EFFECT OF PROSTAGLANDIN-F2-ALPHA DOSAGE AND ROUTE OF ADMINISTRATION ON ESTRUS RESPONSE IN CRIOLLO GOATS UNDER RANGE CONDITIONS

Criollo goats (n = 276) of various ages and kept under range condition were used to determine the influence of prostaglandin F2 alpha (PGF2 alpha) dosage and route of administration on proportion of does showin g estrus and interval to estrus. Goats were randomly assigned to 12 tr eatments in a 6 x 2 factorial arrangement. Treatments were 6, 4, 2, 1. 5, 1 and 0.5 mg PGF2 alpha per animal, administered either intramuscul ar (i.m.) or intravulvo-submucosa (i.v.s.m.) in November. Two injectio ns of PGF2 alpha were administered to goats 11 d apart. Goats were obs erved twice daily for signs of behavioral estrus over 3 d. Percentage of goats exhibiting estrus within 24 h following the second applicatio n of prostaglandin was higher (P<0.01) for goats injected i.v.s.m. tha n those injected i.m. The proportion of does showing estrus was depend ent upon dosage of PGF2 alpha (P<0.01), but not upon route of administ ration. Goats injected with 6 and 4 mg of PGF2alpha responded similarl y (range = 55-68%, independent of route of administration). Response t o 2 mg of PGF2alpha was intermediate between higher and lower doses. O nly around 25% of goats responded to 1.5, 1.0 or 0.5 mg PGF2alpha, wit h minimal variation among these doses. Independent of the route used ( i.m. or i.v.s.m.), 4 mg of PGF2alpha was the minimal dose efficient fo r induction of estrus in the Criollo goats.