Abstract
Background:
Sperm morphology assessment is related to the ejaculate quality, which varies in males and breeds. Routine microscopy does not accurately assess deeper morphological or cryodamage Comparative quality assessment of indigenous and exotic breed spermatozoa yet to characterize under high resolution microscopy.

Aim:
This study aimed to identify dimensional, deeper morphological and cryodamage differences in the fresh and frozen sperm of Indian and exotic pig breeds.

Methods:
Fresh and frozen-thawed boar spermatozoa of indigenous (Ghungroo) and exotic (Large White Yorkshire) breeds were used to estimate the deep morphological abnormalities, morphometry, and cryodamage using scanning electron microscopy (SEM). Analysis of variance followed by Tukey’s post hoc test was used for data analysis.

Results:
Under phase contrast microscopy, the quality parameters of fresh semen were found to be within acceptable limits, showing no significant differences (p > 0.05) except for volume and concentration between the two breeds. Furthermore, the quality after thawing was subpar in both breeds. In the examination under SEM, the morphometric dimensions of spermatozoa from the indigenous breed were found to be non-significantly (p > 0.05) lower, with the exception of midpiece width and the perimeter of cytoplasmic droplets, compared to those from the exotic breed. Among the deep morphological abnormalities observed in fresh semen, a significant difference (p<0.05) was noted between the indigenous and exotic breeds for damaged acrosomal crescent, extruded acrosomal vesicle, cracks on the acrosome, bent tails, fragmented tails, plasma membrane damages (on the head and tail), and multiple vesicles (on the head, midpiece, and tail). Extensive cryodamage was noted after thawing, with significant differences (p<0.05) in misshapen heads, multiple vesicles on the head, and damage to the acrosomal membrane, crescent, and tail membrane between the indigenous and exotic breeds.

Conclusion:
SEM is better for assessing deeper sperm morphological abnormalities or cryodamage. Indigenous breed spermatozoa were similar to their exotic counterparts in terms of morphometric dimensions, structural integrity, and cryoresilience. This study opened newer opportunities in semen testing for the early detection of fertility or subfertility for the evaluation of boar breeding soundness.

Key words: Boar; Cryodamage; Electron microscopy; Sperm.