Exogenous growth hormone improves the number of transferable embryos in superovulated ewes

The application of pGH (porcine Growth Hormone) to superovulated ewes was s tudied with the aim of improving the embryo yield. Thirty-seven ewes were s uperovulated with pFSH for 3 d and 18 of them were cotreated the third day with 0.50 mg of pGH. Embryos were surgically recovered on Day 7 after spong e withdrawal. Then, 102 morphologically healthy embryos were immediately tr ansferred in pairs to 51 synchronized recipient ewes. The GH treatment did not significantly affect the percentage of ewes in estrus, the time of estr us onset or the ovulation rate. However, it improved synchronization by gro uping estrus in a narrower range (12 h) in comparison to the control group (24 h); (16 to 28 h after sponge withdrawal vs 12 to 36 h; P < 0.05). The t otal amount of LH released during the preovulatory surge was lower in the G H than in the control group (P < 0.05). No differences were found between g roups for other LH-related parameters such as basal levels, peak values or peak time from sponge removal. The proportions of unfertilized oocytes and degenerate embryos recovered were lower in the GH cotreated group (P < 0.05 and P < 0.01, respectively). This resulted in higher rates of transferable embryos and lambs born per donor ewe in the GH than in the untreated group (3.9 vs 1.7 and 2.28 vs 0.84, respectively; both, P < 0.05). These benefic ial effects of GH would likely be due either to a direct action on oocyte m aturation or to an indirect action on the oviductal environment. (C) 2001 b y Elsevier Science Inc.