Effects of Eprinomectin on Bull Reproductive Performance

  • Claire Andresen (Iowa State University)
  • Patrick J. Gunn (Iowa State University)


Parasitic infections in cattle are known to negatively impact cattle performance. It has been demonstrated that anthelmintic treatment that reduces or eliminates worm load can positively influence cattle productivity by increasing a plethora of parameters including weight gain, reproductive efficiency, and carcass characteristics. While parasitic infections pose threats to all cattle, bulls have been found to be more susceptible than their female counterparts and tend to acquire higher worm loads more quickly. While an increased susceptibility in bulls is recognized, little research has been done to determine the effect of anthelmintic treatment on bull reproductive performance and semen quality. This study evaluated the effects of eprinomectin on performance parameters and reproductive function in bulls during the summer grazing and breeding season. We observed no differences in BW and BCS between treatment with either injectable eprinomectin or injectable doramectin. Likewise, semen and reproductive parameters including motility, morphology, scrotal circumference, and scrotal tone were not affected by treatment. Overall, both treatments effectively reduced internal parasite loads during the breeding season. Results from this study that eprinomectin does not negatively impact production or reproductive parameters in reproductively active bulls and is effective at reducing parasitic infection over the course of the breeding season.

How to Cite:

Andresen, C. & Gunn, P. J., (2017) “Effects of Eprinomectin on Bull Reproductive Performance”, Iowa State University Animal Industry Report 14(1). doi:

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Published on
01 Jan 2017
Peer Reviewed