Investigation was made on intestinal bacteria of mother and offspring of six typical domestic animals, to wit: Cow, Horse. Pig, Sheep, Goat, Dog, by using proper methods of bacterial selective media. In other words, the fresh feces of all the above animals was tested for amount and frequency of occurrence of the following five types of bacteria: E. coli types group, Aerobacter type group, all Streptococci group, Enterococci group and also Cl. welchii type group, with the following results: 1. Frequency of appearance of all five types of bacteria is about the same in the feces of all the animals tested. 2. In all cases where the above five types of bacteria were found in the feces of the mother animals who nourished their young, the same bacteria were found in the young. 3. There are differences in amounts of the above bacteria found in same of the parent and offspring animals. So with E. coli group bacteria in found in greater amounts in the females parent than in the offspring of sheep and goats. The Aerobacter group is found in greatest amounts in the parent horse and the young cow. The Enterococci group exists in greatest amounts in young cows. In young horses, Cl. welchii appears in greater amounts as age increases. 4. It was discovered that between the pH of feces and bacteria of intestinal tract are in some way has related each other. The conclusion to be drawn from the tests in that there are little differences in the amount and frequency of the five groups of bacteria to be found in mothers and offsprings of animals in the mammal group.