142 EFFECT OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR AND INSULIN-LIKE GROWTH FACTOR-1 ON DEVELOPMENT AND POST-TRANSFER SURVIVAL OF BOVINE EMBRYOS PRODUCED IN VITRO

Abstract

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multifunctional cytokine that has been implicated in the regulation of preimplantation embryonic development in several species. Insulin-like growth factor-1 (IGF-1) can increase the proportion of bovine embryos that develop to the blastocyst stage and increase embryo survival following transfer to heat-stressed, lactating dairy cows (Block J et al. 2003 J. Anim. Sci. 81, 1590–1602; Theriogenology 67, 1518–1529). The current objective was to test whether addition of GM-CSF and IGF-1 to culture medium enhances development and post-transfer survival of in vitro-produced bovine embryos. Holstein COC shipped overnight in a portable incubator in oocyte maturation medium were fertilized with X-chromosome selected sperm from Holstein bulls. X-selected sperm were used because females were preferred. Morulae and blastocysts were collected at Day 7 after insemination and transferred at Day 7 after ovulation to lactating dairy cows subjected to a modified OvSynch protocol. In Experiment 1, conducted from June 29 to August 31, embryos were cultured in KSOM-BE2 alone, KSOM-BE2 with 100 ng mL^–1 of Arg³-IGF-1 or KSOM-BE2 with 10 ng mL^–1 of recombinant BoGM-CSF. Treatments were added at Day 1 after insemination. As compared to control embryos (17 ± 2%), the percentage of cleaved embryos that became transferable morulae or blastocysts at Day 7 was increased (P < 0.05) by GM-CSF (25 ± 2%) but not by Arg³-IGF-1 (18 ± 2%). There was no significant effect of treatment on pregnancy rate at Day 30 to 35 [34% (n = 52), 35% (n = 51), and 43% (n = 55) for control, GM-CSF, and IGF-1, respectively] or calving rate (27, 35, and 40%) although values were numerically greater for cows receiving IGF-1 treated embryos. In experiment 2, conducted from September 7 to February 1, embryos were cultured in KSOM-BE2 alone, KSOM-BE2 with 100 ng mL^–1 Arg³-IGF-1 added at Day 1 after insemination, or KSOM-BE2 with 10 ng mL^–1 recombinant BoGM-CSF added at Day 5 after insemination. GM-CSF, but not IGF-1, increased the percentage of oocytes (P < 0.03) and the percentage of cleaved embryos (P = 0.05) that became transferable morulae or blastocysts at Day 7. The percentage of cleaved embryos becoming blastocysts was 14 ± 1% for GM-CSF, 14 ± 2% for Arg³-IGF-1 (P = 0.11), and 10 ± 1% for controls. Treatment with GM-CSF increased (P = 0.056) the percentage of cows pregnant at Day 30 to 35 [34% (n = 79), 43% (n = 107), and 27% (n = 44) for control, GM-CSF, and IGF-1, respectively]. Data on calving rate are currently being collected; to date, 86% of calves were female. Results indicate that embryo competence for post-transfer survival can be enhanced by treatment with GM-CSF at Day 5 after fertilization.

Research supported by USDA Grant 2006-55203-17390, BARD Grant US-3986-07 and the Southeast Milk Dairy Checkoff Program. B.L. was supported by a CAPES (Brazil)/Fulbright Fellowship.