Hydroxamic Acid Isolated from Maize Roots Exhibits Potent Antimicrobial Activity Against Pathogenic Escherichia coli in Broiler Chickens

Restrictions on adding antibiotics to animal diets have posed challenges in managing gut pathogens, emphasizing the significance of effective non-antibiotic growth promoters to maintain animal health and productivity. This study assessed the efficacy of hydroxamic acid (HA), derived from local maize varieties, as a non-antibiotic growth promoter in broilers. Among 10 different maize varieties, the Azam variety yielded the highest HA concentration (35 ± 7 μg/g of roots), as quantified by high-performance liquid chromatography (HPLC). In vitro antimicrobial assays demonstrated the lowest minimum inhibitory concentration (MIC) of 0.022 mg for Azam-derived HA against pathogenic E. coli. To further assess in vivo efficacy, 108 birds were allocated at random to six treatment groups. The treatments include birds fed a basal diet without an E. coli challenge (negative control); an antibiotic-treated group challenged with E. coli and treated with enrofloxacin at a dosage of 5 milligrams (mg) per kilogram (kg), administered orally once daily from day 5 post-infection (dpi) for 7 consecutive days (standard); broilers challenged with E. coli and supplemented with a basal diet with HA at concentrations of 1, 10, or 100 mg/kg of feed from 5 dpi for one week (HA 1 mg, HA 10 mg, and HA 100 mg, respectively); and broilers challenged with E. coli without enrofloxacin/HA (positive control). The results demonstrated that birds fed a diet supplemented with the HA-100 mg improved the body weight (BW) and feed conversion ratio (FCR) compared to the positive control group. There were no significant differences (p > 0.05) observed for BW and FCR observed for the broilers fed on the standard and HA 100 mg groups. The addition of HA at 100 mg improved (p < 0.05) the hemoglobin (Hb) and packed cell volume (PCV) and reduced (p < 0.05) levels of malondialdehyde (MDA) compared to positive control group. A significantly low carcass weight (p < 0.05) was shown for positive control birds compared to other groups. Our findings indicate that maize-derived HA presents a phytogenic alternative to antibiotics by controlling enteric pathogens and improving health and performance affected by E. coli infection in broilers.