Horse Probiotics are necessary for a healthy digestive system so your horse can absorb all the nutrients you are paying to feed him or her. Information on affordable probiotics for horses will ensure that you are able to find the best probiotic for your horse. Probiotics help horses absorb nutrients, and regulate healthy sugar balance in their body, so that probiotics help both overweight or under weight horses— and help keep horses at a good weight and health. Probiotics are the friendly bacteria that keep the gut running smoothly.