Date of Award

Fall 2010

Project Type


Program or Major

Animal Science

Degree Name

Master of Science

First Advisor

Peter Erickson


The experiment compared the effects of chlortetracycline (CTC), lasalocid (L), and the combination (LCTC) on dairy heifers. Forty calves, 12 wk of age, were assigned to control (C), L (1 mg/kg BW/d), CTC (350 mg/d), or LCTC. Individual DMI was measured daily. Skeletal measures, BW, BCS, blood urea N and glucose concentrations were measured weekly. Calves received an external marker to estimate apparent total tract nutrient digestibilities. Total collection of urine was obtained from 20 calves to determine N retention. The DMI was higher (P=0.01) for CTC versus L and C, and DMI was lower for L versus LCTC. ADG was highest (P=0.10) for CTC. Withers height was shortest (P<0.01) for L. The BCS was higher (P<0.01) for CTC and LCTC. Treatments were not effective at improving nutrient utilization or N retention. The results indicate that CTC increases DMI, ADG, and BCS.