A Moderate Reduction of Dietary Crude Protein Provide Comparable Growth Performance and Improve Metabolism via Changing Intestinal Microbiota in Sushan Nursery Pigs

SIMPLE SUMMARY: Dietary protein is an important source of amino acids for livestock, while excess protein consumption and an imbalance of amino acids in the diet result in increased feed costs and an increased risk of diarrhea, caused by the proliferation of pathogenic bacteria. Therefore, we investigated whether a diet with a moderate reduction of crude protein levels, supplemented with crystalline amino acids, could alleviate these problems. The results showed that a moderate reduction in the dietary protein level can provide similar growth performance and improve metabolism, due to the improvement of intestinal microbiota, compared with high protein feed in Sushan nursery pigs. These findings present new insights into the role of microorganisms in metabolism, and point to a potential nutrition strategy for indigenous pig production. ABSTRACT: In this paper, we investigated the effects of a diet with a moderate reduction of dietary crude protein (CP) level, supplemented with five crystalline amino acids (Lys, Met, Thr, Try, and Val), on the growth, metabolism, and fecal microbiota of Sushan nursery pigs. Seventy Sushan nursery pigs with an average body weight of 19.56 ± 0.24 kg were randomly allocated to two experimental dietary treatments: 18% CP (high protein; group HP), and 15% CP (low protein; group LP). We found that the differences in the two diets had no significant effect on the growth performance of Sushan nursery pigs. Nursery pigs on the 15% CP diet showed significantly improved protein, amino acid, and energy utilization. Furthermore, the LP diet cloud optimized the gut microflora composition to some extent. The functional structure of bacterial communities implied improved metabolic capabilities in group LP. Additionally, correlation analysis between fecal microbiota and metabolic profiles confirmed that the increase of beneficial bacterial in the feces was beneficial to the health and metabolism of the nursery pigs. In conclusion, a moderate reduction in the dietary protein level can improve growth and metabolism due to the improvement of intestinal microbiota in Sushan nursery pigs. This finding could provide useful reference data for the application of a different nutrition strategy in indigenous pig production.