Abstract

Freeze-thaw procedures induce structural and functional changes in sperm. It is important to use post thaw sperm selection procedures that can retrieve highly functional sperm. The aim of this study was to compare the efficiency of the Swim-up and Equipure (R) in the selection of functional sperm of thawed equine semen. Semen of four Chilean Criollo reproductive stallions (A, B, C and D) were frozen and thawed using a standard protocol and processed separately (n = 15) : I. Swim-up (SU) and II. Equipure (R) (EQ). Post sperm selection, was determined by flow cytometry. Viability and plasma membrane integrity (SYRB-14/PI), mitochondrial membrane potential (YDm, JC -1), acrosome membrane integrity (FITC-PSA/PI). Progressive motility (%) was higher (P<0.05) in two animals per SU compared with EQ, A (55.7 +/- 5.8% vs. 38.17 +/- 3.7%) and C (37.5 +/- 7.0% vs. 32 +/- 2.1%, respectively). The viability and integrity of the plasma membrane (%), three animals showed differences (P<0.05), being higher for SU in two animals compared with EQ (A: 54.3 +/- 1.7 vs. 36.7 +/- 1.9, C: 36.1 +/- 5.7 vs. 29.4 +/- 4.8 and D: 34.4 +/- 9.4 vs. 52.7 +/- 5.2, respectively), only one animal was higher EQ. In YDm (%), significant differences were detected (P<0.05) in all four animals, being higher in SU compared with EQ (A: 69.1 +/- 8.6% vs. 47.4 +/- 3.3% B: 59.34 +/- 12.3% vs. 24.8 +/- 1.5%, C: 54.9 +/- 12.3% vs. 43.2 +/- 3.1% and D: 53.1 +/- 17.6% vs. 37.5 +/- 5.7%, respectively). The results obtained in this study showed that sperm selection methods Swim-up and Equipure (R) can retrieve different functional sperm quality in frozen-thawed equine semen, and that individual differences were registered among animals with respect to methods. In the Swim-up method a tendency for selecting higher functional quality in thawed equine sperm was observed when compared to Equipure (R).