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

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Abstract
Liquid-fed calves (aged 1 1/2-4 mo.) examined more than 5 weeks after inserting a re-entrant fistula into the distal ileum, of normal Na and K status and without abnormal gut infection, showed mean emergence rates from the ileum for Na, K and water of 2.3 m-mole/hr. 0.38 m-mole/hr. and 21 g/hr. respectively after 16 hr. fasting. Sodium and K emergence rates changed little when the residues from a milk or glucose-solution feed arrived at the distal ileum. When Mg chloride was added to a glucose-solution feed an increase sometimes occurred but only in association with decreased small intestine transit time. Widely differing Na and K intakes had no appreciable direct effect on their emergence rates. Continued feeding of a diet deficient in either Fe, however, altered the calf''s metabolism and led to appropriate changes in the Na/K 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 5 weeks after inserting cannulae. An increase-in Na and K emergence rates, which often occurred spontaneously at about 3 mo. of age, appeared to be due to infection and was usually prevented by giving aureomycin orally. Water emergence rate reflected changes in the emergence rates of osmotically effective constituents and iso-tonicity was maintained. In effluent after fasting, the cations involved were mainly Na and K, and [Na] + [K] was approximately constant (mean 132 mmoleA.). In effluent following feeds of milk or glucose, Mg 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. Bicarbonate was the major anion in ileal effluent after a milk feed with smaller amounts of chloride, phosphate and some other unknown anion(s).