In vitro addition of DHA and IGF-I increases the progressive motility of cryopreserved stallion semen

Abstract

High seminal quality is important to achieve acceptable pregnancy rate following artificialinsemination with cryopreserved semen in the equine industry. Docosahexaenoic acid (DHA) is anomega-3-polyunsaturated acid, which improves the integrity of the spermatozoa membrane duringtemperature changes. Insulin-like growth factor-I (IGF-I) is a protein hormone that helps mainlyglucose to enter spermatozoa and it is an antioxidant. The aim of this study was to assess the effectof the in vitro addition of DHA in combination with IGF-I to frozen-thawed stallion semen. Threeejaculates from each of three Irish Sport Horse stallions were collected, the gel fraction was removedand semen was diluted in a 1:1 ratio using extender, centrifuged (1.000 g) for 10 minutes at 32 °Cand ressuspended to 100 x 106 spermatozoa/mL in freezing extender. Semen was cooled to 4 °C,packed into 0.5 mL straws, frozen and stored under liquid nitrogen at -196 °C. Straws were thawedat 37 °C for 30 seconds, semen was diluted to 25 x 106 spermatozoa/mL and split in four treatmentsadding 0 or 1 ng of DHA /mL and 0 or 100 ng of IGF-I /mL: DHA0, DHA0 + IGF-I, DHA1 and DHA1+ IGF-I. Semen was incubated at 32 °C and after 30 minutes, total motility (TM), rapid progressivemotility (PM), viability and acrosome integrity were assessed. After 60 and 120 minutes, TM and PMwere assessed again. Post-thawed PM was higher (P < 0.05) when DHA1 + IGF-I was added, butthere was no effect of the addition of DHA and IGF-I to TM, viability or acrosome integrity (P > 0.05).Keywords: Equine. Spermatozoa. Omega-3. Antioxidant. Hormone.