90 LIPID CONTENT OF IN VIVO- AND IN VITRO-PRODUCED JERSEY AND HOLSTEIN CATTLE EMBRYOS AND THE EFFECT OF FORSKOLIN ON EMBRYO LIPID REDUCTION

Abstract

Jersey embryos have been suggested to have higher lipid content and lower tolerance to cryopreservation. In addition, in vitro-produced (IVP) bovine embryos have darker cytoplasm as a consequence of higher lipid accumulation than in vivo-derived embryos, associated with impaired embryo quality and reduced cryotolerance. Forskolin is an adenylate cyclase activator that regulates cAMP levels in cells and has been shown to induce lipolysis in IVP embryos. We hypothesised that the lipid content of in vivo-produced and IVP Jersey embryos is higher than respective Holstein embryos and that forskolin would reduce lipid content of IVP embryos. The objectives of this experiment were (1) to analyse lipid content of in vivo and IVP Jersey and Holstein cattle embryos and (2) to evaluate the effect of forskolin added to IVP culture media. The factorial experimental design used two breeds (Holstein and Jersey) and three embryo production methods (in vivo, IVP, and IVP + forskolin). IVP embryos (n = 27 blastocysts) were collected from super-stimulated donors by routine procedures 7.5 days after AI. IVP embryos (n = 259 blastocysts) were produced by standard procedures; briefly, oocytes were aspirated from 2- to 8-mm follicles from slaughterhouse ovaries and matured for 24 h in SMM medium (BoviPro, MOFA Global, Verona, WI, USA). Matured oocytes were fertilized using semen from two different bulls for each breed, and embryos were cultured in BBH7 medium (BoviPro, MOFA Global) alone or with the addition of forskolin (10 µM) at Day 5 of culture at 38.5°C in 5% O₂, 5% CO₂, and 90% N₂. The lipid content of embryos was quantified by staining Day 7 blastocysts with 1 μg mL^–1 Nile red dye (580–596 nm), after which a digital photograph of the equatorial part of the embryo was taken at 40×, and fluorescence intensity (FI) was measured with Image Pro software. Data (Table 1) were analysed by ANOVA, and means were compared using Tukey’s HSD. Jersey and Holstein IVP embryos had higher lipid content than Holstein in vivo-produced embryos (P < 0.05), but were not different than Jersey in vivo-derived embryos (P > 0.1). Forskolin lowered the lipid content (P < 0.05) of both IVP Jersey and Holstein embryos and was not different (P > 0.1) than in vivo-produced embryos. Addition of forskolin to embryo culture media has the potential to lower embryo lipid accumulation and possibly improve embryo viability and cryotolerance of IVP embryos. Further studies including cryopreservation and transfer of IVP + forskolin embryos to recipients are necessary to corroborate the findings of the present study.

Table 1.  Fluorescence intensity of in vivo-produced and IVP Jersey and Holstein embryos