Association of allelic variants of thyroid-binding globulin with puberty in boars and responses to hemicastration

Hemicastration of males increases weight of remaining testis when conducted before Sertoli cells cease to proliferate. The current studies re-examined responses to hemicastration in one-quarter Meishan crossbred boars that differed for two alleles of thyroid-binding globulin (TBG). In the first experiment, boars at 25 days of age with either allele did not differ in degree of testicular development; however, at 56 days, boars with the C allele had more advanced testicular development than littermates with the A allele as evidenced by testes with seminiferous tubules of larger diameter (P < 0.008) and greater weight (P < 0.05). At 10 months of age, boars hemicastrated at 25 days had a similar number of Sertoli cells in their single testis compared with both testes of control boars. However, in boars hemicastrated at 56 days number of Sertoli cells was less than the total number of Sertoli cells in the bilaterally intact controls; this reduction was greater (P < 0.05) in boars with the C allele than in those with the A allele. The second experiment confirmed earlier (P < 0.05) pubertal development in boars with the C allele relative to littermates with the A allele based on larger tubular diameter and the greater proportion of tubules with a distinct lumen at 60 and 80 days of age. These studies establish that boars with the C allele for TBG attain puberty at a younger age than those with the A allele thereby linking rate of pubertal development of boars with TBG or with gene(s) on the X chromosome in close proximity of TBG.