Crossbred calves production under tropical conditions after direct transfer of cryopreserved in vitro fertilized embryos

HERNANDEZ-FONSECA, H. J.; SIRISATHIEN, S; SOTO-BELLOSO, E.; VELARDE, J. C.; GONZALEZ, R.; BOSCH, P.; LOTT, J. D.; BRACKETT, B. G.

Athens, Georgia, USA

Jornada; Veterinary Research Day; 2002

To assess feasibility for Bos taurus x Bos indicus production in Venezuela bovine embryos were produced by in vitro fertilization (IVF) at UGA under completely defined conditions with or without Leukemia Inhibitory Factor (LIF) and cryopreserved for direct embryo transfer (ET) into native Venezuelan heifers. Slaughterhouse-derived Bos taurus oocytes were matured 24 h, fertilized with frozen-thawed Brahman (Bos indicus) spermatozoa and cultured under completely defined conditions with or without LIF (100 ng/ mL). Resulting blastocysts were loaded into straws, precooled to -7 °C. After 10 min at -7 °C straws were cooled further to -30 °C at a rate of 0.3 °C/min and then plunged into liquid nitrogen (LN). Frozen embryos were sent to Venezuela in either LN vapor (-150 °C) or submerged in LN (-196 °C). ETs were performed early or late in the day to avoid conditions of highest humidity and heat. Each recipient received one embryo in the horn ipsilateral to the corpus luteum. Pregnancies were diagnosed by rectal palpation 60 days after ET. A higher pregnancy rate resulted after transport in LN (14/98, 14.3% vs 3/67, 4.5% after transport in LN vapor). Data resulting from embryos transported only in LN revealed pregnancy outcome was not improved by LIF treatment (5/51, 9.8% vs 9/47, 19.2% for controls). Of these 14 pregnancies 6 were lost; (3 aborted, one recipient died from snake bite and 2 stillbirths). Eight healthy calves were born avg. (37.1 Kgs avg. wt.). Recently, an increase in pregnancy initiation per ET recipient followed transfer of 2 embryos, produced in chemically defined (6/16, 37.5%) or in serum-containing media (8/17, 47%). Data document feasibility for producing crossbred cattle in the tropics via our U.S.-Venezuela collaboration. (Supported by UGA ASRT-5; VIATECA, Venezuela; Santa Elena Ranch, Madisonville, TX and Brown Packing Co., Gaffney, SC).