[Resistance to colonization of the gastrointestinal tract]

The microflora naturally present in the intestinal tract of mammals and birds will ensure that pathogenic bacteria will not become colonized or will have difficulty in doing so and cannot grow into large populations in the intestinal tract. This phenomenon is termed 'colonization resistance'. The microflora of the animals is transmitted from parents to offspring and is species-specific. When contacts between parent animals and young animals are broken off, the young are colonized by an adventitiously present microflora which possesses only part of the favourable characteristics. A high pressure of infection by pathogenic bacteria, poor general resistance, the use of antibiotics, fasting, variations in the diet and stress also are factors which usually have an adverse effect on the microflora present in the host. In addition, age is a factor. Young animals relatively often show disturbances of the intestinal flora. The animals are particularly susceptible to intestinal disease immediately after weaning. Methods are suggested, by which disturbances of the intestinal flora due to the above may be prevented.