Effects of Application of Lactobacilli on Lipid Metabolism in Monogastric and Aquatic Animals: Benefits and Underlying Mechanism.

Lipid metabolism disorder is a common physiological problem in monogastric livestock and aquatic animals which easily leads to excessive fat deposition, poor meat quality, and inhibited growth performance, bringing huge economic losses to the aquaculture and livestock industries. Lactobacilli, as core bacteria found in the gut of animals, play a crucial role in growth and health in monogastric animals, mainly including pigs, poultry, and pets, and even in aquatic animals. Nevertheless, existing relevant reviews mostly provide simple descriptive summaries of phenotypic effects, lacking systematic collation of strain-specific differences and multi-level regulatory mechanisms. Moreover, most mechanistic conclusions are predominantly inferred from rodent studies, while the applicability and specificity of these regulatory pathways in target livestock and aquatic animals remain unclear, forming an important research gap. In view of the above deficiencies, this review summarizes the beneficial effects of different lactobacilli on lipid metabolism in monogastric (including swine, poultry and pets) and aquatic animals. Furthermore, we elucidate the underlying mechanisms in different dimensions: short-chain fatty acid-mediated lipid signal transduction, regulation of liver-adipose axis-related genes (PPARs, SREBP-1c, FAS, etc.), and improvement in intestinal barrier function to inhibit lipid absorption. Also, considering the current limitations that existing mechanistic evidence in livestock and aquatic species is insufficient, this review highlights the bottlenecks of current research and proposes future research priorities, including species-specific mechanism verification, strain functional screening and precise application exploration. This study deepens the comprehensive understanding of lactobacillus-mediated lipid metabolism regulation and provides a reliable theoretical reference for the targeted application of lactobacilli in improving lipid metabolic disorders in monogastric animals and aquaculture animals.