Location: Livestock Nutrient Management ResearchTitle: Prevalence of antibiotic resistance genes and bacterial community diversity from feces of pasture-raised broiler and layer chickens, swine, and beef cattle in the Southeastern USA
|Castleberry, Bobbie - Lana|
|Brauer, David - Dave|
|PITTA, D - University Of Pennsylvania|
|INDUGU, N - University Of Pennsylvania|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2020
Publication Date: 7/23/2020
Citation: Min, B., Castleberry, B., Rothrock Jr, M.J., Rutherford, L., Waldrip, H., Parker, D.B., Brauer, D.K., Pitta, D.W., Indugu, N. 2020. Prevalence of antibiotic resistance genes and bacterial community diversity from feces of pasture-raised broiler and layer chickens, swine, and beef cattle in the Southeastern USA [abstract]. 2020 ASAS-CSAS-WSASAS Virtual Annual Meeting and Trade Show. Paper No. PSXI-23.
Technical Abstract: Animal manure can be a source of antibiotic resistant genes (ARGs) and pharmaceutical residues; however, few studies have been conducted to evaluate the presence of ARGs in pastured livestock systems. The objective was to determine the effects of four pasture-raised livestock species (broiler and layer chickens, swine, and beef cattle) on three different farms on fecal antibiotic residues (AR), microbial community diversity (MCD), and ARGs. Fecal DNA was collected (25 g each), homogenized, and extracted (0.2 g) using a Fecal/Soil Microbe DNA MiniPrep Kit. Total 16S rRNA abundances, an estimate of the total MCD, was sequenced in the V4 region. Sulfonamide (Sul; Sul1) and tetracycline (Tet; TetA) ARGs were enumerated by qPCR. The results indicated that average fecal Tet AR tended to be greater (P=0.09) for broiler chickens (11.4 ug/kg) than for other livestock species (1.8-0.06 ug/kg), while chlortetracycline, lincomycin, oxytetracycline, and sulfachloropyridazine AR were similar among livestock species. There were interactions (P<0.01) between farms and animal species for fecal pH and concentrations of total carbon, magnesium, sulfur, copper, and lead across animal species. In addition, cattle and swine samples showed a high degree of variability (alpha- and beta-diversities) in fecal MCD, compared to broiler and layer fecal samples (P<0.01). Firmicutes were the most abundant bacterial phylum in broiler (85.3 percent) and layer (80.0 percent) chickens (P<0.01), as compared to swine (64.4 percent) and cattle (62.1 percent). The Sul1 (P<0.05) and TetA (P<0.001) ARGs in layer hens were the highest (16.5E-4 and 1.4E-4), followed by broiler chickens (2.9E-4 and 1.7E-4), swine (0.22E-4 and 0.20E-4), and beef cattle (0.19E-4 and 0.02E-4). This study indicated that individual farm management practices and specific animal species affected content of fecal AR, the fecal MCD, and ARG status in pasture-raised animals.