Abstract
Ninety-nine Holstein-Friesian heifers, 11 to 15 months in age, had superovulated with PMSG and PGF2α. Factors affecting superovulation, nonsurgical egg recovery and egg quality were examined.
Ninety (90.9%) of the heifers were in estrus within 2 days after the PGF2α treatment. Ninety-five heifers came into estrus, were subjected to AI, and were classified into four groups according to the CL (number of corpus luteum) estimated; 1-5 CL, 6-10 CL, 11-15 CL and 15<CL. Ten (10.5%) of the heifers had 1-5 CL, 29 (30.5%) presented 6-10 CL, 30 (31.6%) produced 11-15 CL and 26 (27.4%) were estimated as having 15<CL. There were no differences in the rates of superovulation or number of CL between heifers treated during the summer pasturing season and the winter housing season, nor were there differences in heifers 11-13 months and 14-15 months in age.
In 90 heifers nonsurgical recovery was performed between days 6 to 9 after estrus. It was not possible to pass a 16 FG Foley catheter or Sugie's 2-way apparatus through the cervix in 5 (5.3%) of 95 heifers. Eggs were collected in 82/90 (91.1%), averaging 7.3 per successful heifer and 6.6 per flushed. In 4 (4.9%) of 82 heifers only uncleavaged eggs were obtained. The number of eggs recovered tended to increase with the rate of superovulation.
The percentage of normal embryos, which showed no signs of degeneration or which were at the expected developmental stage according to estrus, decreased from days 6 to 7 (67.2% as against 53.5%; significant difference: P<0.05). Effects of the season at treatment, the age of the heifer and the rate of superovulation on the eggs recovered were not found.
