Nutritional Regulation of Gastric Secretion, Digestion and Emptying

Calcium solubilization and retention in the gastrointestinal tract in chicks (Gallus domesticus) as a function of gastric acid secretion inhibition and of calcium carbonate particle size

In chicks, immature pullets and laying hens, the inhibition of gastric acid secretion by omeprazole, an H+,K(+)-transporting ATPase (EC 3.6.1.36) inhibitor, greatly increased proventricular and gizzard pH values. Consequently, gizzard soluble Ca concentration deceased and the insoluble Ca fraction increased. Inhibition of acid secretion increased duodenal pH values in immature pullets and laying hens but not in chicks. Duodenal soluble and ionic Ca concentrations were lowered by gastric acid inhibition in chicks and to a larger extent in immature pullets and laying hens. The use of Ca of coarse particle size increased the gizzard insoluble Ca fraction in chicks and pullets. However, it did not influence its soluble Ca fraction in chicks but tended to reinforce the negative effect of omeprazole on soluble Ca in the gizzard and duodenum of chicks and laying hens. Coarse particles of Ca led to an increase in gizzard and duodenal soluble Ca at the end of eggshell calcification in laying hens. An enhancement in the level of Ca in the diet from 10 to 36 g/kg increased gizzard soluble Ca and duodenal soluble and ionic Ca concentrations in immature and adult hens. Intestinal Ca retention and bone mineralization was unaffected by gastric acid inhibition in chicks but were largely diminished by the use of coarse particles of Ca. Gastric acid inhibition was associated in laying hens with decreased Ca retention to a small extent and with reduced eggshell quality. These observations confirm that gastric acid secretion is of importance for CaCO3 solubilization but question its role as a prerequisite for intestinal Ca retention in chicks and even in hens fed on a high Ca diet.

Effects of reducing the starch content in oat-based diets with cellulose on jejunal flow and absorption of glucose over an isolated loop of jejunum in pigs

Four pigs fitted with two sets of re-entrant cannulas in the upper jejunum were used to study the effect of two oat-flour (F)- and oat-bran (B)-based diets without or with (FC and BC respectively) addition of 148 g wood cellulose/kg on jejunal flow and absorption of glucose over an isolated loop of jejunum. Mean transit time (MTT) of flow from the proximal re-entrant cannula increased from approximately 1.5 h with diet F to 2 h when feeding diet BC. Both the replacement of oat flour by oat bran and the supplementation of the diets with cellulose led to a significantly longer MTT for dry matter and the carbohydrates, except that cellulose did not have a significant effect on the mTT for the total non-starch polysaccharides. Only the addition of cellulose significantly delayed gastric emptying of the added liquid-phase (Polyethylene glycol 4000) and solid-phase (Cr2O3) markers, whereas no effect of the oat source used was seen. Feeding diets with a higher level of dietary fibre (DF) and lower content of starch, obtained by substitution with cellulose or by feeding oat bran instead of oat flour, reduced the recovery of starch from an isolated loop of jejunum. Consequently, the quantitative absorption of starch was not significantly different between diets when starch was related to the recovery of external markers. However, when related to the recovery of arabinoxylan (AX) there was a significantly lower absorption of starch from the bran-based diets in comparison with the flour-based diets. The capacity to digest and absorb the large quantities of starch entering the duodenum after a carbohydrate-rich meal appears to be the limiting factor for absorption in the upper jejunum. Therefore, any effect of DF on the rate of absorption of glucose is presumably an effect on gastric emptying rather than displacement of the site of starch absorption in the small intestine.

Gastric acid secretion in the chicken: effect of histamine H2 antagonists and H+/K(+)-ATPase inhibitors on gastro-intestinal pH and of sexual maturity calcium carbonate level and particle size on proventricular H+/K+ ATPase activity

1. Cimetidine was more potent 4 hr after a single injection of 25 or 100 mg/kg body wt in increasing gastric pH than other H2 receptor antagonists, ranitidine and famotidine but was less efficient than H+/K(+)-ATPase inhibitors. Omeprazole rose proventricular and gizzard pH at a lower dose than SCH 28080 and Ro 18-5364 (30, 50 and 200 mg/kg body wt, respectively). 2. Proventricular and gizzard pH values were maximal 1 and 4 hr after a single injection of 7.5 mumol/kg body wt omeprazole. Inhibition of acid secretion was maintained for 24 hr after an injection of 100 mumol/kg. 3. H+/K(+)-ATPase activity in vitro was 10 mumol Pi/hr/mg protein in the microsomal fractions of the proventriculus. It was doubled by nigericine and inhibited by SCH 28080. However, western blots by high specific H+/K(+)-ATPase monoclonal antibody 95-A3 and 95-111 recognized a 42 kDa band but hardly exhibited the specific 95 kDa band recognition. 4. Chickens and immature pullets showed a higher H+/K(+)-ATPase activity than laying hens. Calcium level of the diet did not affect the enzyme activity but coarse particles of calcium fed to pullets or laying hens enhanced the H+/K(+)-ATPase activity when compared with ground particles.