Effects of Selenium Supplementation on Rumen Microbiota, Rumen Fermentation, and Apparent Nutrient Digestibility of Ruminant Animals: A Review

Amin Omar Hendawy,Amira Mohammed Ali,Md Aminul Islam,Ayman H Abd El-Aziz,Kan Sato,Haney Samir,Ahmed Elfadadny,Mohamed Mohsen Mansour,Ahmed S Mandour,A B M Rubayet Bostami,Hend A Abdelmageed,Satoshi Sugimura,Rokaia F Ragab

doi:10.3390/fermentation8010004

Abstract

Enzymes excreted by rumen microbiome facilitate the conversion of ingested plant materials into major nutrients (e.g., volatile fatty acids (VFA) and microbial proteins) required for animal growth. Diet, animal age, and health affect the structure of the rumen microbial community. Pathogenic organisms in the rumen negatively affect fermentation processes in favor of energy loss and animal deprivation of nutrients in ingested feed. Drawing from the ban on antibiotic use during the last decade, the livestock industry has been focused on increasing rumen microbial nutrient supply to ruminants through the use of natural supplements that are capable of promoting the activity of beneficial rumen microflora. Selenium (Se) is a trace mineral commonly used as a supplement to regulate animal metabolism. However, a clear understanding of its effects on rumen microbial composition and rumen fermentation is not available. This review summarized the available literature for the effects of Se on specific rumen microorganisms along with consequences for rumen fermentation and digestibility. Some positive effects on total VFA, the molar proportion of propionate, acetate to propionate ratio, ruminal NH3-N, pH, enzymatic activity, ruminal microbiome composition, and digestibility were recorded. Because Se nanoparticles (SeNPs) were more effective than other forms of Se, more studies are needed to compare the effectiveness of synthetic SeNPs and lactic acid bacteria enriched with sodium selenite as a biological source of SeNPs and probiotics. Future studies also need to evaluate the effect of dietary Se on methane emissions.

Highlights

The conversion of carbohydrates that exist in botanical fibers ingested by ruminants is mainly dependent on the activity of the microbial population in the rumen [1]
Se was supplemented to grass as a fertilizer [25]; in another study, Se was provided to animals orally [76]; and in the rest of the studies, Se was mixed with the diet
Rumen-protected sodium selenite (4.8 mg/cow/day) or coated sodium selenite (0.1, 0.2, or 0.3 mg/kg dry matter (DM)) supplementation reduced the molar proportion of butyrate in the rumen of dairy cows compared with non-treatment [26,77]

Summary

Introduction

The conversion of carbohydrates that exist in botanical fibers ingested by ruminants is mainly dependent on the activity of the microbial population in the rumen [1]. Due to the large number of enzymes excreted by these microorganisms, fibrous plant materials and non-protein nitrogen are broken down and changed into nutritious products, primarily volatile fatty acids (VFA) and microbial protein, which promote the production of milk and muscle [2]. Environmental factors such as heat stress, different management strategies (e.g., diets high in fermentable carbohydrates) and improper diets comprising inadequate supply of essential nutrients and/or improper feed formulation alter the composition of the ruminal microbial communities by promoting the propagation of pathogenic microorganisms in the rumen, resulting in a deficient fermentation process [1,4]. These diets promote the propagation of endotoxic bacteria, which is associated with the reduction in the beneficial microflora, local inflammation in the gut, gut dysbiosis, and passage of the toxic bacteria and their metabolites into the systemic circulation to induce remote dysfunctions in various organs [6,7,8,9,10]

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