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

The possibility of producing embryos from oocytes repeatedly collected from unstimulated calves was rested,and results obtained before and after puber ty were compared in the same animals. Ovum pick-up (OPU) coupled with in vi tro embryo production was used on 2 sets of 7 and 9 calves, aged 7 to 10 mo at the start of the experiment. The oocytes were collected twice a week du ring a 2-mo period before puberty and a 1-mo period after puberty. Oocytes were fertilized and co-cultured with cumulus cells in modified synthetic ov iduct fluid (SOF) up to Day 7 post insemination. Some Day 7 blastocysts wer e vitrified and transferred to recipient heifers. An average of 3.8 to 6.8 follicles was punctured per OPU session; 1.9 to 3. 1 oocytes were collected, of which more than 60% were of good quality. The number of punctured follicles and collected oocytes varied between donors. Blastocyst rates of 19 to 27% were obtained for the 2 sets. Three normal ca lves were born from the transfer of 20 vitrified embryos. While no signific ant difference was observed for the first set of calves, a significant decr ease in the number of punctured follicles was observed after puberty in the second set. A direct correlation was also obtained between the number of f ollicles punctured before and after puberty in the same animal. In conclusi on, oocytes can be collected by repeated OPU in calves 7 to 10 mo old witho ut affecting their growth or the onset of puberty. An average of 5 to 11 (r ange 0 to 16) blastocysts per donor was produced over 2 month. However, imp ortant variations were Pound between donors. The correlation observed for t he number of follicles punctured before and after puberty suggests that thi s parameter is determined before puberty. (C) 1999 by Elsevier Science Inc.