| Abstract: | Monensin, an anticoccidial antibiotic, was incorporated into pelleted feed and given to 10-week-old Holstein-Friesian calves at 0.25 mg/kg, 1.0 mg/kg, or 2.0 mg/kg of body weight. Inoculated calves were inoculated by drenching with 500,000 sporulated oocysts of Eimeria bovis. Other calves served as inoculated or uninoculated controls. Observations were recorded on oocyst discharge in the feces, clinical signs, weight gain, food consumption, hemoglobin, packed cell volume, total serum protein, sodium and potassium content of the serum, and differential white cell counts. Calves in the inoculated control group developed severe infections, discharged large numbers of oocysts, developed clinical signs and 1 of 5 died. Uninoculated, untreated control calves were essentially free of coccidia. A few calves in the groups which received monensin developed light infections but none of them had clinical signs of coccidiosis. Calves which received the highest and the lowest dosages of monensin gained weight less rapidly than did the uninoculated controls or the animals which received monensin at 1.0 mg/kg of body weight. Inoculated control calves with severe infections had reduced food intake and a significant reduction in weight which was not regained during the experimental period. The only other significant change in any of the parameters measured was a reduction in the total serum protein of inoculated, nonmedicated control calves. The level returned to normal 5 weeks after clinical signs first appeared. |
