Kochia (Kochia scoparia) toxicosis in cattle: results of four experimental grazing trials.

Four kochia grazing trials were completed over a period of 3 years. Yearling steers were allowed to graze pure stands of irrigated and fertilized kochia (Kochia scoparia) for periods of 14 to 105 days. A total of 116 steers were given kochia as their sole forage. Twenty control steers were allowed to graze native grass pasture, and 20 steers were allowed to graze both native grass and kochia pastures. Steers grazing only kochia lost weight or gained poorly compared with control steers grazing native grass. Steers that grazed both kochia and native grass had intermediate rates of gain. Signs of toxicosis were observed only in steers grazing kochia alone. Considerable variability in the degree of toxicosis was observed from one year to another. Morbidity in the steers grazing only kochia varied from 0% (Trial 4) to 28% (Trial 1), and mortality varied from 0% (Trials 3 and 4) to 10% (Trial 2). The most common signs observed in clinically affected steers were depression, dehydration, weight loss, muscular weakness, photosensitization, ocular discharge, and crusty muzzle. In all 4 trials, significant elevations in serum glutamic oxaloacetic transaminase (GOT) and serum gamma glutamyl transpeptidase (GGT) were observed in steers grazing kochia. In 3 of the 4 trials, significant elevations in serum bilirubin, serum calcium, and serum protein were also observed in kochia-fed steers. Necropsies were performed on 6 of 9 steers that died or were euthanized. The primary pathologic findings were severe chronic nephrosis (5 steers) and degenerative hepatopathy (5 steers).(ABSTRACT TRUNCATED AT 250 WORDS)