Testicular histomorphometrics including Sertoli cell quantitation for evaluating hatchability and fertility issues in commercial breeder-broiler roosters

Testicular histomorphometric methods were developed for the investigation of fertility and hatchability problems in commercial broiler-breeder roosters. Sertoli cell (SC) evaluations were emphasized in view of their role in influencing embryonic testicular organogenesis and spermatogenesis in adults. H&E stained sections prepared from formalized tissues were examined. SC evaluations were mostly made from computer generated images using image analysis software, but were also compared to direct counting with ocular grid reticle. Other measurements were germinal epithelial and total seminiferous tubule widths, quantification of individual spermatozoa and sperm clusters, and determinations of stromal area. Age-associated changes in SC occurred between 15 to 54 wk of age. A significant reduction in SC concentration occurred at 29 wk of age (P < 0.001) that corresponded with the histologic initiation of spermatogenesis. Expanded morphometric evaluations were performed on 59-week-old roosters comparing a flock having good body condition and footpad scores with normal testicular and body weights (optimal profile or OP group) to a second flock demonstrating relatively poor expression of these parameters and decreased fertility (sub-optimal profile or SOP group). Significant reductions (P < 0.05) in SC concentration, spermatozoa, and tubular widths, but an increased percentage of stroma area occurred in SOP compared to OP flocks. SC results also correlated well with testes weight. A unique finding was a significant relationship between decreasing SC concentration and increasing severity scores for footpad lesions. Differences in all histomorphometric parameters occurred between flocks demonstrating good hatchability compared to flocks exhibiting either low or decreasing hatchability. Significant reductions in SC and other morphometric parameters were observed for the poor relative to good hatchability group. A strong positive association was observed for SC results using computer generated images and direct reticle ocular counting (R = 0.80). Replicate counts on control sections demonstrated generally good reproducibility of methods between experiments. The findings are supportive of the value of testicular histomorphometrics for evaluations of hatchability issues in commercial roosters.