中国农业科学 ›› 2020, Vol. 53 ›› Issue (23): 4950-4960.doi: 10.3864/j.issn.0578-1752.2020.23.019

• 畜牧·兽医·资源昆虫 • 上一篇    下一篇

日粮中添加小肽对育肥牦牛生产性能和消化道PepT1 mRNA表达的影响

苗建军(),彭忠利(),高彦华,柏雪,谢昕廷   

  1. 西南民族大学畜牧兽医学院/青藏高原动物遗传资源保护与利用教育部重点实验室,成都 610041
  • 收稿日期:2019-12-11 接受日期:2020-05-12 出版日期:2020-12-01 发布日期:2020-12-09
  • 通讯作者: 彭忠利
  • 作者简介:苗建军,E-mail: 332779037@qq.com
  • 基金资助:
    国家重点研发计划(2017YFC0504806);国家现代农业产业技术体系四川省肉牛创新团队(sccxtd-2020-13);四川省重点研发项目(2017NZ0042)

Effects of Dietary Small Peptides on Production Performance and Expression of PepT1 mRNA in Digestive Tract of Fattening Yaks

MIAO JianJun(),PENG ZhongLi(),GAO YanHua,BAI Xue,XIE XinTing   

  1. College of Animal and Veterinary Sciences, Southwest Minzu University/Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Chengdu 610041
  • Received:2019-12-11 Accepted:2020-05-12 Online:2020-12-01 Published:2020-12-09
  • Contact: ZhongLi PENG

摘要:

【目的】研究日粮中添加小肽对育肥牦牛生产性能、养分表观消化率、血液指标及消化道小肽转运载体1(PepT1)mRNA表达的影响,为小肽在牦牛日粮中的合理应用提供数据支持。【方法】选取36头体重((180.98±20.57)kg)相近,健康的麦洼公牦牛,按照随机区组试验设计分为4组,每组9个重复,每个重复1头牛。分别饲喂小肽添加水平为0、0.75%、1.50%、2.25%的全混合日粮。预饲期30 d,正试期80 d。试验开始和结束时记录体重,每日饲喂时记录每头牦牛的喂料量及剩料量。试验最后一周,连续3 d收集每头牦牛的饲料及粪便样品,进行常规营养分析;同时,每组选取5头牦牛采集颈静脉血并制备血清,测定血清生化及免疫指标。试验结束后,将每组采血的5头牦牛屠宰,立即取瘤胃、网胃、瓣胃、皱胃及十二指肠、空肠、回肠组织,通过实时荧光定量PCR法测定各组织中PepT1 mRNA的表达量。【结果】(1)平均日增重(ADG)、干物质采食量(DMI)和料重比(F/G)随小肽添加水平的升高均呈二次曲线变化(P<0.05),以2.25%组牦牛的生产性能表现最优,其DMI和ADG均显著高于对照组和0.75%组(P<0.05),而F/G显著低于对照组和0.75%组(P<0.05)。(2)随小肽添加水平的升高,日粮有机物(OM)和粗蛋白(CP)的表观消化率呈二次曲线上升(P<0.05),中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的表观消化率线性升高(P<0.01),以2.25%组消化率最高;各处理组中钙、磷的表观消化率无显著差异(P>0.05)。(3)随小肽添加水平的升高,血清中谷丙转氨酶(ALT)含量线性降低(P<0.05),而尿素氮(UN)含量线性升高(P<0.05),总蛋白(TP)含量有线性升高的趋势(P<0.10),谷草转氨酶(AST)含量呈二次曲线降低(P<0.05),而碱性磷酸酶(ALP)、葡萄糖(GLU)、胆固醇(CHO)、甘油三酯(TG)含量未产生显著变化(P>0.05);日粮中添加不同水平小肽对牦牛血清中IgG、IgA和IgM三种免疫球蛋白的含量均无显著影响(P>0.05)。(4)牦牛消化道中PepT1 mRNA表达量由高到低依次为空肠、回肠、十二指肠、网胃、瓣胃、瘤胃、皱胃,且空肠PepT1 mRNA的表达量显著高于其他消化道部位(P<0.05),而皱胃PepT1 mRNA的表达量显著低于空肠和回肠(P<0.05);回肠、十二指肠、瘤胃、网胃、瓣胃的PepT1 mRNA表达量无显著差异(P>0.05)。随小肽添加水平的升高,瘤胃、网胃和空肠的PepT1 mRNA表达量均呈线性升高变化(P<0.05),但对瓣胃、皱胃、十二指肠和回肠的PepT1 mRNA表达量均无显著影响(P>0.05)。【结论】日粮中添加小肽能够提高育肥牦牛的生产性能和养分表观消化率,改善肝功能,促进小肽在消化道中的转运吸收。在本试验条件下,日粮小肽添加水平为2.25%时饲喂效果最佳。

