Doxycycline Attenuates Pig Intestinal Microbial Interactions and Changes Microbial Metabolic Pathways

SIMPLE SUMMARY: The stability and balance of the intestinal bacterial community is the foundation of animal health. It is unclear how the therapeutic dose of doxycycline affects pig intestinal bacterial ecology. In our study, the effect of high doxycycline concentration on the bacterial community was not reflected in the diversity of the microbial community structure but in the bacterial interaction. Moreover, the functional prediction also showed that bacterial interaction may be related to changes in metabolic pathways. This study provides a reference for the effect of therapeutic doxycycline on the pig intestinal bacterial community in pig breeding. ABSTRACT: Doxycycline is a therapeutic veterinary antibiotic commonly used in pig breeding. In this study, 27 fattening pigs of 33.5 ± 0.72 kg were divided equally into 3 groups. Doxycycline at 0, 3, and 5 mg/kg body weight was added to the feed in groups CK, L and H. The medication and withdrawal periods were set at 5 and 28 days. The results showed that the doxycycline average concentrations in groups L and H during the medication period were 117.63 ± 13.54 and 202.03 ± 24.91 mg/kg dry matter, respectively. Doxycycline levels were lower than the detection limit after 20 days. Doxycycline did not affect the diversity of the intestinal microbial community structure. The relative abundances of Streptococcus were significantly higher in treatment groups than that in group CK, and Alishewanella, Vagococcus, Cloacibacterium, and Campylobacter abundances were significantly positively correlated with doxycycline concentration. Interestingly, the microbiota cooccurrence network suggested that high doxycycline concentration weakened the interactions among bacteria until day 33. Functional prediction showed that doxycycline significantly altered metabolic pathways related to the cell membrane. The results revealed that the use of doxycycline during pig breeding can affect bacterial abundance during the withdrawal period, and it may affect interactions among bacteria and change the intestinal metabolic pathways.