Horse owners are often interested in feeding supplements to their horses with the intent of improving intestinal health. In some instances, commercial companies have accommodated this desire by producing intestinal feed supplements that are fed along with concentrate feed with the objective of decreasing lactic acid in the hindgut. A crossover design study of nine horses compared fecal pH and digestibility when using two different digestive aid supplements or no supplement at all [Johnson, A.C.B. and Rossow, H.A. Effects of two equine digestive aid supplements on hind gut health. American Society of Animal Science, 2018].
The horses were fed orchard grass hay and sweet cob grain twice daily. Forage increases saliva production, which is helpful in buffering the gastrointestinal tract. Each feeding trial lasted 17 days, and each horse received all three “treatments.” Both digestive aid supplements contained Lactobacillus while one of them (Smartpak - SP) also contained mannanooligosaccharides (MOS) and fructooligosaccharides (FOS), and the other (Platinum Performance - PP) contained the yeast Saccharomyces boulardii.
Hindgut acidosis correlates with fecal pH. The highest fecal pH occurred with the SP treatment; the lowest fecal pH was present when horses were not fed a supplement. In those not receiving a supplemental digestive aid, older horses had a lower pH than younger horses. When PP treatment was offered, the opposite occurred—i.e., fecal pH increased with age. The PP product also contains yeast that should reduce lactic acid bacteria within the cecum and colon. However, fecal pH was not reduced enough with PP to affect hindgut health.
Both supplements decreased digestibility, but PP had the greatest reduction in digestibility. This is of concern since horses rely on “fermentation of feedstuffs to produce volatile fatty acids (VFA) that contribute up to 80% of energy requirements.”
The study results concluded:
- SP increased fecal pH and did not affect digestibility
- PP resulted in decreased digestibility but little effect on fecal pH, which tended toward acidic.
- MOS and FOS in SP improved hindgut health.
- Yeast should improve hindgut health, but this was not observed with PP in this study.
One important point made in the report is that digestive aids are nutraceuticals with minimal quality control by the FDA. In addition, many commercial digestive aid products do not actually contain the concentration of ingredients listed on the label, possibly due to poor processing techniques or poor survival following processing. In general, it is important to recognize that without more quality control of products available for purchase, label claims are not necessarily reliable.