Influence of climatic conditions on in vitro production of bovine embryos

Temperature and rainfall were analyzed daily during six years to evaluate their influence on in vitro production of bovine embryos. Weekly replications (n=480) were performed on 14,778 ovaries collected at slaughterhouses. Cumulus oocyte complexes (n=19,180) were fertilized with a pool of Bos taurus taurus semen in one incubator with 5% CO2. Presumable zygotes were cultured in gasified plastic bags with 5% CO2, 5% O2, and 90% N2. In the first year, cleavage and embryo yield were 60.3% and 15.6%, respectively, being lower (P<0.05) than in the following years. Average cleavage rates were always lower in winter (P<0.0001), thus producing less embryos. Winter climatic conditions had a negative influence on in vitro production, when cleavage and embryo yield declined, possibly because of reduced availability and growth of native pasture.