Effects of superovulated heifer diet type and quantity on relative mRNA abundances and pyruvate metabolism in recovered embryos

This study investigated the effects of quantity and type of diet fed to sup erovulated donor heifers on molecular and metabolic indices of embryonic de velopment. These effects included the relative abundances of mRNAs for the alpha 1 subunit of Na/K-ATPase and the antioxidant enzyme Cu/Zn-SOD, as wel l as pyruvate utilization in bovine morulae and blastocysts developed in vi vo. Heifers were fed a daily ration of either grass silage and a citrus-bee t pulp-based concentrate or grass silage and a barley-based concentrate for 116 days, both at 3 kg per day or ad libitum. In embryos derived from heif ers fed the pulp-based diets, the relative abundances of the transcripts we re not affected by either day of collection or quantity of diet. In embryos derived from heifers fed the barley-based diets, the relative abundances o f the Na/K-ATPase transcripts were also not changed by these main effects, while the relative abundances of the Cu/Zn-SOD transcripts were affected by day of collection and by the quantity of diet. Pyruvate metabolism was aff ected by day of collection, and was significantly increased in day 8 embryo s compared with day 7 and day 6 embryos. Diet quantity did not affect pyruv ate utilization, whereas diet type did increase pyruvate metabolism in the barley group when compared with the pulp group. The results of this study s how for the first time that molecular and metabolic variations may exist in embryos derived in vivo and developed in donor heifers on nutritional regi mens differing in type and quantity. Differences in embryos collected on di fferent developmental days may be attributed to varying cell numbers. Alter ations in the relative abundances of the Cu/Zn-SOD transcripts and pyruvate metabolism caused by the quantity of diet fed to the donor animal were Lik ely to have been due to alterations in metabolic end products that accumula te in reproductive tract fluids, whereas differences in embryonic metabolis m caused by type of diet are related to the composition of the diet. These findings characterize embryos produced in vivo at the molecular level, indi cating that the molecular markers used in the present study can differentia te between populations of embryos produced under different nutritional regi mens and determine conditions conducive to the production of good quality e mbryos.