Use of insulin-like growth factor-I during embryo culture and treatment of recipients with gonadotropin-releasing hormone to increase pregnancy rates following the transfer of in vitro-produced embryos to heat-stressed, lactating cows.
An experiment was conducted to determine whether pregnancy rates following the transfer of in vitro-produced embryos to heat-stressed cows could be improved by 1) culturing embryos in the presence of IGF-I and 2) treating recipients with GnRH. Lactating Holstein cows (n = 260) were synchronized using a timed ovulation protocol. Embryos were produced in vitro and cultured with or without 100 ng/mL of IGF-I. On d 7 after anticipated ovulation (d 0), a single embryo was transferred to all recipients with a palpable corpus luteum (n = 210). A subset of recipients (n = 164) was injected with either GnRH or placebo on d 11. Plasma progesterone concentrations on d 0 and 7 were used to determine the synchrony of recipients. Pregnancy was diagnosed at d 53 and 81 by rectal palpation. Among all recipients, transfer of IGF-I-treated embryos increased pregnancy rate at d 53 (P < 0.05) and tended to increase pregnancy rate at d 81 (P < 0.06). Calving rate also tended to be higher for recipients that received IGF-I-treated embryos (P < 0.07). Among the subset of synchronized recipients (n = 190), pregnancy rate at d 53 and d 81 and calving rate were higher (P < 0.05) for IGF-I-treated embryos. The GnRH tended to increase pregnancy rate at d 53 for all recipients (P < 0.08) and the subset of synchronized recipients (P < 0.10). There were no effects of GnRH (P > 0.10) for pregnancy rate at d 81 and calving rate. The overall proportion of male calves was 64.3%. There was no effect (P > 0.10) of embryo treatment or GnRH on the birth weight or sex ratio of calves. Results of this experiment indicate that treatment of embryos with IGF-I can improve pregnancy and calving rates following transfer of in vitro-produced embryos. Further research is necessary to determine whether the treatment of recipients with GnRH is a practical approach to increase pregnancy rates following in vitro embryo transfer.
Block
J
J
Department of Animal Sciences, University of Florida, Gainesville 32611, USA.
Drost
M
M
Monson
R L
RL
Rutledge
J J
JJ
Rivera
R M
RM
Paula-Lopes
F F
FF
Ocon
O M
OM
Krininger
C E
CE
Liu
J
J
Hansen
P J
PJ
D000818:Animals; D001724:Birth Weight / Q000187:drug effects; D002417:Cattle / Q000196:embryology / Q000502:physiology*; D003470:Culture Media; D004624:Embryo Transfer / Q000662:veterinary*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D006358:Hot Temperature; D007315:Insemination, Artificial / Q000662:veterinary; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage*; D007774:Lactation; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000097:blood; D012744:Sex Ratio; D013997:Time Factors
D003470:Culture Media; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D007334:Insulin-Like Growth Factor I