Ultrastructure of small‐intestinal epithelium in weaned and unweaned pigs and pigs with post‐weaning diarrhoea

Abstract

PLATES CXXV-CXXIX WEANING in the young pig is often followed by a gastro-enteritis, which in turn is frequently associated with the isolation from the faeces of large numbers of organisms of certain serotypes of Escherichia coli. Kenworthy and Allen (1966) showed that in pigs that appeared clinically normal a malabsorption syndrome could occur, and suggested that E. coli was not the primary agent in post-weaning diarrhoea, even though the organism might be present in large numbers.Because enteritis associated with E. coli affects such a wide variety of animal species and its aetiology is not understood, we decided to study the malabsorption syndrome further. We examined the morphology, microflora and in-vitro absorptive efficiency of the small intestines of unweaned and weaned healthy pigs, and of weaned pigs with diarrhoea. The morphological studies included histological and histochemical studies with the light microscope, and examination of the ultrastructure of epithelial cells with the electron microscope. The electron-microscope studies, together with relevant data on the E. coli population in the intestine, form the subject matter of this paper.The strains of E. coli isolated from our animals are divided into two groups on the basis of haemolysin production. This is because most strains isolated from outbreaks of bowel oedema or gastro-enteritis in pigs produce haemolysins (Sojka, Lloyd and Sweeney, 1960). Haemolytic E. coli bacilli are commonly present in the faeces of apparently normal, healthy pigs, occasionally in large numbers Smith, 1963), but in the disease syndromes it is the profuseness and purity of growth on primary isolation that have attracted attention. MATERIALS AND METHODSThe pigs were 23 Large Whites from a closed herd. They sucked their dam until 3 wk old, when half of the litter was weaned. No bedding was available during the suckling period, and the pen was so arranged that the piglets did not have access to the sow's food. At weaning, half of the weaned pigs were bedded on sawdust litter, the other half being left without bedding of any kind. They were treated in this way since young pigs are prone to eat their bedding and this could be a complicating factor in the interpretation of results.

Observations on the structure of the small intestine on foetal, neo-natal and sucklings pigs

“…First, a well-developed apical system is present for a considerable period after the normal time of closure, and secondly, some endocytosed material is retained within the cells as inclusion bodies, even though absorption in the pig is effectively non-selective. There is also evidence that the apical system may persist for a far longer period than that covered in our investigation: Kenworthy et (1967) have reported STRUCTURE OF SMALL INTESTINE OF PERINATAL PIG 527 a well-developed apical system in the jejunum of suckling piglets after 6 days and have found that traces of it are still present after 5 weeks. For these reasons, it is suggested that endocytosis is not a limiting factor, and that closure represents a failure either of intracellular processing or of release.…”

“…All the studies on the fine structure of the intestine of the neo-natal pig which are known to the authors have concerned pieces of jejunum (Kenworthy, Stubbs & Syme 1967;Matisson & Karlsson 1965Sibalin & Bjorkman 1966;Vodovar & Flechon 1966;Staley, Jones & Marshall 1968), although observations in this laboratory have suggested that vacuolation in neo-natal, unsuckled piglets is best developed in the terminal third of the small intestine. There are no ultrastructural studies of foetal piglets known to the authors and little attention seems to have been paid to the structural changes which occur after the initial suckling period.…”

Increasing viscosity of the intestinal contents alters small intestinal structure and intestinal growth, and stimulates proliferation of enterotoxigenicEscherichia coliin newly-weaned pigs

“…The pigs fed rice 1 high-viscosity CMC had the worst diarrhoea and the highest levels of haemolytic E. coli shed in their faeces. The small intestinal villi of these pigs also were atrophied, a common feature seen in PWC (Kenworthy et al 1967). It is unknown whether the shorter villi in this group were a result of, or a precipitating factor for, the development of intestinal disease.…”

Effect of Dietary Soybean Meal on the Microscopic Anatomy of the Small Intestine in the Early-Weaned Pig

“…Accepted December 8, 1988 disaccharidase concentrations and reduced absorption. Damage of the intestinal epithelium can be caused by rotavirus and E. coli pathogens (Leece et al, 1982), but several workers (Kenworthy et al, 1967;Miller et al, 1984a,b;Hampson, 1986b) have shown that decreased villus height and increased lamina propria depth are not dependent solely on the presence of pathogenic organisms in the intestine. Miller et al (1984a,b) suggested that a transient hypersensitivity response to dietary antigens may be the predisposing factor causing these changes.…”