They must also be storable until they are fed to the animal. There are several kinds of probiotics currently in use. Lactobacilli are bacteria that produce lactic acid. Generally speaking, these bacteria have been shown to provide an alternative to antibiotic treatments to control infections. Lactobacilli have been particularly beneficial in young animals, where decreased mortality has been noted in animals supplemented with probiotics.
Probiotics can encourage the early establishment of beneficial microbes in the gut.
They are also useful during weaning, a time when animals are most susceptible to illnesses such as diarrhea. Probiotics have also provided benefits to young animals at other times of stress, such as during transportation, tailing, castration, or, in adult animals, at times such as calving or illness. Yeast has been used as a protein source for animals, but it can also be added to the diet as a live culture in small quantities to alter gut functions. Another fungal probiotic, known as Aspergillus oryzae, has shown substantial response from beef cows and calves on poor pastures. Growth rates of 800 grams per day have been achieved with the use of the probiotic, compared to 570 grams per day in untreated animals.