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One-cell cattle embryos were prepared by in vitro oocyte maturation and fertilization (IVM/IVF) and cultured with or without oviductal cells. Embryos were evaluated after 7 days in culture to determine the percentage developing from the 1-cell stage to the morula or blastocyst stage. The combination of glycine (2 mM) and alanine (1 mM) with oviductal cells (experiment 1) improved embryo development over that in control culture (29 vs. 13%; p < 0.05). An optimum response was obtained with 10 mM glycine and 1 mM alanine in coculture (experiments 2 and 3). In experiment 4, the effects of glycine (0 or 10 mM), alanine (0 or 1 mM), and the presence or absence of oviductal cells were tested. In the absence of oviductal cells, the addition of glycine, alanine, or glycine and alanine combined improved embryonic development over that in control medium (45, 33, 42 vs. 24%, p < 0.001, p < 0.05, p < 0.001, respectively). However, the effect of the combination of glycine and alanine was not different from that of glycine alone when oviductal cells were absent (42 vs. 45%, p > 0.10). In the presence of oviductal cells, glycine or the combination of glycine and alanine improved embryonic development over that in the control medium with cells (47, 55 vs. 37%, p < 0.01, respectively). However, supplementation with alanine alone gave no improvement over controls when oviductal cells were present (40 vs. 37%, p > 0.10). These results indicate that glycine and alanine, when used independently, directly affect cattle embryo development, but in combination affect embryo development indirectly, possibly by altering oviductal cell function. Finally, oviductal cell-conditioned (48 h or 6 days) medium excluding glycine and alanine supplements was analyzed for free amino acids. Glycine and alanine were secreted by oviductal cells, suggesting that enhanced embryonic development achieved through coculture may be due, in part, to these amino acids.

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Biology of Reproduction

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