Effects of Caponization and Testosterone on Bone and Blood Parameters of SCWL Male Chickens

This study was to investigate the caponization effects on bone characteristics in male chickens, and the optimum testosterone implantation dosage on bone characteristics improvement. Healthy Single Comb White Leghorn cockerels were caponized at 12-wk-old and selected at 16-wk-old for a 10-wk feeding experiment. Fifteen intact male and caponized male chickens (capon) respectively were assigned to trial 1. Ten sham-operated chickens and 40 capons (randomly allocated into four treatments) were implanted with cholesterol (1.62 mm i.d., 3.16 mm o.d., $9.24{\pm}0.36$ mg), low (1 mm i.d., 3 mm o.d., $5.88{\pm}0.23$ mg), medium (1.62 mm i.d., 3.16 mm o.d., $9.81{\pm}0.17$ mg) or high dose (2 mm i.d., 4 mm o.d., $16.7{\pm}0.24$ mg) of testosterone in trial 2. The results from trial 1 showed that the tibia length, relative tibia weight, breaking strength, bending moment and stress in intact males were higher than capons (p<0.05). The blood phosphorus concentration in capons was higher than the intact male chickens (p<0.05). Caponization also resulted in more antrums and osteoclasts within periosteum and cortical bone from histological observation. In trial 2, the adverse impact of caponization on the bone breaking strength, bending moment and stress could be alleviated through medium dose testosterone implantation. It appears that caponization reduced androgen secretion hence influenced the biomechanical characteristics of bone (tibia) and these adverse effects could be alleviated through appropriate dose of testosterone implantation.