Effects of dietary digestible energy levels on growth performance, intestinal function, carcass traits, meat quality and blood biochemical parameters of Ningxiang pigs

The purpose of this study was to explore the effects of changing the digestible energy (DE) level of the diet on the growth performance, intestinal function, carcass traits, meat quality and blood biochemical indices of Ningxiang pigs, and to comprehensively identify the lipid molecules in the abdominal fat of Ningxiang pigs through lipidomics technology to evaluate the pork quality. The experiment selected 225 castrated Ningxiang pigs (47.64 ± 0.58 kg) and randomly divided them into 5 groups, with 5 replicates in each group and 9 Ningxiang pigs in each replicate. Diets with DE of 11.34, 11.80, 12.31, 12.82 and 13.31 MJ/kg were fed respectively, and the experimental period was 56 d. The increase in DE significantly increased the average daily gain (ADG) (<i>P</i> < 0.001), gastric juice pH (<i>P</i> = 0.054) and colonic volatile fatty acid content (<i>P</i> = 0.023) of Ningxiang pigs. The increase in ADG was the result of increased lipid deposition with increasing DE. Increasing DE would lead to a downward trend in the redness value of muscle (a∗, <i>P</i> = 0.088) and significantly reduce the stomach weight index (<i>P</i> = 0.006). Increasing DE increased the depth of duodenal crypts (<i>P</i> = 0.002), and reduced the ratio of villus height to crypt depth (<i>P</i> = 0.002). The colonic microbiota was significantly affected by the increase in DE (<i>P</i> < 0.05). Low (11.34 MJ/kg) DE level reduced serum urea nitrogen levels (<i>P</i> = 0.025) and 11.80 MJ/kg DE level significantly increased pancreatic lipase levels (<i>P</i> = 0.007). In addition, lipidomics revealed the differences in the expression patterns of differential lipid molecules in the abdominal fat of Ningxiang pigs and their potential effects on related metabolic pathways. In conclusion, changes in DE levels had significant effects on the growth performance, intestinal function, carcass traits, meat quality and blood biochemical indices in Ningxiang pigs. High-energy diets may result in excessive fattening of Ningxiang pigs.