Effects of supplemental progesterone on the development, metabolism and blastocyst cell number of bovine embryos produced in vitro

The objectives of the present experiment were to determine whether supplementation with progesterone (LO, 1 ngmL (1) or HI, 100 ngmL (1)) during either the first (Culture-1, Day 1 to 3) or second (Culture-2, Day 4 to 7) phase of culture of in vitro-produced embryos alters embryo development, embryo metabolism or blastocyst cell number. The percentage of oocytes that cleaved, the percentage of cleaved embryos that developed to the morula stage or greater, the blastocyst stage or greater or the hatched blastocyst stage were similar among treatments. Quantities of glucose metabolised per blastocyst per hour were similar, but when metabolic data was normalised for numbers of cells in each blastocyst, the LO treatment during Culture-2 metabolised more glucose (P = 0.03) compared with all other treatments. Embryos receiving LO progesterone tended to have greater (P = 0.085) metabolism of glucose compared with embryos receiving HI progesterone. Quantities of pyruvate oxidised per blastocyst per hour, and per cell, were similar among treatments. The number of cells per blastocyst in the control group was increased (P = 0.039) compared with cells in progesterone-treated groups. In conclusion, supplementation with progesterone during the culture of in vitro-produced embryos does not appear to improve embryo characteristics.