| Summary: | 碩士 === 國立中興大學 === 畜產學系 === 91 === The aim of this trial was to study the effects of castration on the appearance, carcass characteristics, muscle growth, blood constituents and lipid metabolism in Taiwan country chicken cockerels. Taiwan country chicken cockerels were castrated at 8 weeks of age. Sixteen-week-old Taiwan country chickens, including 10 capons, 5 slips and 20 normal chickens of equal sexes were selected for a 10 week ad libitum feeding trial. Results showed that the testosterone concentration in the capons and females were lower than the males. Therefore, the comb length, height and weight the significantly lower (P < 0.05). The slip weight fell between the capon and males. Slip weight was higher than capon weight (P < 0.05). The body weight, carcass weight, shank length and shank perimeter in the capon was significantly higher than the others (P < 0.05). The slip fell between the capon male. The female was significantly lower than the others (P < 0.05). The capon breast and the thigh weight was significantly heavier than the others (P < 0.05). The hepatic lipogenic enzyme activity analyses results showed that NDAP-malic dehydrogenase (MDH) activity in the capon and female chickens was significantly higher than in male chicken (P<0.05). The MDH activity in the slip was in between the capon and male chickens (P>0.05) The abdominal weight and relative abdominal fat weight of the capon and the females were significantly heavier than the male (P < 0.05). The slip fell between the capon and male. The lipid contents of the blood showed that the triacylglyceride, cholesterol, total protein, albumin and phosphate content, γ- globulin percentage and alkaline phosphatase activity of the capon was significantly higher than that of the male (P < 0.05). However, the percentage of low-density lipoprotein (LDL) was significantly lower than in male chickens (P < 0.05). The phospholipid level of the very low-density lipoprotein (VLDL) in the male chickens was higher than that in the capon (P < 0.05). Apo B was the major VLDL and LDL apolipoprotein. apo 66 kDa was next. Apo A-I was the major constituent in the high density lipoprotein, followed by apo 90 kDa and low proportion of apo in 15-20 and 37-50 kDa. Females presented a different apo, called apo VLDL-II. It appears that the increase in lipid accumulation in castrated male chickens might mainly be attributed to the increase in MDH activity and the changes in lipid transportation in the capon.
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