Changes in Carbohydrate Composition in Fermented Total Mixed Ration and Its Effects on in vitro Methane Production and Microbiome.

Yang Li,Shuang Zhou,Yaxue Lan,Jingyi Lv,Yukun Sun,Guangning Zhang,Yonggen Zhang,Bingdong Wei,Jihong Wang,Xiujing Dou

doi:10.3389/fmicb.2021.738334

Abstract

The purpose of this experiment was to investigate the changes of carbohydrate composition in fermented total mixed diet and its effects on rumen fermentation, methane production, and rumen microbiome in vitro. The concentrate-to-forage ratio of the total mixed ration (TMR) was 4:6, and TMR was ensiled with lactic acid bacteria and fibrolytic enzymes. The results showed that different TMRs had different carbohydrate compositions and subfractions, fermentation characteristics, and bacterial community diversity. After fermentation, the fermented total mixed ration (FTMR) group had lower contents of neutral detergent fiber, acid detergent fiber, starch, non-fibrous carbohydrates, and carbohydrates. In addition, lactic acid content and relative abundance of Lactobacillus in the FTMR group were higher. Compared with the TMR group, the in vitro ammonia nitrogen and total volatile fatty acid concentrations and the molar proportion of propionate and butyrate were increased in the FTMR group. However, the ruminal pH, molar proportion of acetate, and methane production were significantly decreased in the FTMR group. Notably, we found that the relative abundance of ruminal bacteria was higher in FTMR than in TMR samples, including Prevotella, Coprococcus, and Oscillospira. At the same time, we found that the diversity of methanogens in the FTMR group was lower than that in the TMR group. The relative abundance of Methanobrevibacter significantly decreased, while the relative abundances of Methanoplanus and vadinCA11 increased. The relative abundances of Entodinium and Pichia significantly decreased in the FTMR group compared with the TMR group. These results suggest that FTMR can be used as an environmentally cleaner technology in animal farming due to its ability to improve ruminal fermentation, modulate the rumen microbiome, and reduce methane emissions.

Highlights

Methane is a greenhouse gas with an abundance second only to carbon dioxide, and the greenhouse efficiency is 25 times that of the equivalent amount of carbon dioxide (IPCC, 2007), which can enhance radiative forcing and greenhouse effects, and further aggravate disasters such as climate deterioration, global warming, and land desertification
Our previous studies proved that Fermented total mixed ration (FTMR) could improve the feed efficiency and lactation performance of dairy cows (Zhang et al, 2020b); we discovered that the contents of structural carbohydrates (NDF and acid detergent fiber (ADF)) in FTMR were significantly reduced with an increased lactic acid content (Zhang et al, 2020a,b)
The fractions of CA1 (P = 0.002) and CC (P = 0.01) in total mixed rations (TMR) increased significantly after fermentation (Table 2). This indicates that fermentation improves the availability of carbohydrates in TMR. It can be seen from the results of this experiment that the changes in carbohydrate composition of TMR by cofermentation of lactic acid bacteria and cellulose enzymes are obvious, which lay a foundation for the change in rumen fermentation type and the reduction in methane production

Summary

Introduction

Methane is a greenhouse gas with an abundance second only to carbon dioxide, and the greenhouse efficiency is 25 times that of the equivalent amount of carbon dioxide (IPCC, 2007), which can enhance radiative forcing and greenhouse effects, and further aggravate disasters such as climate deterioration, global warming, and land desertification. Whether from the perspective of environmental protection or animal production, it is extremely necessary to reduce methane emissions from ruminants. Methane reduction is an important research topic in the field of ruminant nutrition and in environmental protection. Methane emissions can be reduced through dietary manipulation and feed additives. Ionophore antibiotics (monensin) have been banned in the production of heifers and dairy cows in some countries. It is a safer and more effective method to reduce methane production by using ruminant diet nutrition control methods

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Conclusion