Route of prostaglandin F2alpha injection and luteolysis in mares (38519).

This research is a comparative analysis of the efficacy of the route and dosage of prostaglandin F2alpha (PGF-2alpha) injections on luteolysis in mares. The results indicated no significant changes in the effects with route but notable variations with dosage adjustments.

Experimental Design

• The experiment involved nine groups of pony mares, with three in each group. It was designed as a 3 x 3 factorial experiment, evaluating two main factors:
• PGF-2alpha dosage, which varied across three levels: 0, 0.25 and 1.25 mg; and
• The route of drug administration, comprising intramuscular (im), intrauterine (iu), or intra-luminal (il) injections.
• The mares underwent laparotomy and treatment on day seven post-ovulation. Jugular blood samples were taken before and at various intervals after treatment.
• The central goal was to see how different dosages and administration routes affected progesterone concentration over time after PGF-2alpha administration. The study also evaluated the interval from treatment to estrus or ovulation, the length of posttreatment estrus, and the length of the interovulatory interval.

Experimental Findings

• Both 0.25 mg and 1.25 mg doses of PGF-2alpha had similar influences among the three administration routes, save for the 6-hr mark post-treatment.
• At the 6-hr mark, progesterone levels were notably lower for mares injected intramuscularly than intrauterinely with the 0.25 mg dose.
• Compared to pretreatment progesterone values, administering PGF-2alpha led to significant progesterone concentration reduction by 12 hrs posttreatment in intramuscularly injected mares and 24 hrs in intrauterinely or intra-luminally injected mares.
• In the intrauterine group specifically, progesterone concentration increased significantly between the 1hr and 6hr marks followed by a significant decrease at 12 hrs post-treatment.
• No significant differences were recorded among the three routes regarding the intervals from treatment to estrus or ovulation, the length of posttreatment estrus or the interovulatory interval duration.
• Both 0.25 mg and 1.25 mg PGF-2alpha injections significantly reduced the interval from treatment to estrus. The 1.25 mg dose was more successful in significantly shortening the interval from treatment to ovulation and the interovulatory interval.
• The study concludes that the luteolytic efficacy of PGF-2alpha is not improved by local administration (iu or il) over systemic administration (im).