A simple salt solution medium supplemented with yolk plasma and lactate (YPLM) supports development of preimplantation bovine embryos in vitro

This study investigated the embryotropic potential(s) of egg yolk (EY) or i ts fractions, yolk plasma (YP) and yolk granules (YG), in culturing bovine embryos in vitro and substituting for protein (FCS, BSA, and BME-E and MEM- NE amino acids) and energy (glutamine, pyruvate and L-lactate) supplements commonly added to culture medium. In the first set of experiments (Experime nt 1, 2 and 3) CR1aa with buffalo rat liver (BRL) cells were used as a co-c ulture system. The addition of 2.5% or 5% EY significantly increased (P < 0 .05) blastocyst percent over the BRL control (48.3% and 52.4% vs. 32.5%, re spectively). The addition of 5% EY in the absence of FCS and BSA resulted i n percent development to blastocysts and hatched blastocysts similar (P > 0 .05) to those of the BRL control (37.6% and 57.4% vs. 51.5%, 22.7% and 39.5 %, respectively). The supplementation of the BRL control with 5% YP compare d to that of EY resulted in comparable (P > 0.05) percentages of blastocyst s and hatched blastocysts (39.0% and 51.6% vs. 40.0% and 58.3%, respectivel y). In the second set of experiments, the embryotropic potential of YP was examined using a cell-free culture system and a simple salt solution (SS) o f NaCl, KCl and NaHCO3 as the base medium. The supplementation of an energy -supplemented cell-free simple salt solution (E-SS) with 5% YP in the absen ce of supplemental protein resulted in percent development into blastocysts and hatched blastocysts comparable(P > 0.05) to those of a BRL control (39 .2% and 15.8% vs. 37.1% and 22.2%, respectively). The addition of YP to the simple salt solution with hemicalcium L-lactate as the only supplemented e nergy ingredient resulted in percentages of blastocysts and hatched blastoc ysts similar (P > 0.05) to those obtained by the supplementation of all ene rgy sources (27.4% and 15.6% vs. 36.4% and 14.0%, respectively). Increasing hemicalcium L-lactate level from 5 to 10, 20 or 25 mM resulted in a signif icant decrease (P < 0.05) in percent development into blastocysts (36.5% vs . 24.8%, 11.6% and 6.7%, respectively). In conclusion, YP, with the advanta ge of being clearer than EY, is capable of sustaining embryo development to the blastocyst stage in a simple salt solution of NaCl, KCl and NaHCO3 sup plemented with hemicalcium L-lactate. (C) 1999 Elsevier Science B.V. All ri ghts reserved.