145 THE INFLUENCE OF PROPYLENE GLYCOL DRENCHING ON THE SUPEROVULATORY RESPONSE AND EMBRYO QUALITY IN HIGH-YIELDING DAIRY COWS

Abstract

Genetic improvement of dairy cows increased markedly over the last decades; this has marked increased milk yield, which has been associated with reduced fertility parameters. The objective of this study was to determine the effects of feeding propylene glycol (PG) on superovulatory responses of 50 dairy cows and on their embryo quality and quantity. Starting at 1 week before the application of superovulatory regimen, each cow received once daily an oral dose of 150 g of PG (PG group) or water (control group). All cows were superovulated with a total dose of 400 mg of FSH administrated twice daily in decreasing doses over 4 consecutive days. Embryos were recovered nonsurgically 7.5 days after the onset of oestrus using a 2-way catheter. Evaluation of embryo quality was done according to the IETS manual based on 1 to 4 grades. Grade 1 embryos were transferred after freezing; grade 2 and 3 embryos were freshly transferred. The results showed that the number of total ova/embryos recovered, grade 1 embryos, and the number of transferable embryos were significantly higher (P = 0.048, 0.015, and 0.014, respectively) in the PG group (10.33 ± 1.9, 7.08 ± 1.7, and 7.92 ± 1.6, respectively) when compared with control group (6.09 ± 0.9, 2.11 ± 0.45, and 3.92 ± 1.25, respectively). Insignificant increase in grade 2 and grade 3 embryos was indicated in the control group (1.37 ± 0.3 and 0.51 ± 0.18, respectively) when compared with PG group (0.75 ± 0.28 and 0.25 ± 0.13, respectively). On the other hand, the results indicated that there was an increase in the number of degenerated embryos and unfertilized ovum in the PG group (2.33 ± 0.85) compared with control group (2.09 ± 0.6). In conclusion, these results suggested that administration of PG has the ability to positively improve the superovulatory response and embryo quality in high-yielding dairy cows.