Effect of select tannin sources on pathogen control and microbial nitrogen metabolism in composted poultry litter intended for use as a ruminant crude protein feedstuff

Authors: ARZOLA-ALVAREZ, CLAUDIO - Universidad Autonoma De Chihuahua; Anderson, Robin; Hume, Michael; LEDEZMA, EVELYN - Universidad Autonoma De Chihuahua; RUIZ-BARRERA, OSCAR - Universidad Autonoma De Chihuahua; CASTILLO-CASTILLO, YAMI - Universidad Autonoma De Chihuahua; ARZOLA-RUBIO, ALEJANDRO - Universidad Autonoma De Chihuahua; ONTIVEROS, MARINA - Universidad Autonoma De Chihuahua; MIN, BYENG - Tuskegee University; WOTTLIN, LAUREN - Non ARS Employee; COPADO, RAMON - Universidad Autonoma De Nuevo Leon; SALINAS-CHAVIRA, JAMIE - University Of Tamaulipas

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2022
Publication Date: 6/21/2022
Citation: Arzola-Alvarez, C., Anderson, R.C., Hume, M.E., Ledezma, E., Ruiz-Barrera, O., Castillo-Castillo, Y., Arzola-Rubio, A., Ontiveros, M., Min, B., Wottlin, L.R., Copado, R., Salinas-Chavira, J. 2022. Effect of select tannin sources on pathogen control and microbial nitrogen metabolism in composted poultry litter intended for use as a ruminant crude protein feedstuff. Frontiers in Veterinary Science. 9. Article 930980. https://doi.org/10.3389/fvets.2022.930980.
DOI: https://doi.org/10.3389/fvets.2022.930980

Interpretive Summary: Poultry litter contains a nitrogen-containing chemical called uric acid which makes it a good crude protein supplement for cattle and for use as a fertilizer. However, poultry litter should be treated to kill pathogens before feeding to ruminants or applying to land. Composting effectively kills pathogens in poultry litter, but the process leads to the loss of usable nitrogen due to biodegradation of uric acid which subsequently becomes volatilized, or by being leached away as ammonia. Because tannins possess antimicrobial activity and can inhibit uric acid metabolism, we tested the ability of several tannin sources to preserve uric acid and reduce pathogens during poultry litter composting. In two separate experiments, poultry litter was prepared for composting in the laboratory and treated with or without pine bark, quebracho, chestnut, or mimosa tannins. The composts were also inoculated with a pathogenic bacterium called Salmonella Typhimurium and then composted for 9 days. The first experiment tested tannin addition at about 1 g/100 g litter, and found that after 6 days of composting, numbers of the challenge Salmonella were about 10-fold lower in quebracho-treated composts compared to numbers in untreated control composts. After 9 days of composting, numbers of the challenged Salmonella, indigenous Escherichia coli, and indigenous total culturable aerobic bacteria in untreated and all tannin-treated composts were decreased more than 100-fold when compared to initial numbers at the start of the experiment. This indicated the composting treatment was inhibiting the bacteria with or without the addition of tannins. However, concentrations of uric acid, urea, and ammonia were all higher after 9 days of composting than at the start of the first experiment indicating the tannins were helping to preserve the nitrogen content of the composted poultry litter. In the second experiment, accumulations of uric acid were higher, and concentrations of ammonia were lower in most of the tannin-treated composts after 24 h and 9 days composting. This indicated the tannin treatment can help preserve the nitrogen content of the composting litter. Results provide evidence that composting can be an effective pathogen control technology and that tannin treatment can help preserve the crude protein quality of composting poultry litter. These findings may ultimately lead to the development of a safe, environmentally compatible, and sustainable technology to recycle valuable nutrients contained in poultry litter. The development of a safe and effective low-cost technology to kill unwanted bacteria while preserving nutrient quality is consistent with good agricultural practices and will allow livestock producers to produce wholesome foods at less cost for the American consumer.

Technical Abstract: Poultry litter contains uric acid which makes it a good crude protein supplement for ruminants. However, poultry litter must be treated to kill pathogens before feeding. Composting effectively kills pathogens but risks loss of ammonia due to uric acid degradation. Because tannins possess antimicrobial activity and can inhibit uric acid metabolism, we tested their ability to preserve uric acid and reduce pathogens during poultry litter composting. In two separate experiments, used poultry litter (76 and 98% dry matter, respectively) was mixed with 0.4 M phosphate buffer (pH 6.5) and distributed to 50-mL tubes (3/treatment per sample day) amended with 1 mL of buffer alone or buffer containing pine bark, quebracho, chestnut, or mimosa tannins to achieve 0.63% wt/wt (experiment 1) or 4.5% pine bark or 9% quebracho, chestnut or mimosa tannins(experiment 2) litter dry matter. Tubes were inoculated with a novobiocin- and nalidixic acid-resistant Salmonella Typhimurium, closed with caps, and incubated at successive 3-day increments at 22C, 37C and 42C, respectively. In experiment 1, an analysis of variance of bacterial numbers enumerated in contents collected on days 0, 6, and 9 revealed treatment by day effect (P < 0.03) on the challenged Salmonella, with numbers being 1.0 log10 CFU units lower in quebracho-treated composts than in untreated controls after 6 days of composting. After 9 days of composting, numbers of the challenged Salmonella, indigenous E. coli, and indigenous total culturable aerobes in untreated and all tannin-treated composts were decreased more about 2.0 log10 CFU units when compared to initial numbers at the start of the experiment (3.06, 3.75 and 7.77 log10 CFU/g litter dry matter, respectively). Concentrations of urea and ammonia tended (P < 0.10) to be higher in composts treated by chestnut tannins than in controls and concentrations of uric acid; urea and ammonia were all higher (P < 0.5) after 9 days composting than at the start of experiment 1. Despite applying much higher amounts of tannins in experiment 2, antibacterial effects of treatment or day of composting were not observed (P > 0.05) which was likely due to differences in the quality of the two poultry litter batches. However, treatment x time of composting interactions were observed (P < 0.05) on accumulations of uric acid and ammonia, with quebracho-and chestnut-treated composts being higher in uric acid after 24 h and 9 days composting and chestnut, mimosa, or quebracho-treated composts being lower in ammonia than untreated control composts. Results provided evidence that composting may usually, but not always, be an effective pathogen control technology and that tannin treatment, despite exhibiting little if any antimicrobial activity in the present experiments, can help preserve the crude protein quality of composting poultry litter.