Medroxyprogesterone priming and response to the ram effect in Corriedale ewes during the nonbreeding season.
The "ram effect" (RE) is an inexpensive technique that allows farmers to obtain out-of-season lambs. Five hundred and ninety-six Corriedale ewes were used in three experiments to determine the effectiveness of different medroxyprogesterone (MAP) treatments associated with the ram effect during the nonbreeding season. The aim of the first experiment was to evaluate the effectiveness of short-term (6-day) MAP priming. We obtained similar results in estrus incidence and fertility after using MAP sponges for 6, 9, and 13 days. In the second experiment, we compared the effect of sponges containing 20, 40, or 60 mg of MAP used in 6-day priming. Estrous behavior and fertility were not affected by dosage. In the third experiment, 2.5mg of MAP was administered in single treatments 0, 1, 3, or 5 days before the introduction of the rams. Medroxyprogesterone administration 1, 3, or 5 days before the introduction of the rams concentrated estrus in ewes 17 to 20 days later.
Ungerfeld
Rodolfo
R
Departamento de Fisiología, Facultad de Veterinaria, Lasplaces 1550, Montevideo 11600, Uruguay. piub@internet.com.ny
Suárez
Gonzalo
G
Carbajal
Bettina
B
Silva
Leticia
L
Laca
Mariana
M
Forsberg
Mats
M
Rubianes
Edgardo
E
D000818:Animals; D001947:Breeding / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005298:Fertility / Q000187:drug effects*; D008297:Male; D008525:Medroxyprogesterone / Q000494:pharmacology*; D045167:Progesterone Congeners / Q000494:pharmacology*; D012621:Seasons; D012756:Sheep / Q000502:physiology*; D013997:Time Factors
D045167:Progesterone Congeners; D008525:Medroxyprogesterone