Propylene glycol supplementation modulates the luteal transcriptome in dairy cows

Our objective was to evaluate the effects of oral propylene glycol supplementation (PG; 300 mL) on the corpus luteum (CL) transcriptome of non-pregnant, non-lactating dairy cows. Sixteen cows were synchronized for estrus and assigned to four treatments in a Latin square design: CC, water pre- and post-follicular deviation (FD); CP, water pre- and PG post-FD; PC, PG pre- and water post-FD; and PP, PG pre- and post-FD. CL samples were collected by transvaginal biopsy on D15 of the estrous cycle and D10 after subsequent ovulation, followed by RNA sequencing. The contrast D10 vs. D15 within treatment identified 1994 differentially expressed genes (DEG), with the strongest response observed in PC, followed by CC and CP. In the treatment vs. control contrast, 66 DEG were detected on D15, with the greatest response in PP, followed by CP and PC. On D10, 1206 DEG were identified, with the strongest modulation in PC, whereas CP and PP showed limited responses. PG altered the expression of genes involved in steroidogenesis, lipid metabolism, and vascular and structural support of the CL. No differences among treatments were observed in dominant follicle diameter or progesterone concentrations (P > 0.05). PG increased insulinemia within 30 min of administration, and insulin was strongly and positively correlated with CL volume (r = 0.86; r² = 0.75; P = 0.02). These findings indicate that glucogenic nutritional supplementation can modulate ovarian molecular pathways and potentially affect luteal function in dairy cows, even under positive metabolic balance conditions.