The microbiological and biochemical parameters of manure from antibiotic-treated turkeys

Abstract

The microbiological and biochemical parameters of manure should be considered in order to develop comprehensive and effective strategies for the management of manure from farmed antibiotic-treated turkeys in accordance with environmentally sustainable practices, taking into account social and economic aspects. Hence, this study was conducted on manure samples from Hybrid Converter turkeys raised to 16 weeks of age. The birds were housed in four pens (with an area of 4 m2 each) on litter (straw pellets), at 16 turkeys per pen. Turkeys were divided into four groups: control (C) group; group M – administered monensin (M) with feed; group ME – administered M with feed and enrofloxacin (E) with drinking water; group MED – administered M and E as in group ME and doxycycline (D) with drinking water. Turkeys were raised for 112 days, and then the content of nitrogen, phosphorus, potassium, calcium, and antibiotics was determined in manure samples. The responses of culturable and non-culturable microorganisms, and seven enzymes to the antibiotics contained in manure were tested. One kilogram of manure (fresh weight) contained 4.49-5.27 mg of M, 5.11-7.83 mg of E, and 3.39 mg of D. Antibiotics exerted a highly negative effect on culturable microorganisms. In group MED, the counts of organotrophic bacteria decreased by 40%, Actinobacteria counts decreased by 89%, and fungal counts decreased by 85%. Antibiotics also modified the structure of microbial communities in turkey manure. Bacteria of the phylum Firmicutes and fungi of the phylum Mucoromycota were most susceptible to the analyzed antimicrobials. Antibiotics modified the number of amplicon sequence variants (ASVs) of bacterial families and genera and the number of operational taxonomic units (OTUs) of fungi. The examined antimicrobials decreased the diversity of non-culturable bacteria, but did not induce major changes in fungal diversity. Antibiotics clearly inhibited the activity of enzymes, in particular dehydrogenases and urease. Dehydrogenases activity was reduced by 47%, and urease activity by 72%.