Kochia hay that had elicited mild toxicosis in sheep and cattle when fed for 21 d was fed to young, growing steers to evaluate the efficacy of metoclopramide for preventing kochia toxicosis. Twelve steers (271 +/- 39 kg) were given ad libitum access to Kochia hay for 38 d. Six steers were dosed orally with 15 mg of metoclopramide/kg of BW three times each week in gelatin capsules, and six steers received empty gelatin capsules. Steers were housed in individual outside pens for the first 28 d, then inside in metabolism stalls for the last 10 d. Kochia intake averaged 1.2 +/- .04 and 1.1 +/- .05% of BW throughout 38 d for kochia-fed control and kochia plus metoclopramide-dosed steers, respectively. During the last 10 d, metoclopramide had no effect (P greater than .15) on digestibility of DM, OM, NDF, ADF, or CP. However, metoclopramide reduced N retention (P less than .01; 20 vs 8 g/d). Kochia hay decreased serum prolactin and insulin concentrations (P less than .01) from 12.4 to 1.5 ng/ml and from .53 to .23 ng/ml, respectively. Metoclopramide had no effect (P greater than .50) on prolactin or insulin in steers fed kochia hay. Serum growth hormone was not affected by kochia but was suppressed by metoclopramide in steers fed kochia hay (P less than .07). Serum bilirubin (total and unconjugated) was elevated (P less than .05), indicating early, mild hepatotoxicosis characteristic of kochia toxicosis. Kochia also increased serum concentrations of iron, total protein, albumin, globulin, and creatinine and decreased urea N (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)