Comparison of serum progesterone curves in beef heifers during luteolysis after administration of dinoprost in the muscle or the ischiorectal fossa

Abstract

Many producers and veterinarians report injection of products in the rear legs or hip due to convenience or lack of access to the neck. Provision of an acceptable injection site that can be accessed from behind the cow for administration of therapeutics may improve compliance and beef products. The authors propose the ischiorectal fossa (IRF), located adjacent to the tailhead and craniomedial to the tuber ischia, as an alternate injection site for products in cattle. A suitable drug to use for proof of concept is Prostaglandin F2α (PGF2α), given that the physiological outcome variable (luteolysis) is detected by a decline in serum progesterone. Colazo et al demonstrated that PGF2α given in the IRF or IM in the neck resulted in similar rates of luteolysis (2002). However, Chebel et al found a difference in time to estrus in beef heifers given a prostaglandin analog either IM in the neck or subcutaneously (2007). The objective of this study was to determine if PGF2α given in the IRF results in luteolysis at a similar time as PGF2α given IM in the neck. Our goal is to provide producers and veterinarians with an alternative to the current practice of harmful injections in the rear legs.