369 Impact of an extended-release dewormer on fetal development and subsequent calf performance

Abstract

Abstract Parasitism decreases the nutrients available for cow and fetal/calf performance. The objective of this study was to evaluate the impact of an extended-release dewormer [LongRange® (eprinomectin)] compared to a traditional dewormer [Dectomax® (doramectin)] on fetal/calf performance. Postpartum suckled beef cows (n = 349) were grouped by age and randomly allotted to one of two treatments over a two year period 1) treatment with LongRange at AI and calves treated with Eprinex® or 2) cows and calves treated with Dectomax. In year 2, half of each treatment was switched to the opposite treatment and half remained on the same treatment to result in a 2x2 design (calf sex was included in the statistical model). Cow weight was determined at AI, d60, d135, and d365 (treatment year 2). Calves born in year 2 were weighed at time of AI and at weaning. Pregnancy rates (determined at 60 and 135 d after AI) did not differ in year 1 (P = 0.85, 0.29) or in year 2 (P = 0.44, 0.98). Both treatments lost weight from AI to d60 of the breeding season (P = 0.98); however, there was a weak tendency (P = 0.15) for LongRange cows to gain more from d60 to 135 compared to Dectomax cows. Performance did not differ from d135 to AI in year 2 (P = 0.79). Calves that were in utero during year 1 when their dam received LongRange treatment had increased weight per day of age at year 2 AI (mean calf age =58d) compared to Dectomax treatment (P = 0.05; 2.2 ± 0.09 vs 2.0 ± 0.07kg). Furthermore, year 2 treatment tended (P = 0.09) to impact weight per day of age at weaning (LongRange=1.4 ± 0.03kg, Dectomax=1.3 ± 0.02). There was no year 1 by year 2 interaction (P = 0.87). In summary, administering an extended-release dewormer at AI did not impact pregnancy success, but increased calf performance both at 50d of age and at weaning.