Chapter 2 Metabolism and population dynamics of the intestinal microflora in the growing pig

This chapter discusses the available information on population dynamics of the intestinal flora in growing pigs and addresses the factors involved in changes of this flora during different stages of the animal's life and in health and disease. The intestinal flora of pigs contains several hundred microbial species, mostly strict anaerobes. A great amount of these bacteria reside in the large intestine that in adult pigs consists of mainly Gram-positive bacteria such as cocci, lactobacilli, eubacteria, and clostridia. The composition of the intestinal microflora is a result of the interaction between the microorganisms that colonize the gut and the intestinal physiology of the pigs. While a part of this microflora is constantly present in the gut (resident flora), some microorganisms have a short residence and dynamically change the composition of the microflora. The stability and diversity of this flora has a tremendous role in maintaining the health status of the pigs, especially during the suckling and post-weaning period. The digestive tract of the newborn piglet is specialized on a diet comprising milk. Therefore, a high lactase activity is present in the small intestine, at least for as long as milk comprises the dominant feed source. While several methods, including molecular-based techniques, are available to detect and identify unculturable bacterial flora of the gut, there is a need for more advanced techniques to measure the functional status of the normal flora in response to dietary feed and environmental stress.