Embryo production by ovum pick up in unstimulated calves before and after puberty

摘要

Ovum pick-up (OPU) coupled with in vitro embryo production was used on 7 or 9 Holstein calves, aged 7-10 months at the start of the experiment. The oocytes were collected twice weekly during a 2-month period before puberty (June and July 1997 and 15March and 15 May 1998 for the 7 and 9 calves respectively) and a 1-month period after puberty. Oocytes were fertilized and co-cultured with cumulus cells in modified synthetic oviduct fluid (SOF) up to day 7 after insemination. Some day 7 blastocysts were vitrified and transferred to recipient heifers. An average of 3.8-6.8 follicles was punctured per OPU session; 1.9-3.1 oocytes were collected, of which >60% were of good quality. The number of punctured follicles and oocytes recovered varied between donors. The rate of blastocyst development was 19 and 27% for the first and second sets of calves respectively. An average of 5-11 (range 0-16) blastocysts per donor was produced over 2 months. Three normal calves were born from the transfer of 20 vitrified embryos. While no significant difference was observed for the first set of calves, a significant decrease in the number of punctured follicles was observed after puberty in the second set. There was a direct correlation between the number of folliclespunctured before and after puberty in the same animal. It is concluded that oocytes can be collected by repeated OPU in calves 7-10 months old without affecting their growth or the onset of puberty.