Gastrointestinal Sites of Absorption and Endogenous Secretion of Calcium and Phosphorus in Dairy Calves.

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Abstract
Eight Holstein male calves, 12 to 15 weeks of age were given Ce144 twice daily in their feed for 7 days at which time equilibrium was reached in fecal concentration. The animals were slaughtered and ingest a samples were taken from 12 sites throughout the gastrointestinal tract. The ratio of Ce144 to Ca or P was calculated to determine net absorption or net endogenous secretion of these elements at various sites. Secretion of P into the rumen and omasum and absorption of Ca and P from the abomasum are indicated. The sites of Ca absorption are not always associated with P secretion. Appreciable secretions of Ca and P in the lower tract are not present or they are balanced by an equal absorption.