Abstract
Selenium (Se) deficiency is a widespread and seasonally chronic phenomenon observed in Tibetan sheep (Ovis aries) traditionally grazed on the Qinghai–Tibet Plateau (QTP). Effects of the dietary addition of Se-enriched yeast (SeY) on the bacterial community in sheep rumen and rumen fermentation were evaluated with the aim of gaining a better understanding of the rumen prokaryotic community. Twenty-four yearling Tibetan rams [initial average body weight (BW) of 31.0 ± 0.64 kg] were randomly divided into four treatment groups, namely, control (CK), low Se (L), medium Se (M), and high Se (H). Each group comprised six rams and was fed a basic diet of fresh forage cut from the alpine meadow, to which SeY was added at prescribed dose rates. This feed trial was conducted for over 35 days. On the final day, rumen fluid was collected using a transesophageal sampler for analyzing rumen pH, NH3-N content, volatile fatty acid (VFA) level, and the rumen microbial community. Our analyses showed that NH3-N, total VFA, and propionate concentrations in the M group were significantly higher than in the other groups (P < 0.05). Both the principal coordinates analysis (PCoA) and the analysis of similarities revealed that the bacterial population structure of rumen differed among the four groups. The predominant rumen bacterial phyla were found to be Bacteroidetes and Firmicutes, and the three dominant genera in all the samples across all treatments were Christensenellaceae R7 group, Rikenellaceae RC9 gut group, and Prevotella 1. The relative abundances of Prevotella 1, Rikenellaceae RC9 gut group, Ruminococcus 2, Lachnospiraceae XPB1014 group, Carnobacterium, and Hafnia-Obesumbacterium were found to differ significantly among the four treatment groups (P < 0.05). Moreover, Tax4fun metagenome estimation revealed that gene functions and metabolic pathways associated with carbohydrate and other amino acids were overexpressed in the rumen microbiota of SeY-supplemented sheep. To conclude, SeY significantly affects the abundance of rumen bacteria and ultimately affects the rumen microbial fermentation.
Highlights
Rumen, a digestive organ that differentiates uminants from other mammals, is the most efficient natural fermentation system
Our previous study showed that Se-enriched yeast (SeY) could benefit Tibetan sheep by improving nitrogen metabolism and nutrient digestibility (Wang et al, 2019), the effect of Se dose rates on rumen fermentation parameters and microbial communities is still unknown. Considering these Se deficiency-related livestock health and performance problems in the Qinghai–Tibet Plateau (QTP), in the present study, we evaluated the effects of Se dietary supplement administered as SeY on rumen fermentation and bacterial community structure
The addition of SeY in the diet changed the rumen microflora of Tibetan sheep, which eventually affected the levels of volatile fatty acid (VFA) in the rumen fluid
Summary
A digestive organ that differentiates uminants from other mammals, is the most efficient natural fermentation system. In this organ, microorganisms ferment and degrade forage fibers and convert them into digestible proteins and volatile fatty acids (VFAs, the primary energy source for ruminants) for digestion and absorption (Dai et al, 2015). Several studies have shown that rumen microorganisms are closely linked to the ruminant livestock production efficiency and provide the host with as much as 65–75% of its energy requirement through anaerobic fermentation (Jewell et al, 2015; Chen et al, 2020). The rumen microbial community structure is affected by factors such as host type, health, and diet, and it varies across different regions and seasons (Yáñez-Ruiz et al, 2015)
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