早期限饲对肉鸡肌肉生长及肌纤维类型的影响

采用隔日限饲的方式对1～14日龄三黄肉鸡仔鸡进行早期限饲处理,后恢复自由采食直至63日龄试验结束,以分析早期限饲对肉鸡肌肉生长和肌纤维类型的影响。分别于14和63日龄随机选取对照组和早期限饲组肉仔鸡各20羽,屠宰后采样,记录腓肠肌外侧头重量并采用相对定量RT-PCR的方法检测其不同类型肌纤维肌球蛋白重链mRNA基因表达。结果表明,早期限饲组体重及腓肠肌外侧头重均低于对照组(P<0.05,n=20)。14日龄早期限饲组慢肌及快红肌肌球蛋白重链mRNA表达水平显著高于对照组(分别为P<0.01和P<0.05,n=10),快白肌肌球蛋白重链基因表达显著低于对照组(P<0.05,n=10)。63日龄早期限饲组慢肌肌球蛋白重链mRNA基因表达显著低于对照组(P<0.05,n=10),快红肌和快白肌肌球蛋白重链与对照组相比均无差异(P>0.05,n=10)。结果提示:(1)早期限饲阻碍了肌纤维类型的转化,延缓了肌肉的发育及增重,最终引起整体体重的下降;(2)早期限饲对肌肉肌纤维成分具有持久影响,其影响一直持续到63日龄上市。

Effect of Early Feed Restriction on Muscle Growth and Myofiber Types in Broiler Chickens

For exploring the effect of early feed restriction on muscle growth and myofiber types in broiler chickens, newly hatched broiler chickens were allocated randomly into control and early feed restriction(ER) groups. Chickens in control group were fed ad libitum for the whole period of investigation, while the ER group were subjected to intermittent feed restriction with feed provided on alternate days from hatch to 14 days of age (14 d), followed by ad libitum feeding till the end of the experiment on 63 d. Twenty chickens from each group were sacrificed on 14 and 63 d respectively, lateral gastrocnemius muscle was taken for myofiber typing by relative quantification of mRNA expression for three different types of myosin heavy chain(MyHC): slow myofiber MyHC (SM MyHC), red fast-twitch myofiber MyHC (FRM MyHC) and white fast-twitch myofiber MyHC (FWM MyHC) by RT-PCR using 18S rRNA as an internal-standard. The body weight and the lateral gastrocnemius muscle weight were significantly lower in ER group on 14 d and 63 d (P <0.05, n =20). ER group exhibited significantly higher SM (P <0.01, n =10) and FRM (P <0.05, n =10) MyHC mRNA expression but lower FWM (P <0.05, n =10) MyHC mRNA compared with their control counterparts on 14 d. On 63 d however, a significant down-regulation was observed in ER group for SM MyHC expression(P<0.05, n =10), whereas no significant differences were detected for both FRM and FWM MyHC mRNA expression between two groups(P >0.0, n =105). These results indicate that, 1) early feed restriction may delay the conversion from slow-twitch myofiber to fast-twitch myofiber, resulting in retarded muscle growth that may account for the decreased body weight, 2) the influence of early feed restriction on myofiber types is long-lasting, significant difference still seen after 7 weeks when chickens reach the marketing age.