Studies on calcium and magnesium in the alimentary tract of sheep I. The distribution of calcium and magnesium in the contents taken from various parts of the alimentary tract

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Abstract
1. The distribution of calcium and magnesium in the contents of the reticulo-rumen sac, omasum, abomasum, small intestine, caecum and colon of the sheep was studied by means of ultrafiltration through collodion membranes.2. In all organs except the abomasum considerable proportions of calcium and magnesium existed in a non-ultrafilterable form. In the abomasum where the pH is normally between 2 and 3 there was virtually no bound calcium or magnesium. The proportion of ultrafilterable calcium in the small intestine appeared to be dependent on the pH of the digesta, low pH values favouring higher proportions of ultrafilterable calcium. With magnesium this correlation was less obvious and appeared to be upset by unknown factors in the animals consuming a fresh grass diet.3. From calculations it is postulated that the concentrations of ultrafilterable calcium and magnesium in rumen fluid are insufficient for these elements to be absorbed as freely diffusing ions, whereas in the abomasum and duodenum the concentrations of ultrafilterable calcium and magnesium are in favour of a net uptake from the gut.