164 EFFECT OF ACCUMULATION OF LIPIDS DURING IN VITRO CULTURE ON BOVINE BLASTOCYST YIELD AND FETAL DEVELOPMENT

Abstract

Previous research has shown that increased embryo lipid content, through culture in the presence of serum, is associated with reduced blastocyst yield and quality; provision of antioxidants ameliorates the effects of lipid accumulation (McEvoy et al. Reprod. Fertil. Dev. 16, 200). The present study extended these observations to assessment of fetal development from blastocysts which had accumulated lipid in vitro. Bovine oocytes, aspirated from abattoir-derived ovaries, were matured and fertilized using standard procedures. Cleaved zygotes were assigned to culture (5% CO2; 5% O2; 90% N2; 38.5°C) in four treatments: (1) synthetic oviductal fluid containing 0.3% bovine serum albumin and amino acids (SOF); (2) SOF plus supplementary bovine lipoproteins (2%, SOFLP); (3) SOF plus the antioxidant Trolox® (100 μM; 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid, Sigma-Aldrich Co., Inc., Irvine, UK; SOFT); and (4) SOF plus lipoproteins and Trolox (SOFLPT). Blastocysts were synchronously transferred to recipient cattle (day 7; 23/treatment) together with a control group (n = 21) of artificially inseminated (AI) cattle. Reproductive tracts were recovered on Day 70 and fetal total and organ weights recorded. Data were analyzed by ANOVA (with fetal sex as covariate) and chi-square analyses. Culture in the presence of lipoproteins increased blastocyst total fatty acids (mean ± SD) from 98 ± 9.7 to 124 ± 7.3 ng/blastocyst. Blastocyst yields (%; 23 batches of ovaries) were reduced (P = 0.002) by inclusion of lipoproteins in culture (SOF, 22.0 ± 8.20; SOFLP, 16.4 ± 8.57; SOFT, 22.8 ± 9.03; SOFLPT, 24.2 ± 7.30) unless Trolox was present. Blastocyst grade was poorer (P < 0.001) after culture in the presence of lipoproteins irrespective of the presence of Trolox (SOF, 2.4 ± 0.43; SOFLP, 2.6 ± 0.45; SOFT, 2.4 ± 0.47; SOFLPT, 2.6 ± 0.40). Pregnancy rates (Day 70) were greater (P < 0.001) for AI (91%) than culture (26%) but were not affected by culture treatment. Although there were no differences in fetal weights between AI and IVC fetuses, SOFLP fetuses (Table 1) were lighter, had smaller relative liver weights, and had greater crown-rump length-to-weight ratios than other IVC fetuses. Therefore, IVC in conditions that increased blastocyst lipid content without adequate antioxidant protection reduced blastocyst yield and influenced fetal development. Table 1. Fetal weights (g) and relative liver weights (g/kg) and crown-rump lengths (CRL, mm/g) at day 70 SAC receives financial support from SEERAD.