Effect of two dosage levels of doramectin on health, growth performance and carcass characteristics of finishing beef steers

Abstract

A total of 3446 crossbred Mexican-origin steers (average 625 lbs/284 kg) were utilized to determine the effect of administering doramectin at label-dose (full-dose, 200 mcg/kg body weight; 1 ml/110 lbs) vs. half-label dose (half-dose, 100 mcg/kg body weight; 1 ml/220 lbs) on health, growth performance and carcass characteristics of finishing beef steers. Health parameters, growth performance and carcass quality grade did not differ between treatments. However, there was a significant difference in the proportion of carcasses classified as USDA yield grades (YG) 2, 3 and 4. A higher proportion of carcasses in the full-dose treatment were scored YG 2 (P<0.0001), and a higher proportion of carcasses in the half-dose treatment were scored YG 3 (P=0.0014) and YG 4 (P=0.0112), suggesting steers treated with the full-dose treatment were leaner. These results indicate that there is no economic advantage to using the full dose (200 mcg/kg body weight) of doramectin in beef cattle.