Date of Graduation
Doctor of Philosophy in Animal Science (PhD)
Jeremy G. Powell
Elizabeth B. Kegley
Second Committee Member
Thomas A. Yazwinski
Third Committee Member
Kelly M. Loftin
Biological sciences; Long-acting eprinomectin; Moxidectin; Oxfendazole; Performance; Replacement heifers; Spring-calving cows
Experiment 1, 83, newly weaned, fall-born crossbred heifer calves were allocated randomly to 1 of 3 anthelmintic treatments: 1) control (CON); 2) combination pour-on moxidectin and oxfendazole (MO); and 3) long-acting eprinomectin (LAE). Two preplanned orthogonal contrast statements were used: 1) to compare CON to treated cattle; and 2) to compare OXF to LAE. Heifer BW and BCS were greater (P≤0.02) from MO and LAE on d 112, 140, 154, 168, 182 compared to CON. Heifer cyclicity, estrous detection, natural service and overall pregnancy rates were greater (P≤0.02) for MO and LAE compared to CON. Cattle fecal egg counts (FEC) were greater (P<0.01) for CON compared to treated heifers and greater (P<0.01) for LAE compared to MO. Concentrations of white blood cells, lymphocytes, eosinophils, basophils, red blood cells, and platelets were greater (P≤0.02) for CON compared to treated heifers. Experiment 2, 90, spring-calving cows were allocated randomly to 1 of 3 anthelmintic treatments: 1) CON; 2) oxfendazole (OXF); and 3) LAE. Similar contrast statements were utilized. Cow BW, BCS on d 0, 91, 146, and 228, and pregnancy rate did not differ (P>0.20) between CON and treated cows. Day 14 BCS tended (P=0.07) to be greater for CON compared to treated cows. Also, BCS was greater (P=0.01) and hair coat score was lower (P<0.01) for OXF compared to LAE on d 91. Pregnancy rate tended (P=0.08) to be lower for LAE compared with OXF. Over the duration of the study, cow FEC, concentrations of white blood cells and eosinophils were greater (P≤0.04) for CON compared to treated cows. At weaning calves were administered the same anthelmintic treatment as their dams. Calf BW on d 417 and 431 were greater (P≤0.03) for treated calves compared to CON. Calf weaning weights were lower (P=0.03) for LAE compared to OXF. Calf FEC and platelets were greater (P≤0.02) for CON compared to treated calves. Carcasses from CON steers had greater (P=0.02) longissimus area and lower (P=0.02) yield grade compared to carcasses from treated calves. Based on these two studies, anthelmintic treatment can improve gain and decrease FEC in cow/calf operations.
Backes, Elizabeth Ann, "Evaluation of Long-Acting Eprinomectin Compared to Conventional Anthelmintics in Cow/Calf Production" (2016). Theses and Dissertations. 1677.