Comparison of the pharmacological properties of the gut of the young animal with those of the adult

Abstract

The transition from foetal to nee-natal existence involves an abrupt change in intestinal function. The relatively passive role of the foetal gut must rapidly become that of a completely adequate absorbing membrane (Moog, 1962) able to cope with all nutritive requirements, and even, in some species, with absorption of intact colostral antibodies.

Nevertheless, the nee-natal intestine has properties by no means identical with those of the adult, since post-natal development occurs both in morphology and function (Spencer, 1964). This seems particularly true of herbivores.

Various aspects of the digestive system of the calf have been investigated: digestive enzymes were studied by Huber et al (1958) by killing calves at various ages and examining the enzymes present in the gut. This showed that pancreatic lipase, protease and amylase increased during the first post-natal week, intestinal lactase decreased with age, and maltase remained static. The dimensions of the various stomach compartments were studied by Godfrey (1961) who found that the reticulo-rumen was still developing at seventeen weeks, while the abomasum had stopped developing at five weeks. Small intestine transit times were examined by Smith (1964) who found no consistent changes between one and twenty weeks of age, while Deutsch and Smith (1957) showed that antibody absorption had largely ceased by twenty-four hours after birth. . Despite the work of the above authors and others, much of the field remains unexplored. It was decided therefore to examine the changes in motor activity of the intestine, and its responses to drugs, in vitro and in viva (Section I) and also to examine an aspect of the developing mucosa, namely alkaline phosphatase activity (Section II).