Dietary alfalfa fiber (AF) is conceived to modulate gut microbial richness and diversity to improve the health and growth of weaning piglets.

Non-fiber carbohydrates (NFC) have a crucial function on the gut health of monogastrics. This paper aims to review the relevant published materials on the influence of NFCs on the gut's microbial population and composition in monogastrics, and points out the areas of the required research. Total bacteria count and Lactobacillus sp. were decreased with an increase in composition of dietary NFC intake, as well as accompanied by a decrease in the short-chain fatty acids (SCFAs) levels. Consequently, some metabolites were affected by the accumulation of the bile acids, including molecules which control different gene expression levels, as regulators involved in glucose (FXR and TGR5) and fat metabolism (cholesterol). Cell proliferation rate of both gastrointestinal epithelium and microbiome cells was negatively correlated with the dietary NFC levels in many species of monogastric animals. Low levels of NFC diet are negatively associated with digestibility, total gut weight, and gastrointestinal secretions. High levels of dietary NFC have negative effects on the digestion and absorption of macronutrients, with an increase of the contact time of the carcinogens in the intestinal lumen. The data obtained from different animals' studies did not give the same results. In conclusion, dietary NFC should be adjusted to the optimal consumption levels as the human and the monogastric animals are anatomically and physiologically different. Digestion, metabolism, host wellbeing, and host behavior were negatively affected by the administration of high NFC levels. The relations between sulphate-reducing bacteria and some metabolic diseases such as diabetes mellitus and obesity need further exploration.