Productive performance, gut morphometry, and nutrient digestibility of broiler chicken in response to low and high dietary levels of citric acid

Two experiments were conducted to evaluate the effects of dietary citric acid (CA) on productive performance, gut morphometry, and nutrient digestibility in broiler chickens. In Experiment 1, 200 7-day-old male Ross 308 broiler chicks were used to examine the effects of 0, 10, 20, and 30 g/kg CA up to day 42 of age in 5 replicates of 10 birds each. In Experiment 2, 90 7-day-old male Ross 308 broiler chicks were used to investigate the effects of 0, 30, and 60 g of CA per kg of diet in 3 replicate of 10 birds each up to day 42 of age. In both experiments, inclusion of 30 g/kg of CA increased proventriculus, gizzard, and ileum weight percentage and villus length, crypt depth, and goblet cell number in the duodenum, jejunum, and ileum compared to control birds. Ileal digestibility of crude protein (CP), apparent metabolizable energy (AME), and total phosphorus (tP) were improved. In Experiment 2, administration of CA at 60 g/kg of the diet significantly reduced ileal digestibility of CP, AME, and tP at 30 d of age (P < 0.01). Data obtained from these experiments demonstrated that addition of 30 g/kg of CA to the diet improved almost all zootechnical indices as well as nutrient retention in broiler chicken. In contrast, an increased level of CA up to 60 g/kg resulted in retarded growth and suppressed nutrient digestibility despite the stimulatory effect on gut morphometry and absorbing surface.