The impact of birth weight on spermatogenesis in boars

Low birth weight piglets are a reality in commercial farms and have been associated with functional disorders of several organs systems, resulting in deleterious consequences during postnatal life. There is strong evidence that low birth weight pigs present compromised postnatal growth and performance and poor meat quality. However, reports of birth weight effects on the reproductive system are scarce, especially in boars. Therefore, the aim of the present study was to evaluate testicular parameters associated with spermstogenesis in different birth weight boars.

Forty-eight newborn male pigs Agroceres-PIC genotype (crossbred Landrace, Large White and Duroc) from 24 litters were selected immediately after birth, and identified as falling into two birth weight categories: high (HW: range 1.85 to 2.15 kg; n=24) and low (LW: 0.85 to 1.15 kg; n=24) littermates. A sub-set of 12 pairs of male littermates from each experimental group was orchiectomized at eight days post-partum and another sub-set of 12 pairs of male littermates, orchiectomized at eight months of age. Testicular samples were collected and subjected to different preparations according to the histomorphometrical and sperm head count analysis. Data were analyzed as a randomized complete block design and the comparison between means was performed by t-test.

HW boars had greater body and testicular weights than LW boars at both ages (P < 0.05). Overall, birth weight affected somatic and germ cells numbers in the neonatal testis and spermatids numbers in the post-pubertal testis, as shown by higher number of those cells in HW boars (P < 0.05). LW was not associated with depletion in spermatogenesis efficiency, represented by mitotic, meiotic and Sertoli cell efficiency indexes. Further evidence of normal spermatogenesis efficiency was established by counting type A spermatogonia and preleptotene spermatocyte per seminiferous tubule cross section, which were similar between both experimental groups. However, a significant reduction in the number of pachytene spermatocyte and round spermatid was observed in LW boars (P < 0.05), that caused a decrease in the total number of round spermatids (P < 0.05). These differences were proportional to testis size and may not be associated with impaired testicular function.

These findings suggest that prenatal programming of testis development will predetermine the reported relationship between adult testis size and lifetime semen production. Therefore, additional studies are necessary to better understand the effects of birth weight on other reproductive parameters related to semen quality and fertility.

Disclosure of Interest: None Declared.