The aim of the study was to evaluate the impact of probiotics obtained from agro-industrial substrates fermented with lactic acid bacteria and/or yeasts on the health and changes in the microbiota of the digestive tract of guinea pigs. Eighty male guinea pigs, Kuri breed, 30 days old and 250 g live weight, were randomly selected and divided into four groups of 20 animals each. T0, Control, T1, Lactobacillus acidophilus and L. bulgaricus. T2, Saccharomyces cerevisiae and Kluyveromyces fragilis and T3. L acidophilus, L bulgariccus, S cerevisiae and K. fragilis. T1, T2 and T3 contained molasses-vinasse substrate in their base, the dose administered was 0.75 mL/animal orally. The parameters evaluated were weight gain, occurrence of diarrhea and mortality, blood profile, macroscopic lesions in the digestive tract organs and changes in the microbiota of the stomach, caecum, small and large intestine. Treatments T1, T2 and T3 improved weight gain (p<0.05) and reduced the presence of guinea pigs with diarrhea (p<0.05) and there was no mortality; hematic indices did not vary significantly (p>0.05) between treatments; animals in the control group presented a greater amount (p<0.05) of macroscopic lesions in the digestive tract organs; in the T1, T2 and T3 group there was an improvement in the natural microbiota. It is concluded that the inclusion of microbial additive in young guinea pigs improves intestinal health, consequently, improves weight gain, reduces diarrhea and deaths, and normalizes the natural microbiota of the gastrointestinal tract.