnostically significant (73.2 mg/L) 60 hours after death. Twenty-four hours after poisoning, the serum nitrate concentration of severely ill (52.7 ± 51.9 mg/L) and moderately affected (12.4 ± 5.7 mg/L) cattle that survived was indicative of the severity of clinical signs previously observed. Nitrate in serum and ocular fluid was stable in samples stored for 24 hours at 23 C, 1 week at 4 C, and 1 month at −20 C.

SUMMARY

An ion chromatographic method was used to simultaneously determine nitrate and nitrite ions in biological samples. Ultrafiltration was used to produce a proteinfree filtrate. Chloride interferences were eliminated by precipitation as the silver salt. Detection limits and average recoveries were 0.5 mg/L and 102% for nitrate and 0.2 mg/L and 78% for nitrite, respectively. Nitrate concentration was 2.1 ± 1.8 mg/L and 4.9 ± 0.8 mg/L in serum and ocular fluid of healthy cattle, respectively; nitrite was not detected.

A severe case of nitrate poisoning in cattle was described and used to study the concentrations of nitrate and nitrite in samples obtained under natural conditions. Nitrate concentration of acutely poisoned cattle was 35% lower in ocular fluid at 158.1 ± 51.4 mg/L, than in serum at 256.3 ± 113.4 mg/L. Nitrite was not detected, because of the long processing time (> 3 hours) required for samples obtained in the field. A gradual decrease in ocular fluid nitrate of 29.4% at 24 hours, 25.9% at 36 hours, 51.6% at 48 hours, and 73.2% at 60 hours was observed; however, concentrations remained diagnostically significant (73.2 mg/L) 60 hours after death. Twenty-four hours after poisoning, the serum nitrate concentration of severely ill (52.7 ± 51.9 mg/L) and moderately affected (12.4 ± 5.7 mg/L) cattle that survived was indicative of the severity of clinical signs previously observed. Nitrate in serum and ocular fluid was stable in samples stored for 24 hours at 23 C, 1 week at 4 C, and 1 month at −20 C.

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