Amino acid concentrations in fluids from the bovine oviduct and uterus and in KSOM-based culture media.

Amino acids in bovine oviductal and uterine fluids were measured and compared with those in modified simplex optimized medium (KSOM) supplemented with either fetal calf serum or Minimum Essential Medium amino acids in addition to bovine serum albumin, fetal calf serum or polyvinyl alcohol. Concentrations of cysteine, threonine, tryptophan, alanine, aspartate, glycine, glutamate, proline, beta-alanine, and citrulline were higher in oviductal fluids than in KSOM-based culture media. Nonessential and essential amino acids were present in ratios of 5:1 and 2:1 in oviductal and uterine fluids, respectively. Concentrations of alanine (3.7 mM), glycine (14.1 mM) and glutamate (5.5 mM) were high in oviductal fluids, comprising 73% of the free amino acid pool. Of the amino acids measured in uterine fluids, alanine (3.1 mM), glycine (12.0 mM), glutamate (4.2 mM), and serine (2.7 mM) were highest in concentration, and the first three comprised 43% of the free amino acid pool. In conclusion, amino acid concentrations in the bovine reproductive tract were substantially higher than those in embryo culture media. Certain amino acids, particularly alanine, glutamate, glycine and taurine, are present in strikingly high concentrations in both oviductal and uterine fluids, suggesting that they might play important roles in early embryo development. The particular pattern of amino acid concentrations may be an important factor to be considered for the improvement of embryo culture media.

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 its 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 (Experiment 1, 2 and 3) CR1aa with buffalo rat liver (BRL) cells were used as a co-culture 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%, respectively). The addition of 5% EY in the absence of FCS and BSA resulted in 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 compared to that of EY resulted in comparable (P>0.05) percentages of blastocysts and hatched blastocysts (39.0% and 51.6% vs. 40.0% and 58.3%, respectively). 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) of 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 absence 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 energy ingredient resulted in percentages of blastocysts and hatched blastocysts similar (P>0.05) to those obtained by the supplementation of all energy 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 significant 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 advantage 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 supplemented with hemicalcium L-lactate.