PSX-5 Influence of sperm viability on the morphological status of boar sperm.

Abstract The importance of evaluating boar sperm morphology, relative to providing a functional population of cells for fertilization, is understood. Generally, an inverse relationship exists between percent abnormal sperm and a boar’s fecundity potential. The authors are not aware of any information in the literature on the percentage morphological differences when assessing whole samples (both live and dead boar sperm) versus just live boar sperm at the time of fixation. Given that a boar semen sample rarely harbors 100% live and intact sperm, it may be of interest to know or understand the morphological status of live versus dead sperm at the time of fixation. Logic would suggest that more abnormal sperm would be identified as dead cells versus live sperm. The objective of the present study was to evaluate the percent normal morphology of boar sperm based on viability using the stained smear method in conjunction with a membrane integrity stain (modified eosin-nigrosin). Semen samples (n=40) from a Midwest USA boar stud were collected during the spring months of 2024. Most samples (>85%) were sourced from boars passing CASA analysis standard laboratory thresholds for morphology. Stained smears were prepared to allow differential morphology scoring between all cells (ALL) and intact-only cells (LIVE). Differential interference contrast microscopy was used for evaluation (1250x under oil immersion) and the data recorded into an Excel file. A total of 100 sperm were evaluated-within sample – for both ALL and LIVE for each of the 40 samples. The Paired T-test was used for testing whether the means of the two groups were different. The mean percent (±SD) normal sperm morphology for ALL and LIVE was 80.1 (+4.2) and 82.7 (+5.3), respectively, which was significant (P=0.001). Significant differences were also found to exist in other morphology categories. The information may be useful for understanding semen quality dynamics and decision-making relative to the downstream processing of boar ejaculates for use in AI.