48 Disrupting hindgut microbiota through the diet alters strongyles infections in horses

Abstract

Although little is known in horses, interactions between gut microbiota and intestinal parasites have been suggested in other species. Understanding how diet may affect these relationships could be a lead in the search for alternative anthelmintic solutions. In horses, the forage/cereal ratio can substantially influence the composition and functions of the hindgut microbiota. Additionally, polyphenols could carry natural anthelmintic activity. This study aimed at evaluating the effect of high-fiber or high-starch diets on the intestinal microbiota and strongyle infection in horses, and the impact of supplementation with sainfoin, a polyphenol-rich plant. Twelve naturally infected adult geldings (7 ± 2 years old,515 ± 53 kg BW) were enrolled in a 4 periods × 4 treatments Latin square design. Groups were formed based on fecal egg count (FEC) before the trial, age, and bodyweight. Experimental periods lasted 21 d (D0 to D21) and were separated by 21 d wash-out periods. The 4 iso-energy, iso-protein treatments consisted in high-fiber (HF; 18.5g DM hay/kg BW) or high-starch diets (HS; 8.0g DM hay+6.3g DM barley/kg BW; 1.9g starch/kg BW/meal), to which were added either control pellets (CONT; 3.1g DM sunflower meal+hay/kg BW) or sainfoin pellets (SF; 3.1g DM Equifolia [Multifolia]/kg BW). Feces were collected on D0, D7, D14, and D21 to assess strongyles excretion through FEC, and on D21 to investigatebacterial diversity and composition using both culture and sequencing technics. Mixed effect models were used to evaluate the effect of the day, the diet and supplementation on these parameters. A day*diet*supplementation interaction was found for FEC (P < 0.001): FEC did not differ between groups at D0, but horses fed the treatment HS CONT had higher FEC than the others at D21 (P < 0.01). Horses fed diet HS had a lower bacterial diversity (Shannon index; P = 0.03), higher relative abundances of Proteobacteria and Succinivibrionaceae (P < 0.01), and lower relative abundance of Lachnospiraceae (P < 0.001) than the horses fed diet HF. The Bacteroidota and Prevotellaceae were more abundant in horses supplemented with sainfoin (P < 0.01). Horses fed diet HS had a lower concentration of cellulolytic bacteria and higher concentrations of amylolytic and lactate-using bacteria (P < 0.001) than horses fed diet HF. These results show that diet and addition of sainfoin can impact both the hindgut microbiota and the intestinal parasitism in horses, which suggests existing relationships between them. Further microbiome analyses may provide data on the effects of specific bacterial taxa or microbial functions on intestinal parasitism.