Citric Acid and Magnolol Ameliorate Clostridium perfringens Challenge in Broiler Chickens

SIMPLE SUMMARY: In this study, the combined inhibitory effect of citric acid (CA) and magnolol (MA) on C. perfringens was first confirmed. Subsequent determination of growth curves and SEM morphological observations showed that the best synergistic effect occurred at a mass ratio of 50:3. The medicine combination not only inhibited the growth of C. perfringens, but also damaged its cell structure at 265 μg/mL. The effect of medicine combination is more significant at 530 μg/mL. This study then used the growth performance, inflammatory levels, antioxidant capability, and changes in intestinal microbiota to comprehensively evaluate the therapeutic effect of CA and MA on C. perfringens challenge in chickens. The results showed that CA and MA can inhibit inflammation via the inhibition of the TLR/MyD88/NF-κB pathway and enhance the antioxidant capability via the enhancement of the Nrf2/HO-1 pathway, thus mitigating the adverse effects of C. perfringens challenge. Furthermore, while the medicine combination had a relatively good effect at a dosage of 0.2%, the most effective dosage for the restoration of intestinal microbiota was 0.1%. These results indicate that the addition of CA and MA to daily feed (0.1–0.2%) for chickens can function as a new protection measure for controlling C. perfringens challenge in chickens. ABSTRACT: Clostridium perfringens (C. perfringens) is a common pathogenic bacterium implicated in the enteric diseases of animals. Each year, the disease is responsible for billions of dollars of losses worldwide. The development of new phytomedicines as alternatives to antibiotics is becoming a new hotspot for treating such diseases. Citric acid (CA) and magnolol (MA) have been shown to have antibacterial, antioxidant, and growth-promoting properties. Here, the bacteriostatic effects of combinations of CA and MA against C. perfringens were investigated, together with their effects on yellow-hair chickens challenged with C. perfringens. It was found that the optimal CA:MA ratio was 50:3, with a dose of 265 μg/mL significantly inhibiting C. perfringens growth, and 530 μg/mL causing significant damage to the bacterial cell morphology. In animal experiments, C. perfringens challenge reduced the growth, damaged the intestinal structure, activated inflammatory signaling, impaired antioxidant capacity, and perturbed the intestinal flora. These effects were alleviated by combined CA–MA treatment. The CA–MA combination was found to inhibit the TLR/Myd88/NF-κB and Nrf-2/HO-1 signaling pathways. In conclusion, the results suggest the potential of combined CA–MA treatment in alleviating C. perfringens challenge by inhibiting the growth of C. perfringens and affecting the TLR/MyD88/NF-κB and Nrf-2/HO-1 signaling pathways.