# Could Individual Variability in Resistance to Cryopreservation (“Freezability”) Serve as a Biomarker Reflecting Boar Fertility?

## TL;DR

This study explores if how well pig semen resists freezing can help identify infertile boars earlier, potentially improving breeding efficiency.

## Contribution

The study introduces the novel idea that semen freezability could act as a complementary biomarker for boar fertility when combined with fresh semen motility.

## Key findings

- High-fertility boars had better fresh semen motility but not necessarily better post-thaw quality.
- Boars with high fertility and poor freezability had the worst post-thaw semen quality.
- Freezability alone does not predict fertility, but combining it with motility improves early detection of low-performing boars.

## Abstract

Detecting male pigs with low fertility early is a major challenge for pig farmers, as these animals often go unnoticed until they cause serious economic losses. In this study, we explored whether freezing semen could help reveal hidden fertility problems. We evaluated semen from several boars, analyzing its quality before and after freezing, and compared this with the fertility records of each animal. We found that boars with higher fertility generally had better semen quality before freezing, especially in terms of sperm movement. However, these differences mostly disappeared after freezing. On the other hand, boars whose semen handled freezing well did not always have higher fertility. Interestingly, semen from boars with both high fertility and poor resistance to freezing showed the lowest quality after thawing. This suggests that freezing might help uncover sperm problems that normal tests miss. While freezing ability alone does not predict fertility, combining it with sperm movement in fresh semen could help identify low-performing boars early. This would save time and money for the pig industry and improve overall breeding success.

Subfertile boars often go undetected until they cause significant reproductive losses. Current semen quality assessments are limited in their ability to predict fertility, highlighting the need for complementary biomarkers. This study explored whether semen freezability could serve as an indirect indicator of boar fertility. Eighteen boars were classified based on historical fertility records and semen freezability, assessed by post-thaw quality. Fresh and post-thaw semen samples were analyzed using the CASA system and fluorescence microscopy. High-fertility boars showed significantly better motility and functional sperm parameters in fresh semen compared to low-fertility boars. However, these differences were mostly lost after cryopreservation. Conversely, boars with good freezability had consistently better post-thaw semen quality, though this did not correlate directly with higher fertility outcomes. Notably, a combined analysis revealed that boars with both high fertility and poor freezability had the lowest post-thaw semen quality. This suggests that cryopreservation may expose hidden sperm defects not detectable in fresh semen. Total motility was the only parameter associated with both fertility and freezability. In conclusion, while freezability alone may not directly predict fertility, it may help identify low-performing males. The combined assessment of fresh semen motility and freezability could support more effective boar selection strategies.