122 EFFECTS OF EMBRYO SEX AND GLUCOSE OR FRUCTOSE IN CULTURE MEDIA ON BOVINE EMBRYO DEVELOPMENT

Abstract

The objective of the present study was to determine if glucose, fructose, or both, in culture medium affects female embryos differently from male embryos. Embryos of predetermined sex were produced by use of sexed semen. Blastocysts were produced in vitro in a factorial design from 1851 oocytes fertilized with 3 sperm types [non-sexed control, X-bearing, and Y-bearing (~95% accuracy)]. Semen from 3 bulls (A, B, and C) was used, with 2 replicates for each bull. Zygotes were cultured with 4 energy substrates (no-hexose control, glucose, fructose, and glucose + fructose). Chemically defined medium (CDM) plus 0.5% fatty acid-free BSA (De La Torre-Sanchez et al. 2006 Mol. Reprod. Dev. 18, 585–596) was the culture medium to which the energy substrates were added. For the first 2.5 d of culture, the medium contained 0.5 mm hexose, and for the last 4.5 d, it contained 2.0 mm hexose. Data were analyzed by ANOVA. There was no effect of hexose treatments on cleavage rates (P > 0.1; Table 1). However, blastocyst rates per oocyte were higher for the fructose treatment than for the control, glucose, or glucose + fructose (P < 0.05) groups. Glucose treatment resulted in retarded development compared with no hexose or fructose (P < 0.05). Analysis of a subset of data with only the fructose and glucose treatments resulted in an interaction of hexose (glucose and fructose) and X-bearing andY-bearing sperm for blastocysts per oocyte: fructose X-sperm 20.4%^a; fructoseY-sperm 17.7%^ab; glucose X-sperm 10.6%^bc, and glucoseY-sperm 14.7%^c (means without common superscripts differ; P < 0.05). Glucose was detrimental to female embryos, and fructose improved development to the blastocyst stage for both sexes. Lower cleavage rates were found after fertilization with X-bearing sperm (Table 1); however, blastocyst rates per oocyte were not different after fertilization with X- or Y-bearing sperm or non-sexed sperm (P > 0.1). There was no bull effect on rates of cleavage or blastocysts per oocyte (P > 0.1). In conclusion, fructose improved embryonic development of embryos of both sexes; glucose retarded development of, and was toxic to, female embryos. Sexed sperm resulted in similar cleavage and blastocyst production as non-sexed sperm, and female embryos had retarded embryonic development relative to male embryos.

Table 1. Main effect least-squares means for development of bovine embryos (±SE)