Effect of exogenous carbohydrates in a serum-free culture medium on the development of in vitro matured and fertilized porcine embryos

This study was conducted to examine the effect of energy substrates in a serum-free culture medium on in vitro development of porcine embryos. Presumptive zygotes derived from in vitro fertilization were cultured in glucose-free North Carolina State University (NCSU)-23 medium with glucose, pyruvate, fructose and lactate added to the culture medium singly or in various combinations. In experiment 1, a higher percentage of embryos cleaved (53–63% vs 10–13%) and developed to the blastocyst stage (18–27% vs 0) after the single addition of glucose (5.6 mM), pyruvate (0.5 mM) or lactate (10 mM) than with no energy substrate addition or the addition only of fructose (5.6 mM). In experiment 2, the addition of pyruvate and lactate resulted in higher blastocyst formation (25%) than other combinations (6–22%), while the addition of glucose and pyruvate significantly inhibited blastocyst formation. Increasing lactate concentration, as a single energy supplement, from 5 to 20 mM significantly improved blastocyst formation (7% vs 14–18%), while no benefit was achieved from increasing pyruvate concentration up to 2 mM (experiment 3). Glucose-free NCSU-23 medium supplemented with 0.5 mM pyruvate and 5 mM lactate significantly improved blastocyst formation (28% vs 17%) compared with NCSU-23 medium supplemented with 5.6 mM glucose (experiment 4). In conclusion, pyruvate and lactate are preferable energy substrates to support in vitro development of porcine embryos cultured in a serum-free NCSU-23 medium.