Effect of ellagic acid on body weight, nutrient digestibility, fecal microbiota, and urolithin A metabolism in Thoroughbred horses

Abstract This study aimed to investigate the effects of ellagic acid (EA) supplementation on body weight (BW), nutrient digestibility, fecal microbiota, blood biochemical indices, and urolithin A metabolism in 1-yr-old Thoroughbred horses. A group of 18 1-yr-old Thoroughbred horses, with an average weight of 339.00 ± 30.11 kg, were randomly allocated into three groups of six horses each (three males and three females). The control group (n = 6) received only the basal diet, whereas test groups I (n = 6) and II (n = 6) were fed the basal diet supplemented with 15 mg/kg BW/d and 30 mg/kg BW/d of EA, respectively, for 40-d. The results showed that test group I and II horses had a significant increase in total weight gain by 49.47% and 62.74%, respectively, compared to the control group. The digestibility of various components in the diets of the test group horses was improved, including dry matter, organic matter, gross energy, neutral detergent fiber, acid detergent fiber, and calcium. Additionally, the digestibility of crude protein and phosphorus (P) in test group II horses increased significantly by 10.96% and 33.56% (P < 0.05), respectively. Moreover, EA supplementation significantly increased the fecal abundance of Firmicutes, Bacteroidetes (P < 0.05), Fibrobacterota, p-251-o5, Desemzia incerta (P < 0.05), and Fibrobacter sp. (P < 0.05), while reducing the abundance of Proteobacteria, Pseudomonadaceae, Pseudomonas, and Cupriavidus pauculus (P < 0.05 or P < 0.01). Fecal samples from test group II showed 89.47%, 100%, and 86.15% increases in the concentrations of acetic acid, valeric acid, and total volatile fatty acids, respectively. In addition, the plasma levels of total protein, and globulin increased significantly in test groups I (7.88% and 11.35%, respectively) and II (13.44% and 16.07%, respectively) compared to those in the control group (P < 0.05). The concentration of urolithin A in fecal and urine samples was positively correlated with increasing doses of EA. These findings suggest that supplemental feeding of EA improved nutrient digestibility, blood biochemical indices, and fecal microbiota in 1-yr-old Thoroughbred horses, promoting growth and development.