Effects of dietary water-soluble extract of rosemary supplementation on growth performance and intestinal health of broilers infected with Eimeria tenella.

ABSTRACT

This study was conducted to explore the effect of dietary supplementation of water-soluble extract of rosemary (WER) on growth performance and intestinal health of broilers infected with Eimeria tenella (E. tenella), and evaluate the anticoccidial activity of WER. 360 1-d-old Chinese indigenous male yellow-feathered broiler chickens were randomly allocated to six groups blank control (BC) group and infected control (IC) group received a basal diet; positive control (PC) group, received a basal diet supplemented with 200 mg/kg diclazuril; WER100, WER200, and WER300 groups received a basal diet containing 100, 200, and 300 mg/kg WER, respectively. On day 21, all birds in the infected groups (IC, PC, WER100, WER200, and WER300) were orally gavaged with 1 mL phosphate-buffered saline (PBS) of 8 × 104 sporulated oocysts of E. tenella, and birds in the BC group were administrated an aliquot of PBS dilution. The results showed that dietary supplementation of 200 mg/kg WER increased the average daily gain of broilers compared to the IC group from days 22 to 29 (P < 0.001). The anticoccidial index values of 100, 200, and 300 mg/kg WER were 137.49, 157.41, and 144.22, respectively, which indicated that WER exhibited moderate anticoccidial activity. Compared to the IC group, the groups supplemented with WER (100, 200, and 300 mg/kg) significantly lowered fecal oocyst output (P < 0.001) and cecal coccidia oocysts, alleviated intestinal damage and maintained the integrity of intestinal epithelium. Dietary supplementation with WER significantly improved antioxidant capacity, elevated the levels of secretory immunoglobulin A, and diminished inflammation within the cecum, particularly at a dosage of 200 mg/kg. The results of this study indicated that dietary supplementation with 200 mg/kg WER could improve broiler growth performance and alleviate intestinal damage caused by coccidiosis.

Avian coccidiosis, a prevalent parasitic disease caused by Eimeria protozoa, leads to significant economic losses in the global poultry industry. Currently, the control of coccidiosis in chickens primarily relies on chemical and ionophore anticoccidials. However, the long-term use of these compounds has resulted in the development of drug-resistant strains, presenting a critical challenge. Additionally, the toxic and side effects of ionophore anticoccidials have become increasingly apparent. Thus, there is an urgent need to find economical and environmentally friendly measures to control coccidiosis in chickens. In this study, we established a model of Eimeria tenella infection in broilers to explore whether the water-soluble extract of rosemary (WER) could serve as an alternative method for controlling avian coccidiosis. Our results showed that dietary supplementation with WER (100, 200, and 300 mg/kg) had a beneficial anticoccidial effect, alleviating intestinal damage caused by coccidiosis by enhancing the intestinal antioxidant defense and activating the immune function of the infected broilers. Specifically, dietary supplementation with 200 mg/kg WER emerged as a promising strategy for controlling avian coccidiosis in the poultry industry.