育成期饲粮代谢能水平对开产时如皋黄鸡生长发育的影响

本试验旨在研究8～18周龄饲粮代谢能(ME)水平对8周龄至开产时(20周龄)如皋黄鸡生长性能以及屠体、内脏器官、鸡冠、骨骼、消化道和繁殖器官发育的影响。试验选用8周龄体况良好、体重接近的如皋黄鸡360只，随机分成3组，每组8个重复，每个重复15只鸡。8～18周龄，试验鸡分别饲喂ME水平为10.88、11.30和11.72 MJ·kg^-1、其它营养素水平相同的试验饲粮，18周龄～开产(20周龄)，各组试验鸡均饲喂相同营养水平的预产期试验饲粮。试验期12周。结果表明：1)随8～18周龄饲粮ME水平增加，蛋鸡18周龄体重、8～18周龄平均日增重(ADG)和平均日代谢能摄入量(MEi)均显著线性增加(P<0.05)，8～18周龄和8～20周龄料重比(F/G)和粗蛋白质转化比(CPCR)均显著线性减小(P<0.05)。2)8～18周龄饲粮ME水平对18和20周龄如皋黄鸡屠体、内脏器官和消化道发育均无显著影响(P>0.05)。3)18周龄蛋鸡胫骨重和胫骨率均随8～18周龄饲粮ME水平增加先减小后增加(P<0.05)。8～18周龄饲粮ME水平对18周龄鸡冠和股骨以及20周龄鸡冠、胫骨和股骨发育均无显著影响(P>0.05)。4)18周龄蛋鸡卵巢基质指数和小黄卵泡指数均随8～18周龄饲粮ME水平增加显著线性增加(P<0.05)，8～18周龄饲粮ME水平对18周龄其它繁殖器官以及20周龄各繁殖器官发育均无显著影响(P>0.05)。由此可知，8～18周龄饲粮ME水平为11.72 MJ·kg^-1时，能显著增加18周龄体重和8～18周龄ADG，改善8～18周龄F/G和CPCR，促进卵巢基质和小黄卵泡发育，但饲粮ME水平对开产时(20周龄)蛋鸡生长发育指标均无显著影响。本研究表明，将蛋鸡育成期和预产期结合研究具有更重要的实践意义。

Effects of Dietary Metabolizable Energy Levels during Rearing on Growth and Development of Rugao Yellow Chicken at the Initiation of the Laying Period

This experiment was conducted to evaluate the effects of dietary metabolizable energy (ME) levels during rearing on growth performance and the development of Rugao yellow chicken at the initiation of the laying period. Three hundred and sixty 8-week-old Rugao yellow chicken with similar body weight were assigned to 3 groups with 8 replicates per group and 15 hens per replicate. The pullets were fed one of three diets that were nutritionally equal with the exception of ME levels of 10.88, 11.30, and 11.72 MJ·kg^-1 from 8 to 18 weeks of age. From 18 to 20 weeks of age, all pullets were fed a diet with the same nutritional level. The trial period lasted for 12 weeks (from 8 to 20 weeks of age). The results showed as follows:1) The body weight of hens at 18 weeks of age, the average daily weight gain (ADG) and the average daily ME intake (MEi) of hens aged from 8 to 18 weeks increased linearly (P<0.05), while the ratio of feed to gain (F/G) and the ratio of CPi to gain (CPCR) of hens aged from 8 to 18 and 8 to 20 weeks decreased linearly (P<0.05) with the increase of dietary ME levels from 8 to 18 weeks of age.2) The development of carcass, internal organ and digestive tract at 18 and 20 weeks of age were not significantly affected by dietary ME level from 8 to 18 weeks of age (P>0.05). 3) The tibia weight and tibia index showed a decreasing and then increasing response to increasing dietary ME level from 8 to 18 weeks of age (P<0.05), while there was no significant difference in the development of comb and femur at 18 weeks of age and the development of comb, femur and tibia at 20 weeks of age. 4) The ovary stroma index and small yellow follicle index at 18 weeks of age increased linearly with the increase of dietary ME levels from 8 to 18 weeks of age, while there was no significant difference in the other reproductive organs at 18 weeks of age and all the reproductive organs at 20 weeks of age. It was indicated that the body weight of hens at 18 weeks of age and the ADG of hens aged from 8 to 18 weeks were increased, the F/G and CPCR of hens aged from 8 to 18 weeks were improved, and the development of ovary stroma and small yellow follicle was promoted when the dietary ME levels was 11.72 MJ·kg^-1 from 8 to 18 weeks of age. But no significant difference was observed in the indexes of growth performance and development among the treatments at the initiation of the laying period (20 weeks of age). The results of the present study showed that it has an important practical importance to study the combination of growing period and preparatory laying period of laying hens.