关键词: 小肽, 育肥牦牛, 生产性能, 养分表观消化率, 血液指标, PepT1 mRNA表达

Abstract:

【Objective】This study investigated the effects of dietary small peptides on production performance, apparent digestibility of nutrients, blood indexes and expression of PepT1 mRNA in digestive tract of fattening yaks. 【Method】Health Maiwa male yaks (n=36, (180.98±20.57) kg body weight) were divided into 4 groups in a randomized complete block design, and each group had 9 male yaks. And they were fed 4 types of total mixed ratio diet with small peptides additions of 0, 0.75%, 1.50% and 2.25%, respectively. There was a pre-experimental period of 30 days, followed by a trial period of 80 days. Every yak’s weight was recorded before and after the trial begins, and the feed intake was also recorded every day. During the last week of the trial period, the fecal grab samples were collected for 3 consecutive days from each yak for routine analysis of nutrients. And five yaks were selected from each group to collect jugular vein blood and prepare serum to determine serum biochemical and immune indicators. At the end of the trial period, 5 yaks with blood collected were slaughtered, and the rumen, reticulum, omasum, abomasum, duodenum, jejunum, and ileum tissue were collected to determine the expression of PepT1 mRNA by using real time quantitative PCR. 【Result】(1) With the level of small peptides increasing, the dry matter intake, average daily gain and the feed gain ratio showed quadratic variation (P<0.05). The group with the best production performance was the 2.25% group. Compared with the control group and the 0.75% group, the dry matter intake and average daily gain were significant improved in the 2.25% group, but the feed gain ratio was significant decreased in the 2.25% group. (2) With increasing of small peptides levels, the degradation rate of neutral detergent fibre and acid detergent fibre linearly increased (P<0.01); the degradation rate of organic matter and crude protein presented quadratic variation (P<0.05). The 2.25% group had the highest digestibility. No significant difference existed between the degradation rate of calcium and phosphorus in four groups (P>0.05). (3) Across the range of small peptides supplementation levels, the content of alanine aminotransferase linearly decreased (P<0.05); the content of urea nitrogen linearly increased (P<0.05); the total protein showed linearly increased trend (P<0.10), and the content of aspartate aminotransferase showed quadratic variation (P<0.05). There were no significant effects on the content of alkaline phosphatase, glucose, cholesterol, triglyceride and immunoglobulins (IgG, IgA and IgM) in yak serum by adding different levels of small peptides. (4) The expression of PepT1 mRNA in the digestive tract of yaks from the highest to the lowest was the jejunum, ileum, duodenum, reticulum, omasum, rumen, and abomasum, while the expression of PepT1 mRNA in jejunum was significantly higher than that of the other gastrointestinal tracts (P<0.05). The expression of PepT1 mRNA in abdomen was significantly lower than those of jejunum and ileum. No significant difference was found between the expression of PepT1 mRNA in ileum, duodenum, reticulum, omasum, and rumen. With increasing of small peptides levels from 0 to 2.25%, the expression of PepT1 mRNA in rumen, reticulum and jejunum linearly increased (P<0.05), and small peptides levels had no significant effect on the expression of PepT1 mRNA in omasum, abomasum, duodenum and ileum (P>0.05). 【Conclusion】 In conclusion, dietary small peptides could improve the production performance, apparent digestibility of nutrients, liver function of fattening yaks, and promote the transport and absorption of small peptides in the digestive tract. In this research, the appropriate level of dietary small peptides of yaks was 2.25%.

Key words: small peptides, fattening yaks, production performance, apparent digestibility of nutrients, blood indexes, expression of PepT1 mRNA