Effects of Dietary Energy Levels on Rumen Fermentation, Gastrointestinal Tract Histology, and Bacterial Community Diversity in Fattening Male Hu Lambs.

Qiye Wang,Mingzhi Zhu,Huansheng Yang,Pengfei Huang,Xianglin Zeng,Yutong Zeng,Yancan Wang,Chunpeng Dai,Xin Wang,Jing Huang,Jianzhong Li,Tarique Hussain

doi:10.3389/fmicb.2021.695445

Abstract

This study investigated rumen fermentation and histological and microbial diversity in male Hu lamb fed diets with different metabolizable energy (ME) levels (MEA, 9.17 MJ/kg, MEB, 10.00 MJ/kg, and MEC, 10.82 MJ/kg). Thirty-six male Hu lambs were randomly allotted to three treatments, and the feeding trial lasted for 67 days. Rumen fermentation results suggest that the iso-valerate had a significant effect on dietary energy level. The papillary height (PH) of rumen was the highest in the MEB group, the crypt depth (CD) was significantly increased in the duodenum and jejunum, and the villus height (VH)-to-CD ratio (VH/CD) was significantly decreased in the duodenum by increasing dietary energy levels; the VH, villus width (VW), and VH/CD also had significant differences in the ileum. 16S rRNA sequencing results showed that the operational taxonomic units (OTUs) number, the ACE, and Chao1 indices were linearly decreased by increasing dietary energy level; 24 phyla including 124 genera were identified, and the relative abundance of Papillibacter and Quinella linearly decreased by increasing the dietary energy level. Compared to MEA and MEB groups, the relative abundance of unidentified_Veillonellaceae and Anaerovibrio was significantly increased in the MEC group at the genus level. The relative abundance of the carbohydrate metabolism pathway predicted by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was linearly increased by increasing the dietary energy levels. Three metabolic pathways identified in Kyoto Encyclopedia of Genes and Genomes (KEGG) level 3 were significantly influenced as the dietary energy level increased. In summary, these results demonstrated that the dietary energy levels affected the rumen fermentation parameters, morphological structures of the gastrointestinal tract (GIT), and the composition and function of rumen microflora in male Hu sheep.

Highlights

The Hu sheep is a unique breed native to China, and is one of the several white lamb-skin sheep breeds in the world (Wang et al, 2020a)
There was no significant difference linearly in the concentrations of acetate, propionate, butyrate, iso-butyrate, iso-valerate, valerate, and total VFA (TVFA), and the ratio of acetate/propionate (Ac/Pr) in the rumen of fattening male Hu lambs with the increase of dietary energy level
Our previous research has found that the daily weight gain (ADG) and dry matter intake (DMI) are significantly increased, and feed conversion ratio (FCR) is dramatically decreased by increasing the dietary ME level in growth performance (Wang et al, 2020a)

Summary

Introduction

The Hu sheep is a unique breed native to China, and is one of the several white lamb-skin sheep breeds in the world (Wang et al, 2020a). Hu sheep are identified as an ideal choice for factory production in our country, especially in southern agricultural areas (Wang et al, 2020b). With the deterioration of ecological environments and the increasing demand for consumption of lamb, ruminant production with traditional grazing patterns is dominated instead by large-scale farming with stall-feeding. As ruminant farming patterns have transformed, animal diets are witnessing a change. Performance traits such as daily gain and rumen micro-ecosystem have changed

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Results

Discussion

Conclusion