Effect of a low protein diet on chicken ceca microbiome and productive performances.

The aim of this study was to investigate the impact of supplementation of a low protein diet on ceca microbiome and productive performances of broiler chickens. A total of 1,170 one-day-old male chicks (Ross 308) were divided in 2 diet groups and reared in the same conditions up to 42 D. Birds belonging to the control group were fed a basal diet. Birds belonging to the low protein group the basal diet with a reduced level of crude protein (-7%). Cecum contents from randomly selected birds were collected at 14 and 42 D within each diet group, submitted to DNA extraction and then tested by shotgun metagenomic sequencing. Abundances of species belonging to Actinobacteria and Proteobacteria were mainly affected by the diet as well as interaction between diet and time, while species belonging to Firmicutes and Cyanobacteria changed mainly according to the age of the birds. At family level, Lactobacillaceae significantly decreased in the low protein group up to 14 D. However, at the end of the rearing period the same family was significantly higher in the low protein group. The most abundant functional genes, represented by cystine desulfurase, alpha-galactosidase, and serine hydroxymethyltransferase, displayed comparable abundances in both diet groups, although significative differences were identified for less abundant functional genes at both sampling times. Birds fed control and low protein diets showed similar productive performances. However, in the finisher phase, feed conversion rate was significantly better in chickens fed the low protein diet. Overall, this study showed that a reduced intake of crude protein in broilers increases the abundance of Lactobacillaceae in the ceca over time and this seems to be linked to a better feed conversion rate between 36 and 42 D. A reduced intake of crude protein in chicken production can help to improve exploitation of edible resources, while reducing the emission of nitrogen pollutants in the environment.