Consequences of varying methionine concentrations on development of the bovine embryo in vitro†

Methionine is an essential amino acid that influences key cellular processes. This study examined how methionine concentrations representing deficiency (0 μM), estimated uterine concentration in cows (31 μM), and a supra-physiological concentration (i.e., rumen-protected methionine; 57 μM) affect bovine preimplantation embryo development. When compared to 31 and 57 μM methionine, methionine deficiency (0 μM) reduced the percentage of zygotes developing into blastocysts by day 7.5 and the proportion of blastocysts that hatched at day 7.5, 8.5, and 9.5. Blastocysts produced without methionine developed slowly, had fewer total, CDX2+ (trophectoderm), and SOX2+ (inner cell mass) cells, and exhibited higher apoptosis and lipid content. Increasing methionine from 31 to 57 μM did not improve blastocyst development or hatching but increased CDX2+ cell number and reduced apoptosis and lipid content. Methionine concentration had no effect on survival to vitrification. In conclusion, the absence of methionine reduces the competence of zygotes to become a blastocyst and has detrimental effects on the properties of those blastocysts. A higher methionine concentration increases trophectoderm cell number, reduces apoptosis, and lowers lipid accumulation. These findings suggest that nutritional strategies to increase methionine availability during the periconceptional period may enhance blastocyst competence for continued development.