Hypo-osmotic swelling test discriminates potentially more viable boar spermatozoa diluted using various extenders at different storage times

Abstract

Boar semen samples are normally tested across multiple parameters to ensure maximum performance. However, conventional semen quality parameters may not provide a robust indication of the fertility potential of spermatozoa. This study examined sperm plasma membrane integrity using the hypo-osmotic swelling test (HOST). It was hypothesized that HOST could effectively select possibly more viable spermatozoa despite normality in other parameters. Semen samples (n=15) from five boars were processed into AI doses (~37.5 x 106 spz/mL) using five different commercial extenders: Androstar Plus, BTS, Dilufert Silver, MIII, and VIM. Using Sperm Class Analyzer® CASA system, total and progressive motility, and plasma membrane integrity using dye exclusion test and HOST were evaluated at Day 0, Day 3, and Day 5 of storage. Boar 2 tended to have more HOSTpositive spermatozoa over the other boars in Dilufert Silver, VIM, and Androstar Plus extenders in both Day 3 and Day 5 and in BTS at Day 3. Several significant interactions were also observed when storage times, extenders used, and the kind of boars were considered. Moreover, the total and progressively motile spermatozoa did not vary between boars and different extenders across different storage durations, except for MIII between Day 0 and Day 5. Hypo-osmotic swelling test (HOST) could serve as a useful test for detecting the functional integrity of boar sperm and sensitive enough to discriminate potentially more viable spermatozoa particularly when applied in small-scale swine operations without advanced capacity for comprehensive semen analyses.