The use of organic acids in animal nutrition

Abstract

During the last years there has been reported an increase in the use of organic acids as feed additives, which puts them at the center of scientific attention. The European ban of antibiotic growth promoters in 2006, in order to avoid the risk of developing cross-resistance of pathogens, but also to avoid their residues in meet, led to the need for finding the alternative supplements to replace the antibiotics. Among others (enzymes, probiotics, prebiotics, herbs, essential oils, immunostimulants…), organic acdis and their salts are pointed out as effective. Organic acids have been used for decades in commercial compound feeds, mostly for feed preservation, because of the decrease of pH value and the buffering capacity as well as antibacterial and antifungal effects in the feed. These effects are also manifested in gastro-intestinal tract, where they inhibit gram-negative indigenous microflora (Salmonella spp., Escherichia coli, Campylobacter jejuni...). Organic acids reduce the pH value by release of hydrogen ions in the stomach, thereby activating pepsinogen to form pepsin consenquently improving protein digestibility (optimum pH for the activity of pepsin is 2,5–3). Further, they improve the digestion of minerals (P, Ca, Mg, Zn) from nutrients, due to the increased enzyme activity at lower pH (microbial phytase) and the formation of soluble complexes of minerals and organic acid anions. Organic acid improve energetic utilization in the intermediate metabolism. While the main action of organic acid in poultry is mainly antimicrobial, in pigs has been shown that short chain fatty acids like acetic, propionic and n-butyric acid in the GIT may increase the proliferation of epithelial cells and have stimulatory effects on both endocrine and exocrine pancreatic secretions. Lack of consistency in demonstrating an organic acid benefit in poultry is related to the fact that organic acids are rapidly metabolised in the craw, which reduces their impact on growth performances of broilers, but also on layer performances (egg production, egg quality).