Evaluation of in-feed supplementation of formic acid and thymol as non-antibiotic growth promoters and assessing their effect on antimicrobial resistant E.coli isolated in Turkey

With the rampant usage of antibiotics as growth promoters (AGPs) in poultry sector, there has been alarming concerns of antimicrobial resistant microbes such as Escherichia coli. Diversification of poultry farming due to consumer demand for safer products with higher protein content, turkey production is gaining popularity. Feed additives such as formic acid (FA) and thymol (TH) are effectively replacing AGPs due to their antimicrobial action. This directed the researchers to find alternatives to antibiotics such as thymol and formic acid because of their strong antimicrobial, anti-oxidative, digestive-stimulating properties. To assess the efficacy of FA and TH as growth promoters and their effect on the antimicrobial resistance (AMR) load, the current study (0–12 weeks) was conducted in CARI VIRAT turkey poults (n = 256; unsexed) those were randomly distributed into eight treatment groups: control(T1), AGP (T2), graded levels of FA (T3 to T5) @ 2.5, 5 and 7.5 ml/kg and TH (T6 to T8) @ 120, 240 and 350 mg/kg. Cloacal swab samples were collected at 0, 4th, 8th and 12th week interval and processed further for isolation, identification and assessment of resistance profile of E. coli. The final body weight, cumulative gain and FCR were significantly (p < 0.05) better for birds under supplementation. The Total plate count (TPC) and coliforms showcased a significant (p < 0.001) reduction in the FA and TH supplement groups as compared to control and AGP group. The resistance profile indicated E. coli isolates from AGP group with significantly (p < 0.001) highest resistivity against antibiotics (viz. chloramphenicol, tetracycline, nalidixic acid, chlortetracycline) while isolates from FA (T5) and TH (T8) groups were the least resistant. blaAmpC gene was significantly (p < 0.001) harbored in T2 isolates whereas least detected in T5 and T8. It was inferred that formic acid (7.5 ml/kg) and thymol (360 mg/kg) can effectively replace AGPs and lower AMR burden in poultry.