Date of Graduation

8-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level

Graduate

Department

Animal Science

Advisor

Jeremy G. Powell

Committee Member

Elizabeth B. Kegley

Second Committee Member

Thomas A. Yazwinski

Third Committee Member

Kelly M. Loftin

Keywords

Biological sciences; Long-acting eprinomectin; Moxidectin; Oxfendazole; Performance; Replacement heifers; Spring-calving cows

Abstract

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.

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