Influence of Pine Bark Tannin on Bacterial Pathogens Growth and Nitrogen Compounds on Changes in Composted Poultry Litter

Abstract

To study the antimicrobial and uric acid-preserving activity of pine bark tannin on poultry litter composting, antibiotic-free wood chipbased poultry litter was distributed (11 g) to 50-mL conical centrifuge tubes and immediately amended with 1.3 mL0.4 M sodium phosphate buffer (control) or with 1.3 mL condensed tannins from pine bark (Pinus palustris; 9 \% tannin wt/vol in water). All tubes (n = 3 tubes/treatment) were inoculated with a novobiocin and naladixic acid-resistant Salmonella typhimurium (STNN) to achieve 3.0 log(10) CFU/g and incubated at 37 degrees C for 3 days to simulate an initial compost period. Wildtype E. coli and the challenge STNN strain as well as concentrations of ammonia, uric acid and urea were measured on days 0 and 3. Pine bark tannin treatment decreased (p<0.01) STNN populations in the litter by 0.6 log units compared to the controls. Wildtype E. coli populations were unaffected by tannin treatment (p>0.05). Ammonia accumulation decreased (p<0.01) 23\% in tannin-treated litter compared to the control (2.8 +/- 0.1 mu mol/g). Conversely, the residual uric acid concentration was 1.6-fold higher (p=0.02) in litter treated with the pine bark tannin than in the control litter. Urea concentrations were unaffected by tannin treatment (p>0.05). Results suggest that pine bark tannin treatment may preserve uric acid and reduce ammonia volatilization in composted litter while aiding Salmonella control.