Effect of dietary citric acid, flavomycin and their combination on the performance, tibia ash and immune status of broiler
The goal of this research was to investigate the effect of citric acid (CA), the antibiotic growth promoter flavomycin (FL) and their combination on the growth performance, tibia ash and immune status of broilers. One hundred and sixty straight run day-old broiler chicks (Hubbard Classic) were randomly distributed into four dietary groups, with four replicate cages having 10 birds in each. Standard corn-soybean-based basal starter diet was given to control birds. Diets for other groups were further fortified by 0.5% CA, 0.001% FL and their combination (0.5% CA plus 0.001% FL). On day 35, CA and its combination (CA + FL) group had 17 and 12% increase in live weight compared with control, respectively (P < 0.05). Total live weight on day 35 was 1141, 1337, 1169, and 1275 g bird-1 in different groups, respectively (P < 0.05). Cumulative feed intake was higher (P < 0.05) in CA and its combination (CA + FL) compared with the control and FL groups on day 28. Supplementation with CA improved (P > 0.05) feed conversion ratio [FCR; feed intake (kg):weight gain (kg)] compared with FL and its combination (CA + FL). Carcass yield was increased (P > 0.05) due to the addition of CA and its combination (CA + FL). Tibia ash content in the CA group (59.0) was higher (P < 0.05) than in the control (53.6%), FL (53.1%) and their combination (57.1%). The lymphocyte cells associated with immunity in the lymphoid organs (caecal tonsil, bursa Fabricius and ileum) were more densely populated, suggesting an increased level of innate immunity in the CA group. Overall mortality was low (1.25%), and there were no treatment-related effects on mortality. Citric acid reduced the pH of formulated feeds, but mild reduction was found in the pH of the faeces. Dietary supplementation of 0.5% CA increase weight gain, feed intake, tibia ash deposition and non-specific immunity (P < 0.05) as well as feed efficiency and carcass yield (P > 0.05) of broilers. Citric acid has potential as a growth promoter to replace the antibiotic growth promoter FL.Key words: Citric acid, flavomycin, growth performance, immunity, tibia ash, broiler