饲粮能量和蛋白质水平对滩羊小肠中小肽和氨基酸转运载体mRNA表达量的影响

本试验旨在研究饲粮能量和蛋白质水平对滩羊小肠中小肽和氨基酸转运载体mRNA表达量的影响。选取112只健康、体重相近的滩羊,随机分成4组,每组4个重复,每个重复7只羊。标准水平的饲粮能量和蛋白质水平参考《肉羊饲养标准》(NY/T 816—2004),各组试验滩羊分别饲喂不同能量和蛋白质水平饲粮:0.84×标准水平(Ⅰ组)、0.96×标准水平(Ⅱ组)、1.08×标准水平(Ⅲ组)和1.20×标准水平(Ⅳ组)。试验根据羊体重分2个阶段:29~35 kg和36~40 kg。于每个阶段末,每个重复屠宰1只试验羊,取其小肠组织样,运用实时荧光定量PCR技术,研究小肽转运载体1(Pep T1)、y+型氨基酸转运载体1(CAT1)、兴奋性氨基酸转运载体3(EAAT3)mRNA表达量的变化。结果表明:1)在29~35 kg阶段末,小肠中Pep T1 mRNA的表达量随着饲粮能量和蛋白质水平的提高呈先下降再上升的趋势,Ⅱ组显著低于其他3组(P0.05);Ⅳ组小肠中CAT1 mRNA的表达量显著高于其他3组(P0.05);Ⅲ组小肠中EAAT3mRNA的表达量显著高于其他3组(P0.05)。2)在36~40 kg阶段末,Ⅱ组小肠中Pep T1mRNA的表达量显著高于其他3组(P0.05);Ⅱ组小肠中CAT1 mRNA的表达量显著高于Ⅲ组(P0.05);小肠中EAAT3 mRNA的表达量随着饲粮能量和蛋白质水平的提高呈上升趋势,Ⅲ组和Ⅳ组小肠中EAAT3 mRNA的表达量显著高于Ⅰ组和Ⅱ组(P0.05)。由此可见,饲粮能量和蛋白质水平会影响滩羊小肠中Pep T1、CAT1、EAAT3 mRNA的表达量,使机体对小肽和氨基酸的吸收利用率随之改变,以适应滩羊的生长发育。

Effects of Dietary Energy and Protein Levels on mRNA Expression of Small Peptide and Amino Acid Transporters in Small Intestine of Tan Sheep

This experiment was conducted to study the effects of dietary energy and protein levels on mRNA expression of small peptide and amino acid transporters in small intestine of Tan sheep.A total of 112 healthy Tan sheep with similarly body weight were randomly divided into 4 groups with 4 replicates per group and 7 sheep per replicate.The standard level diet referenced Feeding Standard of Sheep (NY/T 816-2004), sheep in the 4 groups were fed diet with different energy and protein levels diets: 0.84×standard level (group Ⅰ), 0.96×standard level (group Ⅱ), 1.08×standard level (group Ⅲ) and 1.20×standard level (group Ⅳ), respectively.The test period were divided into two stages by body weight of sheep: 29 to 35 kg and 36 to 40 kg.At the end of each stage, one sheep was slaughtered at each replicate, and small intestinal samples were collected to study the expression of peptide transporter 1 (PepT1), y+ cationic amino acid transporter 1 (CAT1)and excitatory amino-acid transporter 3 (EAAT3) mRNA by real-time PCR.The results showed as follows: 1) at the end of 29 to 35 kg stage, the small intestine PepT1 mRNA expression firstly decreased and then increased with diet energy and protein levels increased, and the small intestine PepT1 mRNA expression in group Ⅱ was significantly higher than that in other three groups (P<0.05);the small intestine CAT1 mRNA expression in group Ⅳ was significantly higher than that in other three groups (P<0.05);the small intestine EAAT3 mRNA expression in group Ⅲ was significantly higher than that in other three groups (P<0.05).2) At the end of 36 to 40 kg stage, the small intestine PepT1 mRNA expression in group Ⅱ was significantly higher than that in other three groups (P<0.05);the small intestine CAT1 mRNA expression in group Ⅱ was significantly higher than that in group Ⅲ (P<0.05);the small intestine EAAT3 mRNA expression had a significantly rise trend with diet energy and protein levels increased, and the small intestine EAAT3 mRNA expression in group Ⅲ and group Ⅳ was significantly higher than that in group Ⅰ and group Ⅱ (P<0.05).In conclusion, dietary energy and protein levels can significantly affect the mRNA expression of PepT1, CAT1 and EAAT3 in small intestine of Tan sheep, which can change the absorption and utilization of the small peptides and amino acids to adapt to Tan sheep's growth and development.