139 THE EFFECT OF STARCH AND SATURATED OR POLYUNSATURATED RICH DIETS ON IN VITRO BOVINE EMBRYO DEVELOPMENT AND QUALITY

Abstract

In humans, diets rich in carbohydrates and saturated fatty acids are common and the subsequent altered metabolism has been linked to reduced fertility. Also, modern dairy cows are fed milk-stimulating diets rich in starch and fatty acids. The pre-implantation embryo is vulnerable to nutritionally induced changes in its micro-environment. We have shown that a dietary induced hyperlipidemia has detrimental consequences on development, quality and gene expression patterns of the pre-implantation embryo (Leroy et al. 2010 Hum. Reprod. 25, 768–778). Hyperlipidemia was induced by feeding starch- and saturated-fat-rich diets and the collected serum was added during bovine embryo culture. In the present study, we hypothesized that changing the saturated into a polyunsaturated fat source could alleviate these negative effects. We furthermore hypothesized that the sequence in which the different fat sources are given can affect embryo development and quality. Therefore, in the first setup: bovine zygotes (n = 1104; 4 replicates) were cultured in SOF medium supplemented with 10% serum collected from 3 synchronized heifers after 3 successive dietary treatments each fed during 4 weeks: control serum after a hay-based maintenance diet, saturated serum (SAT1) after a carbohydrate rich diet supplemented with saturated fatty acids (twice maintenance, C16 : 0, palmitic acid, 4.5% total fat), or unsaturated serum (UNSAT1) after a carbohydrate-rich diet supplemented with unsaturated fatty acids (twice maintenance, C18 : 3, linolenic acid, 4.45% total fat). In the second setup (n = 1483; 5 replicates): bovine zygotes were cultured in SOF medium supplemented with 10% serum from 3 synchronized heifers successively fed the 3 same dietary treatments in different order: control, unsaturated (UNSAT2), or saturated serum (SAT2). Day 7 blastocyst developmental competence (binary logistic regression), total cell number, and apoptotic cell ratio (ACR) (mixed model ANOVA) were evaluated. Supplementation of SAT1 serum in culture significantly reduced blastocysts from cleaved zygotes (36.7% v. 44.7%) and significantly increased ACR (0.1% ± 0.05 v. 0.06% ± 0.04) compared to controls (P < 0.05). Zygotes cultured in UNSAT1 displayed a significant higher cell number than control and SAT1 blastocysts (126.4 ± 25.7 v. 120.4 ± 24.3 and 108.3 ± 15.5, respectively; P ≤ 0.05) and lower ACR compared to SAT1 blastocysts (0.06% ± 0.03 v. 0.1% ± 0.05; P < 0.05). However, UNSAT1 zygotes showed a tendency for reduced development into blastocysts compared to control zygotes (P = 0.05). By contrast, UNSAT2 serum significantly improved blastocysts development from cleaved zygotes (40.0% v. 26.7%) and led to a lower ACR (0.06% ± 0.04 v. 0.1% ± 0.05) compared to SAT2 embryos (P < 0.05). In conclusion, our study confirmed the negative effects diets rich in starch and saturated fat on pre-implantation embryo development and quality. Changing the fat source to polyunsaturated eliminated these negative effects. Furthermore, we showed that the order in which different fat types are fed affects the zygote’s ability to sustain further development.