Abstract
Here we assessed the effects of dietary essential fatty acids on the developmental competence of oocytes in cows and on the functionality of follicular granulosa cells (GC). Lactating German Holstein cows were supplemented from week 9 ante partum (ap) until week 8 post-partum (pp) in four dietary groups designed as (i) control (CTRL: coconut oil), (ii) essential fatty acid (EFA: linseed and safflower oil), (iii) conjugated linoleic acid (CLA: Lutalin®), and (iv) EFA+CLA (mixture of linseed oil, safflower oil and Lutalin®). EFA, CLA or EFA+CLA supplementation did not improve in vitro embryo production. However, higher proportions of α-linolenic acid (ALA) and cis-9, trans-11 CLA were observed in the follicular fluid suggesting the exposure of GC to relatively high levels of ALA and cis-9, trans-11 CLA. Consequently, we tested different concentrations of ALA and cis-9, trans-11 CLA in a bovine GC culture model for their effects on steroid production, marker gene expression and viability. Both fatty acids upregulated CD36 and downregulated the expression of FOXL2, while ALA significantly increased SOX 9 transcript levels. Both ALA and cis-9, trans-11 CLA reduced the CCND2 expression and cis-9, trans-11 CLA induced apoptosis. ALA and cis-9, trans-11 CLA significantly down-regulated the expression of STAR, CYP19A1, FSHR, LHCGR and decreased the 17β-Estradiol (E2) and progesterone (P4) production. In conclusion, dietary lipids did not improve in vitro embryo production, while ALA and cis-9, trans-11 CLA affected the morphology and functionality of GC. This could suggestively lead to compromised follicle development and ovarian cyclicity in dairy cows.
Highlights
Dietary supplements can improve the reproductive outcome in cows by increasing the energy intake reducing the extent of negative energy balance (NEB) experienced postpartum [1]
Due to higher proportions of ALA and cis-9, trans-11 conjugated linoleic acid (CLA) in follicular fluid (FF), we speculate that granulosa cells (GC) are exposed to relatively high levels of ALA and cis-9, trans-11 CLA which might affect the functionality of GC residing within
As expected we observed a higher percentage of ALA in the FF of essential fatty acid (EFA) and EFA + CLA diet fed cows, while the percentage of the cis-9, trans-11 CLA was higher in the FF of CLA and EFA+CLA diet fed cows as compared to the CTRL diet fed cows
Summary
Dietary supplements can improve the reproductive outcome in cows by increasing the energy intake reducing the extent of negative energy balance (NEB) experienced postpartum [1]. Polyunsaturated fatty acids (PUFA) enriched diets in cattle are known to alleviate NEB during early lactation [2]. Ewes fed with PUFA diets showed higher proportions of LA and docosahexaenoic acid (DHA) in FF and cumulus cells with lower proportions in oocytes [7]. The size of dominant follicles is reported to increase in cows fed with PUFA diets as compared to cows fed with monounsaturated fatty acids (MUFA) [8]. Dietary effects of essential fatty acids ALA and CLA or their mixture on oocyte developmental competence as well as their effects on GC functionality still remain to be elucidated in detail. The primary objective of the study was to determine the effect of essential fatty acids especially of ALA and CLA by abomasal supplementation in lactating cows to assess the effects on in vitro preimplantation embryo development. We analyzed the FA compositions of FF in the different dietary groups and elucidated the effects of increased concentrations of ALA and cis-9, trans11CLA on the morphology, hormone production, viability, and gene expression of cultured bovine GC
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