Effects of Dietary Crude Protein Levels on Growth Performance and Carcass Characteristics in The Black Silkie Chickens

• Main Author: 鄭兆強
• Other Authors: 鄭長義
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/69149808085660348486

碩士 === 國立屏東科技大學 === 畜產系 === 91 === Abstract The objectives of this study were to investigate the effect of dietary protein levels on growth performance and carcass characteristics in black silkies. The chickens were the black silkies. A completely randomized design（CRD）used in this experiment. 240 black silkies were randomly divided to four treatment groups with three repeats. There were 12 pens chickens, including half of the male and female. Water and feed were supplied ad libitum. Corn-soybean meal was used as a basal diet. This experiment were divided to three stage（0 to 6, 7 to 12 and 13 to 20 weeks）, according to their different growth period. The dietary crude protein（CP, %）levels were 23.0, 21.5, 20.0 and 18.5% respectively, the metabolizable energy（ME, kcal / kg） content were 3100 and the calcium（Ca）and available phosphate（AP.）were 1.1 and 0.5% of the 0 to 6 weeks. In 7 to 12 weeks, the dietary protein levels were 21.5, 20.0, 18.5 and 17.0% respectively, ME were 3000（kcal / kg）and Ca and AP. were 0.9 and 0.45%. In 13 to 20 weeks, the dietary protein levels were 20.0, 18.5, 17.0 and 15.5% respectively, ME were 3050（kcal / kg）and Ca and AP. were 0.85 and 0.4%. Different protein levels of different growth stage were to investigate the protein demand of black silkies. Each treatment took randomly 12 chickens（half of the male and female）that slaughtered and analyzed their carcass characteristics, general composition, collagen content, shear value, selenium content and phosphoserine content of meat in 16, 18 and 20th week. The results of this experiment showed that different dietary protein levels had no effect on live-weight gain, feed intake（FI）and feed conversion ratio（FCR；p＞0.05）. But increased the dietary protein levels could significantly decreased the protein efficiency ratio（PER）（p＜0.05）, the 18.5% dietary protein content of treatment group had the best result. The results of 7 to 12 weeks were like 0 to 6 weeks. The different dietary protein levels（21.5, 20.0, 18.5 and 17.0%）had no significantly effect on live-weight gain and FCR（p＞0.05）. FI and protein intake（PI）decreased significantly （p＜0.05）while dietary protein levels decreased. PER decreased significantly（p＜0.05） while dietary protein levels increased. The dietary protein level 17.0% had the best PER. In 13 to 20 weeks, different dietary protein levels（20.0, 18.5, 17.0 and 15.5%）on live-weight gain, FI and PER of black silkies had no significantly different（p＞0.05）. PI increased significantly（p＜0.05） while dietary protein level increased. FCR of dietary protein level 15.5% of treatment group had significantly higher（p＜0.05） than three other treatment groups（20.0, 18.5 and 17.0%）. The results of carcass characteristics test showed that dietary protein levels had no effect on dressing percentage of 16th week, there were not significantly different （p＞0.05）among treatment groups. There were significantly different（p＜0.05） on breast percentage but they were no concern of dietary protein levels. In sexes, the breast percentage of female had significantly higher（p＜0.05） than male. Other items, like dressing percentage, thigh percentage and abdominal fat percentage had no significantly different（p＞0.05） between sexes. The dietary protein levels had no effect the results of dressing percentage, breast percentage, thigh perentage and abdominal fat percentage of 18th week. In sexes, dressing percentage of male had significantly higher（p＜0.05） than male in dietary protein levels 18.5 and 15.0%. There were not significantly different （p＞0.05）between other treatment groups about sexes. In dietary protein level 20.0% of treatment group the breast percentage of female had significantly higher（p＜0.05） than male, but there were not significantly different（p＞0.05） between other treatment groups. The male of thigh percentage of treatment group 18.5% had significantly higher（p＜0.05）than female, but there were not significantly different （p＞0.05）between other treatment groups. Abdominal fat percentage was not concern of sexes. In 20th weeks, there were not significantly different（p＞0.05） among dressing percentage, breast percentage and thigh percentage and they were not concern of dietary protein levels. About abdominal fat percentage, the lower dietary protein level group had more abdominal fat percentage（p＜0.05）. In sexes, dressing percentage of male had significantly higher（p＜0.05） than female, but breast percentage, thigh percentage and abdominal fat percentage had no significantly different（p＞0.05）. The results of general composition analysis showed that the moisture, ash and crude fat content of breast and thigh meat in 16th, 18th or 20th week had no effected by dietary protein levels（p＞0.05）. But dietary protein levels had significantly effect on crude protein content of breast and thigh meat. The hugher dietary protein level group had more crude protein content of meat（p＜0.05）. About sexes, crude protein, crude fat, moisture and ash content of meat had no significantly different（p＞0.05） in any weeks and parts. The results of shear value showed that the shear value of breast and thigh meat in 16, 18 or 20th week had no effected （p＞0.05）by dietary protein levels. There were not significantly effected by dietary protein levels about sexes. About ages, muscle of 18th weeks in black silkies had the best shear value. Results in collagen content analysis indicated that total collagen（TC） content and thermal residual collagen（TRC）content of breast and thigh meat in 16, 18 or 20th week had effected by dietary protein levels. The higher protein level group had higher TC and TRC content（p＜0.05）. In sexes, there were not significantly effect （p＞0.05）on breast or thigh meat. The meat of black silkies selenium content was 1.35±0.13 ppm and phosphoserine content by mixed breast and thigh meat was 27.63±5.23 mg / 100g. It was good for human on health and strength. Summarized this study, the best dietary protein levels of black silkies in 0 to 6 weeks was 18.5％, 7 to 12 and 13 to 20 weeks were 17.0％. In carcass characteristics, the 18th week of black silkies were more suitable for slaughtered.