Effects of Energy-Restricted Feeding during Growing Period on Growth and Development,Hormone Level and Key Genes Involved in Ovarian Steroid Hormone Synthesis of Laying Hens Aged from 6 to 24 Weeks
This experiment was conducted to evaluate the effects of energy-restricted feeding during growing period(6 to 17 weeks of age)on growth and the development,hormone level and key genes involved in ovar-ian steroid hormone synthesis of laying hens aged from 6 to 24 weeks.A total of 720 6-week-old Hy-Line brown laying hens were allocated into 3 groups with 3 replicates per group and 40 laying hens per replicate.During 6 to 17 weeks of age,the laying hens in 3 groups were fed experimental diets with metabolizable energy(ME)levels were 12.34(control group),11.11(90％energy-restricted feeding group)and 9.87 MJ/kg(80％energy-restricted feeding group)and the equal other nutrient levels.During 17 to 24 weeks of age,the laying hens in all groups were fed the same experimental diet.The experiment lasted for 18 weeks.The results showed as follows:1)with the increasing degree of energy restriction during 6 to 17 weeks of age,the body weight,abdominal fat percentage,heart index and tibia weight at 17 weeks of age,and the body weight,ab-dominal fat percentage,femur weight,tibia weight and metatarsal weight at 20 weeks of age were significantly linearly decreased(P＜0.05),the pancreas index at 17 weeks of age,the liver index at 20 weeks of age and the length-to-weight ratio of femur,tibia and metatarsus at 17 and 20 weeks of age were significantly linearly increased(P＜0.05).The development indices of carcass,visceral organ and bones at 24 weeks of age were not affected by energy restriction from 6 to 17 weeks of age(P＞0.05).2)With the increasing degree of ener-gy restriction during 6 to 17 weeks of age,the serum urea nitrogen(UN)content at 24 weeks of age was sig-nificantly linearly decreased(P＜0.05),and the serum high-density lipoprotein(HDL)content was signifi-cantly linearly increased(P＜0.05).The other serum and liver biochemical indexes at 24 weeks of age were not affected by energy restriction from 6 to 17 weeks of age(P＞0.05).3)The plasma progesterone level at 24 weeks of age of 80％energy-restricted feeding group was significantly higher than that of control group and 90％energy-restricted feeding group(P＜0.05).4)In the ovary stroma,there were 36 genes in 80％and 90％energy-restricted feeding groups at 17,20 and 24 weeks of age,in which the mRNA relative expression levels of 26 genes were down-regulated(P＜0.05),and the mRNA relative expression levels of 7 genes were up-reg-ulated(P＜0.05),the up-regulated genes were cAMP responsive element binding protein 1(CREB1)and cy-tochrome P450 hydroxylase 1B1(CYP1B1)in 80％and 90％energy-restricted feeding groups at 17 weeks of age,the CREB1 in 90％energy-restricted feeding group at 24 weeks of age and 3β-HSD in 80％energy-re-stricted feeding group at 20 and 24 weeksof age.In the theca layer of big white follicles,the mRNA relative expression levels of 12 genes in 80％and 90％energy-restricted feeding groups were significantly up-regulated at 20 weeks of age(P＜0.05);there were also 12 genes in the 80％and 90％energy-restricted feeding groups at 24 weeks of age,in which the mRNA relative expression levels of 9 genes were significantly down-regulated(P＜0.05),and the mRNA relative expression level of 1 gene was significantly up-regulated(P＜0.05),which was CREB1 in 80％energy-restricted feeding group at 24 weeks of age.In the theca layer of small yellow follicles,there were 12 genes in 80％and 90％energy-restricted feeding groups at 24 weeks of age,in which the mRNA relative expression levels of 5 genes were down-regulated(P＜0.05),and the mRNA relative expression levels of 3 genes were up-regulated(P＜0.05),which were cytochrome P450 hydroxylase 17A1(CYP17A1),3β-HSD and CYP1B1 in 80％energy-restricted feeding group.In conclusion,the energy-restrict-ed feeding from 6 to 17 weeks of age significantly affect the body weight and development of abdominal fat and bone of laying hens at 17 and 20 weeks of age,but the development of carcass,visceral organ and bones at 24 weeks of age are not affected,and improve the biochemical indexes related to the metabolism of protein and fat to a certain extent at 24 weeks of age;80％energy-restricted feeding from 6 to 17 weeks of age improve the plasma progesterone level,and up-regulate the mRNA relative expression levels of 3β-HSD in ovary stroma,CREB1 in theca layer of big white follicle and CYP17A1,3β-HSD and CYP1B1 in theca layer of small yellow follicle.[Chinese Journal of Animal Nutrition,2024,36(8):4925-4943]
laying hensenergy-restricted feeding during growing periodgrowth and developmentbiochem-ical indiceshormone levelkey genes involved in ovarian steroid hormone synthesis
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维普
