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Animal manure can be a source of antibiotic resistant genes (ARG) and pharmaceutical residues; however, few studies have evaluated the presence of ARG in pasture-raised animal production systems. The objective of this study was to examine changes in microbiome diversity and the presence of antibiotic residues (ABR) on three farms that contained a diverse range of animal species: pasture-raised poultry (broiler and layer), swine and beef cattle. Total bacterial communities were determined using 16S rRNA microbiome analysis, while specific ARG (sulfonamide [Sul; Sul1] and tetracycline [Tet; TetA]) were enumerated by qPCR. Results indicated that the ARG abundances (Sul1 [P < 0.05] and TetA [P < 0.001]) were higher in layer hen manures (16.5 x 10 -4 and 1.4 x 10 -4 µg kg -1, respectively) followed by broiler chickens (2.9 x 10 -4 and 1.7 x 10 -4 µg kg -1, respectively), swine (0.22 x 10 -4 and 0.20 x 10 -4 µg kg -1, respectively) and beef cattle (0.19 x 10 -4 and 0.02 x 10 -4 µg kg -1, respectively). Average fecal TetA ABR tended to be greater (P = 0.09) for broiler chickens (11.4 µg kg -1) than for other animal species (1.8-0.06 µg kg -1), while chlortetracycline, lincomycin, and oxytetracycline ABR were similar among animal species. Furthermore, fecal microbial richness and abundances differed significantly (P < 0.01) both among farms and specific species of animal. This study indicated that the microbial diversity, ABR, ARG concentrations, and types in feces varied from farm-to-farm and from animal species-to-animal species. Future studies are necessary to perform detailed investigations of the horizontal transfer mechanism of antibiotic resistant microorganisms (ARM) and ARG.

Ruminal methane (CH4) production results from carbohydrate fermentation by ruminal microbiota (methanogens) to produce CH4, volatile fatty acids (VFA), carbon dioxide (CO2), nitrous oxide (N2O), and hydrogen (H2) in a reduction pathway. The aims of this study were to assess the effects of two red seaweed (RSW) species (Asparagopsis taxiformis and A. armata; collected from Messina, Italy). The two RSW were identified by DNA barcoding and genetic data were deposited in BOLD Systems (REAPP006-21, REAPP004-21, respectively). The two RSW were used at dietary inclusion levels (0, 2, and 4% as-fed basis) in an anaerobic in vitro study (39°C for 48-h) to examine greenhouse gas (GHG) production and VFA profiles. Gases were collected using an ANKOM Gas Production system and analyzed for CH4 and N2O by gas chromatography. Asparagopsis taxiformis contained higher levels of bromoform (201 vs. 7.0 mg/kg DM), iodine (4820 vs. 3260 ppm), and crude protein (16 vs. 15.6% DM), than A. armata, which contained higher levels of acid detergent fiber (ADF; 7.7 vs. 19.0%) and neutral detergent fiber (NDF; 13.2 vs. 19.2%), respectively. RSW supplementation increased total gas, butyrate and valerate production (P < 0.01), while production of CH4 (mg/g DM), acetate (A), propionate (P), A/P ratios and in vitro dry matter digestibility (IVDMD; % DM) were reduced (P < 0.01) as RSW supplementation increased. In the presence of A. taxiformis, production of N2O (µg/g DM), tended to be less (P = 0.1) at 2% DM, but increased (P < 0.01) N2O production with A. armata at the 2 and 4% DM. Therefore, it may be possible to suppress methanogenesis both directly and indirectly by addition of RSW. To efficiently use seaweeds as feed ingredients with nutritional and environmental benefits, more research is required to determine the mechanisms underlying seaweed and dietary substrate interactions.