| Nutritional and genetic are key factors that affect the growth of animal, GH-IGFs axis play animportent role in regulating growth.In addition, suitable protein levels in diets may contribute tolamb growth.It is very important that growth potential and feed efficiency could be improved byregulating gene expression level with nutrition.This study aims to analyze the effect of threedietary protein levels on growth, IGF-1and GH levels in peripheral blood, IGF-1and GH geneexpression in feed period.The experiment aims to analyze the function on growth, IGF-1, GHsecretion and gene expression with different dietary protein levels, in order to guide sheepproduction and provide the basis for high-quality meat sheep breeding and efficient farming ofsheep.Exp.16-month-old prolific Suffolk sheeps were fed by three protein levels (15%,18%and21%) with equal energy diets after30d,60d,90d and120d four stages respectively.The resultshowed average lamb weight and daily weight gain were significantly correlated with proteinlevels (P<0.05)，there were the best growth and development in high protein group (21%) during120days of feeding period.The body slanting length were significantly affected by protein levelsduring120days of feeding period (P<0.05), the body length were significantly affected by proteinlevels during the entire feeding period (P<0.01).Exp.2IGF-1and GH levels in peripheral blood of lambs were detected in four growth stageswith feeding different protein levels by ELISA method in lamb.The results showed IGF-1concentration consistented with protein levels of control group and high-protein group in the fourstages.IGF-1concentration were increased in control group and high-protein group, however,IGF-1concentration was decreased in low-protein group, the trend of IGF-1concentrations werehigh-protein group, control group, low-protein group in descending order. GH concentration wasincreased in low-protein group, simultaneously, decreased in control group and high-protein group.GH concentration was the highest of120days of feeding period in low-protein group, GHconcentration were low-protein group, control group, high-protein group in descending order. GHlevels in high-protein group significantly lower than in low-protein group during60days offeeding period (P>0.05).The relative gene expression of IGF-1and GH gene were analyzed by SYBR Green real-time PCR during four growth stages with three protein levels.The results showed IGF-1and GHgene were expressed in lymph nodes, heart, liver, pituitary gland, brain, kidney, skeletal muscle,skin, lung, testis and spleen of sheep, IGF-1gene expression level was the highest in the liver, GHgene expression level was the highest in the spleen. It was indicated IGF-1gene expressed in theliver.GH gene has pleiotropism.The IGF-1gene expression level was high-protein group, controlgroup, low-protein group in descending order in four lamb growth stages. IGF-1gene expressionin high-protein group was significantly higher than low-protein group in60days of feeding period (P<0.05), IGF-1gene expression in high-protein group and control group were significantlyhigher than low-protein group in120days of feeding period (P<0.05).GH gene expression levelswas not change significantly in four stages.Exp.3There was C.364G>A base conversion, GG and GA genotypes in GH gene, andC.153T>C base conversion, TT, CC and CT genotypes in IGF-1gene by using gene cloning,sequencing and Squenom MassARRAYP technology platform in sheep population.The C.364G>Asite of GH gene did not affect sheep average birth weight, weaning weight and1-year-old bodyweight by least squares regression model (LSM)(P>0.05);1-year-old body weight of TTgenotype individuals of IGF-1gene was significantly higher than CC and CT genotypesindividuals (P <0.05), TT genotype could be used to select fast-growing sheeps. |
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