早期和后期限饲对肉鸡采食量及下丘脑POMC、NPY和瘦素受体mRNA转录的影响

Effect of early and late feed restriction on feed intake and hypothalamic NPY,POMC and leptin receptor gene transcription in broilers

采用隔日限饲方式对0～2周龄(早期)和7～9周龄(后期)三黄肉鸡进行限饲处理,分别于2和9周龄时各组随机选取10羽肉鸡宰杀后采样。结果显示:与对照组相比,早期限饲组鸡体重极显著降低(P<0.01,n=40),后期限饲组鸡8周龄时体重显著降低(P<0.05,n=20),9周龄时无显著差异(P>0.05,n=10);早期限饲组鸡的平均日采食量低于对照组,而后期限饲组鸡平均日采食量升高;限饲期间肉鸡料重比增加,而自由采食期间无差异。Real-time PCR测定结果显示:肉鸡下丘脑神经肽Y(NPY)、阿片-促黑素细胞皮质素原(POMC)和瘦素(leptin)受体mRNA转录丰度均随日龄增加而显著升高(P<0.05,n=10);早期限饲仅引起下丘脑POMC基因转录的显著下调(P<0.05,n=10),后期限饲对下丘脑NPY、POMC和leptin受体mRNA无显著影响(P>0.05,n=10)。以上结果提示:早期2周的隔日限饲显著减少了肉鸡的采食量,从而最终导致体重的显著下降。下丘脑POMC、NPY和leptin受体基因在转录水平上表现出对慢性限饲的适应现象且差异不显著。

Newly hatched broiler chicks were allocated randomly into control and early feed restriction（ER）groups and later feed restriction（LR）groups.The ER chickens were deprived of food on alternate days for the first 2 weeks from post hatch,and followed by ad libitum feeding for the subsequent 7 weeks,and LR chickens followed the same procedure from 7 to 9 weeks old.During the whole investigation periods,body weight,average daily feed intake and the ratio of feed to gain were caculated.10 chickens from each group were sacrificed on 2 and 9 weeks old,respectively,and the hypothalamus tissues were taken for pro-opiomelanocortin（POMC）,neuropeptide Y（NPY）and leptin receptor mRNA expression by relative RT-PCR using 18S rRNA as an internal-standard.The body weight of ER group chickens exhibited significantly lower compared with their control and LR counterparts during the whole experimental periods.Compared with control chickens,the body weight of LR chickens at the first week of food restriction decreased significantly,however,there was no difference at the end of the second week food restriction.Average daily food intake was continuously lower in ER group than that of control group from 1-to 8-week-old,on the contrary,which was much higher in LR group during the 2 weeks food restriction.The ratio of feed to gain increased in ER and LR groups during the feed restriction.RT-PCR results showed that,the mRNA expression of POMC,NPY and leptin receptor in the hypothalamus showed an age-dependent increase,and a significant down-regulation of hypothalamic POMC gene expression was observed in ER but not in LR group compared with control group,whereas no significant differences of POMC,NPY and leptin receptor mRNA expression in the hypothalamus was detected in LR chickens on 9 weeks old.In this study,the results suggested that early feed restriction retarded feed intake,which may account for the lean body weight during the whole investigation.On the other hand,the stable expression of appetite related genes in the hypothalamus may be related to the adaptation of chickens to the status of feed restriction.