Effect of age of donor on embryo production in Morada Nova (white variety) ewes participating in a conservation programme in Brazil.

In order to evaluate embryo production in Morada Nova (white variety) ewes superovulated with porcine follicle-stimulating hormone, 20 cycling ewes were used as embryo donors and allocated into two groups according to age: group 1 (ewes aged 1-2 years; n = 9) or group 2 (ewes aged 3-4 years; n = 11). Embryo recovery was performed by laparotomy 5-6 days after oestrus. The evaluation of embryos was made under stereomicroscope according to International Embryo Transfer Society rules. The overall recovery rate was 64.6% (5.0 +/- 0.7 structures per ewe) and 86.3% of the recovered structures were fertilized. Group 1 was superior (p < 0.05) to group 2 according to recovered (6.6 +/- 0.9 vs 3.6 +/- 0.8) and fertilized structures (5.6 +/- 1.1 vs. 3.5 +/- 0.7) per ewe. In conclusion, the ovarian response and the embryo production in Morada Nova (white variety) sheep subjected to a standard superovulation treatment were considered satisfactory. In addition, the use of multiple ovulation and embryo transfer in younger ewes ( < or = 2 years old) of this sheep breed appears to be an efficient tool to accelerate the preservation of the Morada Nova (white variety) breed, since younger ewes are as responsive as older ones.

Duração da gestação e do parto em éguas Puro Sangue Arabe / Length of gestation and parturition in Arabian Thoroughbred mares

The length of gestation and parturition in 147 Arabian Thoroughbred mares were studied. Length of gestation averaged 330 days and was influenced by the age of mare. They were 335, 330 and 328 days for mares aged up to 4 years, 5 to 9 years and over 10 years, respectively. Parturition lasted 56 minutes on average and was not influenced by the reproductive condition of the mare. Most births occurred at night.