Development of intestinal disaccharidase activities in nursing calves.

1. The disaccharidase activities of mucosal homogenates from the small intestine, caecum and colon of cattle were observed. 2. In nursing calves, lactase, cellobiase and trehalase activities were located mainly in the upper part of the small intestine, whereas maltase and isomaltase activities were more uniformly distributed along the small intestine and were also found in the caecum and colon. Intestinal cellobiase, trehalase, maltase and isomaltase activities were very low compared with lactase activity and intestinal sucrase activity was not detected. 3. Intestinal lactase, cellobiase and trehalase activities were the highest at birth and decreased rapidly with age. These activities increased during the late fetal period. On the other hand, intestinal maltase and isomaltase activities showed no increase during the late fetal period and nursing period of 6 months, 4. Relatively low pH values of intestinal contents of 5.5-6.0, which were close to optimum pH of intestinal disaccharidases, were observed in the upper part of the small intestine. 5. In adult cattle, intestinal lactase and cellobiase activities were found but only with negligible levels. Intestinal trehalase activity was also found with low level. Intestinal maltase and isomaltase activities were found to be similar levels to those found in calves. Intestinal sucrase activity was not detected. 6. Based on the results of disaccharidase activities and tissue weights, overall utilizable quantities of lactose and maltose by small intestinal mucosa in nursing calves were estimated, Jap. J. Zootech. Sci., 51(1):58-68,1980 It has been known that intestinal lactase activity of calves is high in the early weeks of life but decreases with age1-3). And it has been also shown that intestinal maltase activity is very low and shows no increase with age, and intestinal sucrase activity is absent1,2,4). From these observations, it is seemed that young calves are able to utilize lactose but possess poor ability to utilize maltose and starch, and are unable to utilize sucrose. However these activities reported are expressed either as units per mg protein of mucosa or as units per g dry tissue, and therefore do not necessarily imply the digestive capacity of these carbohydrates by intestinal mucosa. The capacity seems to also depend largely on increase of tissue weight and on change of distribution of activity along the small intestine, and may be influenced by change of luminal pH. However little detailed observation including these factors has been reported of development of disaccharidase activities in calves. In the present study, we investigated the sequential development of mucosal disaccharidase activities and of patterns of their distributions in the small intestine , caecum and colon of nursing calves with intestinal tissue weights and content pH's, Jap. J. Zootech. Sci., 51(1):58-68 58 1980 Intestinal Disaccharidase of Nursing Calf and estimated the overall utilizable quantities of lactose and maltose by small intestinal mucosa. Materials and Methods Thirteen calves and three fetuses of Japanese Black Cattle were used . The calves were kept with their dams and nursed voluntarily . They were given concentrates and hay ad libitum from 1-4 weeks of age . And two or three calves were killed at 4,610,12 and 26 weeks of age by bleeding out from the carotid artery after local infusion of procaine hydrochloride solution . Two newborn calves were also killed within 24 hours after birth. Of these calves , one nursed about a day, but the other removed from its dam immediately after birth . The fetuses were removed from their dams which were normally fed and killed by electrical stunning and bleeding at 5.5 and 7 months after conception. The mean body weights of experimental animals at slaughter are shown in Table 1. Two adult cows and two fattenning steers were included in this study as the reference of adult levels of disaccharidase activities . The cows, weighed 332kg, were fed only rice straw for three months before slaughter and the steers, weighed 531kg, were fed concentrates ad libitum . They were killed by electrical stunning and bleeding. Immediately after slaughter, the small and large intestines were removed as soon as possible and weighed with their contents . In calves, samples of intestines for enzyme assay and of contents were taken from seven sites along the small intestine at 2.2±0.7,14.0±3.7,31.7±7.6,47.9±8.9,64.2±7,0,79 .3±7.1 and 95.3±2.7% (mean±S.E.) of the full length of the small intestine measured from the pylorus. These sites were decided arbitrarily and were referred to as duodenum, proximal jejunum, middle jejunum, distal jejunum, proximal ileum, middle ileum and distalileum, respectively. Samples were also taken from the caecum and sigmoid colon. In fetuses, samples for enzyme assay were taken from four sites along the small intestine arbitrarily and from the caecum. These sites along the small intestine were at 1 .9±0.6, 21.1±5.5,63.0±7.5 and 85.1±4.5% (mean±S.E.) of the full length of the small intestine from the pylorus and were referred to as duodenum, proximal jejuno-ileum, middle jejuno-ileum and distal jejuno-ileum, respectively. Weights of the empty intestines were measured. Weights of the reticulo-rumen and abomasum with and without their contents were also measured. The intestine samples were chilled with ice and transported to the laboratory. The intestinal contents from calves were preserved with a saturated solution of HgCl2. And then the pH of these contents were measured by Beckman Zeromatic pH Meter (Beckman-Toshiba Ltd, Tokyo, Japan). Each intestine sample was cut open, washed in ice-cold solution of 0.15M-NaCl and gently blotted with a piece of filter paper. The mucosa was scraped off with a glass slide and weighed. A known quantity of the mucosa was homogenized with a given quantity of ice-cold 0.15M-NaCl solution in Universal Homogenizer (Nihon Seiki Ltd, Tokyo, Japan) at top speed for 3 minutes. Then the homogenate was centrifuged at 3000rpm for 10 minutes in order to remove nuclei and larger cell debris, and the supernatant was