A three-week course of probiotics given to foals proved ineffective in reducing the chances of the animals developing diarrhea, researchers have found.
Up to 60 percent of foals develop diarrhea within six months of birth.
Effective preventive measures are limited, but scientists acknowledge there is potential for probiotics to have a role.
Canadian, Danish and Swiss researchers conducted their study to determine whether a probiotic affected the incidence of foal diarrhea. They conducted a randomized placebo-controlled field trial involving 72 healthy foals in southern Ontario, Canada.
Foals were administered either a placebo or the probiotic once daily for three weeks. They were monitored throughout, as well as for an additional week.
A total of three fecal samples were taken from each foal at biweekly intervals.
They found that the overall incidence of diarrhea was 59 percent, involving 41 of the 72 foals. The incidence did not differ between treatment groups, but foals treated with probiotics were more likely to develop diarrhea requiring veterinary intervention.
Age had a significant effect on the incidence of diarrhea, with foals aged 8–15 days having the highest risk.
The duration of diarrhea and soft feces were not significantly different between groups, they reported in their findings, published in the peer-reviewed Journal of Veterinary Internal Medicine.
Angelika Schoster and her colleagues reported that the prevalence of Clostridial perfringens shedding was 55 percent, with no difference between treatment groups. The prevalence of Clostridial difficile shedding was 11 percent.
“There was no benefit of administering a three-week course of probiotics,” they reported, “but potential adverse effects were noted.”
They continued: “Whether the probiotics lacked a clinical effect, or the choice of strains or dose was inadequate, is unknown.”
Clostridial shedding was not influenced by the probiotic use, they said.
The probiotic formulation used comprised four Lactobacillus species and Bifidobacterium animalis lactis, which have been shown to inhibit the growth of C. difficile and C. perfringens in a laboratory setting. This, they said, made them worthy of evaluation as an animal probiotic.
The lack of effect of the probiotic formulation on C. difficile and C. perfringens shedding in the study was disappointing, they said, given its inhibitory activity against these pathogens noted in the laboratory.
The researchers commented: “Probiotics are often approached by owners and veterinarians with the thought that they will at worst be ineffective, something that might not be true.
“Results of this study do not indicate that the concept of probiotic treatment is futile in prevention of neonatal diarrhea. Yet, these results, combined with those of another study that identified a negative impact of probiotics in neonatal foals, raise concerns.
“Selected probiotics have been shown to be effective for some gastrointestinal disorders in humans and domestic animals yet prevention of neonatal diarrhea has not been reported.”
Recent advances in the knowledge of equine gut bacteria could be used to design equine-specific probiotics, they said. Further investigation in this area is required.
“This study, though, suggests that commercial products that lack published safety and efficacy data should be approached with caution.
“Commercial probiotic products often contain unreliable and varying amounts of active ingredients and scientific evidence supporting these formulations is lacking.”
They noted also that probiotics had been shown to be unable to colonize the gastrointestinal tract of horses. “It is therefore unlikely that they can act beyond their period of administration.
The researchers were based across three institutions – the University of Guelph in Canada; the University of Zurich in Switzerland; and the University of Copenhagen in Denmark.
Schoster, A., Staempfli, H.R., Abrahams, M., Jalali, M., Weese, J.S. and Guardabassi, L. (2015), Effect of a Probiotic on Prevention of Diarrhea and Clostridium difficile and Clostridium perfringens Shedding in Foals. Journal of Veterinary Internal Medicine. doi: 10.1111/jvim.12584
The full study can be read here.