Mineral composition and rates of flow of effluent from the distal ileum of liquid-fed calves.

1. Liquid-fed calves (aged 1(1/2)-4 months) examined more than five weeks after inserting a re-entrant fistula into the distal ileum, of normal sodium and potassium status and without abnormal gut infection, showed mean emergence rates from the ileum for sodium, potassium and water of 2.3 m-mole/hr, 0.38 m-mole/hr and 21 g/hr respectively after 16 hr fasting.2. Sodium and potassium emergence rates changed little when the residues from a milk or glucose-solution feed arrived at the distal ileum. When magnesium chloride was added to a glucose-solution feed an increase sometimes occurred but only in association with decreased small-intestine transit time.3. Widely differing sodium and potassium intakes had no appreciable direct effect on their emergence rates. Continued feeding of a diet deficient in either ion, however, altered the calf's metabolism and led to appropriate changes in the sodium/potassium ratio of ileal effluent. These changes were not simulated by injecting adrenal cortex hormones. The ratio also decreased when ileal effluent was allowed to discharge for several weeks without being returned to the colon. It was abnormally high in samples obtained less than five weeks after inserting cannulae.4. An increase in sodium and potassium emergence rates, which often occurred spontaneously at about 3 months of age, appeared to be due to infection and was usually prevented by giving aureomycin orally.5. Water emergence rate reflected changes in the emergence rates of osmotically effective constituents and isotonicity was maintained. In effluent after fasting, the cations involved were mainly sodium and potassium, and [Na] + [K] was approximately constant (mean 132 m-mole/l.). In effluent following feeds of milk or glucose, magnesium chloride solution, [Na] + [K] was depressed and [Na] + [K] + 1.5 [Mg] was approximately constant (mean 139 m-mole/l.). Magnesium behaved as it were mainly ionic. Calcium had no apparent osmotic effect and was probably insoluble.6. Bicarbonate was the major anion in ileal effluent after a milk feed with smaller amounts of chloride, phosphate and some other unknown anion(s).