Dietary corn-resistant starch suppresses broiler abdominal fat deposition associated with the reduced cecal Firmicutes

This study investigated the effects of dietary corn-resistant starch on lipid metabolism of broilers and its potential relationship with cecal microbiota modulation. A total of three hundred twenty 1-day-old male broilers were randomly assigned into 5 dietary treatments: 1 normal corn–soybean (NC) diet, 1 corn–soybean–based diet supplementation with 20% corn starch (CS), and 3 corn–soybean–based diets supplementation with 4, 8, and 12% corn resistant starch (RS) (identified as 4%RS, 8%RS, and 12%RS, respectively). Each group had 8 replicates with 8 broilers per replicate. The experiment lasted 21 d. The results showed that the abdominal fat percentage were lower in birds from 8%RS and 12%RS groups (0.75 and 0.58%, respectively) than those from NC and CS groups (1.20 and 1.28%, respectively; P < 0.05). The birds from 8%RS and 12%RS groups exhibited lower concentrations of blood triglyceride and nonestesterified fatty acid than those in the NC and CS groups (P < 0.05). Moreover, birds fed diets supplementation with 12% RS decreased the relative mRNA expressions of peroxisome proliferator-activated receptor gamma, ATP citrate-lyase, fatty acid synthase, and acetyl-CoA carboxylase in liver, and glycerol-3-phosphate acyltransferase in abdominal adipose tissue (P < 0.05). Microbiota analysis revealed that birds fed diets supplementation with 8 and 12% RS decreased the abundance of cecal Firmicutes by 23.08 and 20.47% and increased the proportion of Bacteroidetes by 24.33 and 21.92%, respectively, compared with the NC group (P < 0.05). In addition, correlation analysis revealed that many Firmicutes members had highly positive relationship with blood lipid levels and fat storage capacity, which might contribute to the lower abdominal fat phenotype. Overall, broilers receiving diets containing a higher concentration of RS harbor less Firmicutes, which decreased liver fatty acid synthesis and suppress abdominal fat deposition of birds during the starter phase. These findings provide a profound understanding about the relationship between gut microbial composition and lipid metabolism in broilers.