Effect of caponization and exogenous androgen implantation on muscle characteristics of male chickens.

This study examined the effects of caponization and different exogenous androgen implantations on the growth performance and muscle characteristics of caponized male chickens. Male Single Comb White Leghorn chickens were caponized at 12 wk of age and selected at 16 wk of age for a 10-wk feeding period. Sixteen intact males and caponized (capon) chickens each were assigned for trial 1. Sixteen sham-operated male chickens (sham) and 64 capons were selected for trial 2, in which capons were randomly divided into cholesterol (CHOL), testosterone (TES), 5alpha-dihydrotestosterone (5alpha-DHT), or 19-nortestosterone (19-NorT) implantation at 16, 20, and 24 wk of age, with feeding to 26 wk of age. The result from trial 1 showed that caponization improved BW gain and feed conversion rate (P < 0.05) and decreased the comb length, height, and weight (P < 0.05). Breast muscle weight and gastrointestinal tract weight were higher in capons compared with intact males (P < 0.05). In trial 2, CHOL implantation decreased relative thigh muscle weight compared with the sham (P < 0.05), and only 19-NorT implantation increased relative thigh muscle weight to the compatible level with the sham (P > 0.05). 19-Nortestosterone and 5alpha-DHT implantations showed lower crude fat in the pectoral major muscle than CHOL (P < 0.05) and reached a compatible level with the sham (P > 0.05). All androgen implantation groups showed higher myofibrillar ATPase activity than CHOL (P < 0.05), and 19-NorT and 5alpha-DHT had the highest level (P < 0.05). Only 19-NorT implantation demonstrated higher shear value than CHOL (P < 0.05) to the compatible level with the sham (P > 0.05). Androgen implantation increased emulsifying capacity compared with CHOL (P < 0.05) and reached a compatible level with the sham (P > 0.05). Caponization decreased the blood TES concentration in male chickens, leading to changes in growth performance and muscle characteristics. After different androgen implantations in capons, 19-NorT showed the most effective results in increasing muscle quality and quantity, followed by the 5alpha-DHT and TES.