Effect of dehydrated alfalfa on equine gastric and faecal microbial ecosystems

Abstract

Disturbances of the gastric and hindgut ecosystems can lead to damage of the mucosa in the stomach and to intestinal colic. Some studies suggested that alfalfa could have preventive and healing capacities against gastric ulcerations. Preliminary data suggest that buffering capacity of alfalfa could also be beneficial for the hindgut ecosystem. The objective of this study was thus to assess the effect of dehydrated alfalfa pellets on the bacterial composition and the microbial activity of the equine gastric and faecal ecosystems. Six adult horses allotted in three pairs were studied in a 3 diets x 3 periods Latin square design experiment. During the 18-days experimental period, horses were fed grass hay (57% of total DMI) plus rolled barley and high-protein pellets (27% and 16% of total DMI) that represented a total intake of 1.8% BW / day. High-protein pellets consisted of alfalfa (obtained from 2 different processes, ALF – 2.35mcal/kg DM, 16.9% DM CP, 27.2% DM NFC, 10.8% DM ash, 2.1% DM Ca) and sunflower meal (SFM – 2.26 mcal/kg DM, 29.1% DM CP, 13.8% DM NFC, 7.2% DM ash, 0.5% DM Ca) pellets. Daily starch intake (289g) was divided into 2 equal meals. During the 5-day wash-out period, horses were fed grass hay and rolled barley (93% and 7% of total DMI respectively). On day 18 of the experimental period, faeces and gastric content were collected 3:00 and 3:30h respectively after morning barley + high-protein pellets meal to assess microbial ecosystem parameters. Horses fed ALF had significantly lower gastric concentrations of amylolytic bacteria than the ones fed SFM (P=0.04). On the contrary, amylolytic bacterial concentrations were higher in the faeces of horses fed ALF (P=0.01) compared to SFM diets, as well as lactate-utilizing and pectinolytic bacterial concentrations (P=0.05 and P=0.04 respectively). However, no significant modification of the pH, VFAs proportions, VFAs and lactic-acid concentrations were measured in gastric content and faeces. Regarding gastric health, minimizing carbohydrate fermentation could be beneficial, although VFAs concentrations were not different in this study between ALF and SFM diets. In the hindgut, higher lactate-utilizing concentrations could be advantageous to limit hindgut acidosis. Further work is required to understand the mechanisms that altered gastric and faecal bacterial ecosystems in horses fed the alfalfa diet and to investigate whether other proportions or processed forms of alfalfa in the diet would be more beneficial.