Date of Graduation


Document Type


Degree Name

Master of Science in Animal Science (MS)

Degree Level



Animal Science


Jeremy Powell

Committee Member

Tom Yazwinski

Second Committee Member

Beth Kegley


parasitology, beef cattle health, anthelmintic resistance, beef cattle productivity, livestock infection levels, anthelmintic product efficacy


Internal parasitism inevitability prompts economic loss in beef cattle production by decreasing growth performance and reproductive traits. Today, the most widely used class of anthelmintic used to treat parasitism, is the macrocyclic lactone. Many studies have conflicting results on the efficacy of macrocyclic lactones (ML) efficacy against internal parasitism. The objective of this study was to evaluate the effectiveness of moxidectin and eprinomectin, two of the MLs, on cow performance. Multiparous fall calving, crossbred beef cows (n = 106) were allocated randomly to 1 of 3 anthelmintic treatments: 1) Negative control (CON), in which cows did not receive an anthelmintic, 2) Injectable moxidectin (MOX) and 3) Injectable extended release eprinomectin (ERE). Anthelminthic administration occurred on d 0, just prior to calving. Body weights (BW), body condition scores (BCS), and fecal egg counts (FEC) were obtained throughout the duration of the calving season until weaning, occurring on days: 0, 80, 162, and 217, with weaning occurring on d217. FEC were obtained, and body weights were recorded for calves on d162 and d 217.Performance data were analyzed using the MIXED procedures of SAS, and pregnancy data were analyzed using the GENMOD procedures of SAS. Significance was fixed at P < 0.05 and tendencies were established from 0.05 ≤ P ≤ 0.10. There was no effect of anthelmintic treatment on cow BW (P ≥ 0.57) or cow BCS (P ≥ 0.22) during the 217 d study; however, CON cows tended to have lower BCS (P = 0.08) throughout the duration of the study. Cows treated with ERE had lower FEC compared to MOX and CON groups (P ≤ 0.001), as well as a tendency for improved pregnancy (2 = 0.0735), and calving (2 = 0.007) rates compared to the MOX treated group. Calf average daily gain (P = 0.23) and weaning weight (P = 0.35) was similar regarding CON, MOX, and ERE dam treatments. Calf fecal egg counts tended to differ in relation to dam treatment on d 162 (P = 0.08) regarding CON, MOX, and ERE cow treatments.