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 chip-based 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 Salmo-nella typhimurium (STNN) to achieve 3.0 log10 CFU/g and incubated at 37oC 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 µmol/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.

摘要 为探究松树皮单宁在家禽垫料堆肥过程中的抗菌活性与尿酸保留效果，本实验将无抗生素木基家禽垫料（11 g）分装至50 mL锥形离心管中，随即分别添加1.3 mL 0.4 M磷酸钠缓冲液（对照组），或1.3 mL源自长叶松（Pinus palustris）的松皮缩合单宁（水溶液中单宁质量体积分数为9%）。所有实验组（每组设置3个平行管）均接种耐新生霉素与萘啶酸的鼠伤寒沙门氏菌（Salmonella typhimurium，简称STNN），使接种浓度达到3.0 log₁₀ 菌落形成单位（Colony-Forming Unit，CFU）/克，随后于37℃下培养3天以模拟初始堆肥阶段。分别于第0天与第3天检测野生型大肠杆菌、攻毒用STNN菌株的菌落数，以及氨、尿酸与尿素的浓度。与对照组相比，松树皮单宁处理组的垫料中STNN菌落数显著降低（p<0.01），降幅达0.6 log单位。野生型大肠杆菌的菌落数不受单宁处理影响（p>0.05）。单宁处理组垫料中的氨积累量较对照组降低23%（p<0.01），为2.8 ± 0.1 µmol/g。与之相反，松树皮单宁处理组垫料中的残留尿酸浓度较对照组高1.6倍（p=0.02）。尿素浓度不受单宁处理影响（p>0.05）。实验结果表明，松树皮单宁处理可在堆肥垫料中保留尿酸、减少氨挥发，同时有助于沙门氏菌的防控。