DEVELOPMENT OF BOVINE EMBRYOS IN-VITRO AS AFFECTED BY ENERGY SUBSTRATES

Simple media were developed to study the metabolic requirements of bov ine embryos up to Day 7 (Day 0 = day of oocyte aspiration) in vitro. E mbryos were derived from oocytes matured and fertilized in vitro. At 4 5 +/- 2 h post insemination, embryos (greater-than-or-equal-to 2 cells ) were randomly allotted to treatments. Examined in experiments 1 and 3 was the effect of pyruvate concentration in the presence of lactate. In the presence of lactate, pyruvate (0.2-5.0 mM) had no effect (p > 0.05) on the percentage of morulae or blastocysts. However, increasing the concentration of hemicalcium L-lactate from 5 mM to 10 mM decreas ed (p < 0.001) the percentage of embryos reaching the morula or blasto cyst stage (experiment 3). Neither magnesium sulfate (0.5 mM) nor EDTA (10 mM) improved embryo development when added to the medium CR1 (exp eriment 2). Increasing the calcium level to 5 mM or the lactate level to 10 mM had no effect (p > 0.05) on embryo development (experiment 4) . However, the interaction of adding calcium and lactate resulted in a decreased (p < 0.05) percentage of morulae. Determined in experiment 6 were the independent effects of pyruvate, lactate, and glucose on em bryo development in vitro. As pyruvate or lactate level was increased from 1 to 10 mM, the percentage of blastocysts was decreased (p < 0.05 ). These experiments indicate that adding pyruvate to a medium contain ing lactate is not necessary for development of bovine embryos in vitr o.