Evaluation of humic acids as functional feed additive on performance, metabolic parameters and gut microbiota of weaned piglets.

Humic acids (HA), originated from the decomposition of organic matter in the soil by microorganisms, have been recently added in the European catalogue of feed materials considering for their therapeutic effects on gastrointestinal diseases. In swine livestock, there is an urgent need of alternatives to antibiotics. Since the data present in literature are scarce and HA nutritional value is not well-defined, the aim of this study was to evaluate the in vivo effect of HA as functional dietary feed supplement in weaned piglets. One-hundred twenty weaned piglets (28±2 days) were randomly divided into two groups fed control diet (CON) and HA enriched diet (0.25%; HAG). Zootechnical parameters were measured during the entire experimental period (40 days). On individual faecal samples, gut microbiota composition was obtained by sequencing the V3-V4 regions of the 16S rRNA gene. Principal blood parameters were analysed by auto-analyser on individually collected serum (total protein content, albumin, globulin, albumin/globulin, urea, alanine aminotransferase, aspartate aminotransferase, phosphatase alkaline, total bilirubin, glucose, total cholesterol, calcium, phosphorus, magnesium, total triglycerides, high-density lipoproteins, low-density lipoproteins and creatinine). Obtained results showed an increase of zootechnical performances (body weight, average daily gain, average daily feed intake) (p < 0.001) of the HAG compared to CON. The serum metabolic profile highlighted a decrease of total triglycerides (p < 0.05) with a higher content of cholesterol (p < 0.05) but only high-density lipoprotein revealed a rise (p < 0.001). An increase of observed species (p = 0.01) and Shannon’s index (p = 0.03) was observed in HAG. Concerning β diversity, principal coordinate analysis (PCoA) plots revealed no distinct separation of samples. However, only a significant increase of Prevotella (p = 0.035) was detected indicating a very limited impact of this supplementation on intestinal microbiota.