Effects of citric acid supplementation on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in steers

Abstract BACKGROUND: An increase feed efficiency and rate of gain were observed from addition of sodium citrate to the diet of fatting lamb. It is suggested that the small amounts of citric acid (CA) may have a catalytic effect on rumen microbial metabolism which would result in a potential means of increasing feed efficiency. The objective was to evaluate the effects of CA supplementation on rumen fermentation, ruminal microbial production by measuring urinary excretion of purine derivatives, and digestibility in the total tract of steers. RESULTS: Ruminal pH linearly ( P = 0.01) decreased, whereas total volatile fatty acid concentration linearly ( P = 0.01) increased with increasing CA supplementation. Ratio of acetate to propionate linearly ( P = 0.01) increased due to the increase in acetate production. Urinary excretion of purine derivatives was quadratically ( P = 0.02) changed, with the lowest for control, medium for low CA and highest for medium and high CA supplementation. Similarly, digestibilities of nutrients in the total tract were also linearly and quadratically increased with increasing dosages of CA. CONCLUSION: Supplementation of CA increased rumen acetate concentration and thus increased ratio of acetate to propionate. Urinary excretion of purine derivatives and total digestibility were improved. In the experimental conditions of this trial, the optimum citric acid dose was about 200 g citric acid per steer per day. Copyright © 2009 Society of Chemical Industry