A major use of prostaglandin is to manipulate mares' estrous cycles. A veterinarian's most commonly used prostaglandin treatments are usually Lutalyse (dinoprost tromethamine or PGF2) and the prostaglandin analogue (a similar compound) Estrumate (cloprostenol or CLO). Some side effects observed when mares are treated with labeled doses of these medications include sweating and colic, and as a result owner distaste for using the drugs is growing.

Gary J. Nie, DVM, PhD, consultant for World Wide Veterinary Consultants, LLC in Rochester, Minn., conducted a study while at Auburn University where he compared "micro" doses of both products with standard doses for their ability to affect luteolysis and short-cycle mares.  He also evaluated the ability of microdoses to reduce side effects observed with standard doses.

Nie found that a microdose of CLO is equally as effective at short-cycling mares as standard doses of PGF2 or CLO, yet it virtually eliminates unwanted side effects and reduces drug costs by 1,000-2,000%.  He does not recommend a single microdose of PGF2, however, because of a delayed progesterone drop observed in the treated mares.

Prostaglandin's function in this case is to lyse the progesterone-producing corpus luteum left after ovulation, and return the mare to estrus. Thus, a progesterone drop is indicative of prostaglandin efficacy