Comparative expression profiles of genes related to oocyte development in goats after long-term feeding with biodiesel castor industry residues

• We evaluate the inclusion of detoxified castor cake in goat feed for long periods of time.
• We examine changes in the mRNA levels in oocytes, mural granulosa and cumulus cells.
• The changes of gene expression were associated with decrease in the rate of oocyte maturation.

The aim of this study was to determine whether the consumption of detoxified castor meal (DCM) by goats over a long period of time affects mRNA levels in oocytes, and in mural granulosa and cumulus cells. A total of 41 adult does were supplemented (DCM group, n = 21) or not (control group, n = 20) with detoxified castor meal (DCM) for a period of 500 days. Then, 13 and 12 does were randomly selected for slaughter from the DCM and control treatments groups, respectively, for the determination of the number of visible ovarian follicles, retrieved cumulus-oocyte complexes (COCs), and viable and non-viable oocytes. The relative expression levels for distinct genes were determined by quantitative PCR in viable immature oocytes prior to in vitro maturation (IVM), in oocytes attaining or not the metaphase stage after IVM, as well as in granulosa cells obtained upon oocyte collection, and in cumulus cells obtained after IVM. The number of follicles ≥4 mm did not differ between treatments (overall mean 23.3 ± 2.0) and no significant differences were observed in the recovery of viable, non-viable, or total mean numbers of oocytes (control group: 44.7 ± 4.6, DCM group: 54.9 ± 5.9, respectively) between control and DCM fed goats. The maturation rate was significantly higher for control than DCM oocytes (58.0% vs. 45.3%; P < 0.05). The mRNA levels in immature COC for controls were significantly higher for GLUT1 and lower for HSP70 (P < 0.05) than for DCM. Following maturation, MII oocytes from both treatments had mRNA levels that were significantly higher for GDF9 and lower for BMP15 than for NC oocytes (P < 0.05). In cumulus cells, the mRNA levels were significantly higher for LHR, FSHR, LeptinR, and IGF1, and lower for MnSOD in the control group compared with the DCM group (P < 0.05). In conclusion, the inclusion of DCM in goat feed for long periods of time changed gene expression in immature oocytes and in cumulus cells. This was reflected by a decrease in the in vitro oocyte maturation rate.