Gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens.

This study investigated gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens. Thirty male chickens were caponized at 8 weeks (capons); 15 capons were injected with estrogen (5 mg/bird estradiol 3-benzoate) every 2 weeks from 8 to 28 weeks, and 15 sham-operated male (shams) chickens and 15 females were selected for this trial. The results showed that the shams had lower relative abdominal and chest subcutaneous fat than females (P < 0.05). The estrogen-treated capons had greater relative abdominal and chest subcutaneous fat than shams and capons (P < 0.05), which might result from higher blood very low-density lipoproteins and triacylglycerol concentrations (P < 0.05). Caponization could dramatically increase relative abdominal fat (506%; P < 0.05). The shams had higher tibia weight and biomechanical properties, such as maximum bone strength and bending moment values than the capons (P < 0.05). Tibia biomechanical properties were reduced by estrogen treatment (P < 0.05). The females obtained the lowest biomechanical value in all treatments (P < 0.05). Histological examination revealed cavity formation in the cortical bone of estrogen-treated capons and female chickens, which suggested that estrogen reduced bone biomechanical properties by destroying its structural integrity.