In vitro development and nutrient uptake by embryos derived from oocytes of pre-pubertal and adult cows.

The present study compared the developmental potential and uptake of nutrients by embryos from pre-pubertal and adult cows. Oocytes retrieved from ovaries of 5 to 7 month old calves and adult cows were matured and fertilized in vitro. Embryos were cultured in SOFaa to the blastocyst stage (7 days post-insemination). At successive stages of development, rates of glucose and pyruvate uptake were measured non-invasively by microfluorescence for individual embryos. Fertilization was equivalent in embryos from pre-pubertal and adult cows (P > 0.05), however development to blastocyst was significantly lower in embryos from pre-pubertal cows (9.8% versus 33.7%, respectively; P < 0.05). Total blastocyst cell number was not different between pre-pubertal and adult material (P > 0.05). Glucose uptake was exponential (pre-pubertal, r = 0.82; adult, r = 0. 82; P < 0.05), with an increase in uptake beyond the 8- to 16-cell stage. Glucose uptake was significantly lower in embryos from pre-pubertal cows at the 2- to 4-cell stages (1.5 versus 3.0 pmoles/embryo/hr; P < 0.05), but was equivalent to the adult cow at all other stages of development (P > 0.05). Pyruvate uptake was low until the blastocyst stage. Pyruvate uptake by embryos from pre-pubertal cows was significantly different to adult cows at the 1-cell stage (2.7 versus 4.6 pmoles/embryo/hr, respectively; P < 0. 05) and 2- to 4-cell stages (4.9 versus 3.6 pmoles/embryo/hr, respectively; P < 0.05). Pyruvate uptake was equivalent in the two groups in the later stages of development (P > 0.05). Perturbations in the uptake of nutrients by embryos from pre-pubertal cows were most likely due to the presence of a high proportion of developmentally incompetent embryos. Further, embryos from pre-pubertal cows that did develop to the blastocyst were as viable as blastocysts from adult cows with respect to nutrient uptakes and total cell number.