LE TRANSIT DIGESTIF CHEZ LE LAPIN. III. — INFLUENCE DE L'HEURE ET DU MODE D'ADMINISTRATION SUR L'EXCRÉTION FÉCALE DU CÉRIUM-I4I, CHEZ LE LAPIN ALIMENTÉ AD LIBITUM

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Abstract
The fecal excretion of cerium-141 was studied in 40 rabbits, 8 wk-old, non constrained and always fed ad libitum. The administration of the marker, either in liquid form or deposited on feed pellets, was made either at 9.30 a.m. or at 4.30 p.m. Feces were collected every hour for 72 h after the administration. The amounts of dry matter and radioactivity excreted were determined in each sample of feces collected. After 72 h, the rabbits were slaughtered and the residual visceral radioactivity as well as its distribution were measured. The results confirm the existence of a rhythm of fecal dry matter excretion with a minimum between 9.00 a.m. and 4.00 p.m. and a maximum between 7.00 p.m. and 1.00 a.m. This rhythm can be compared with that of the voluntary feed intake. The excretion of 141Ce started at a rapid rate (5% eliminated within 4-8 h), reached 66 to 79% within the 1st 24 h, and was not entirely finished 72 h (1.5-2.5% still present in the viscera). The mean retention times in the digestive tract ranged between 14 and 21 h. Intake of the marker in the morning increased the time of retention in the digestive tract by 3-4 h as compared with the time noticed after the afternoon intake. The administration of 141Ce in liquid form led to a lengthening of the retention time by 3-4 h. The results seem to confirm the existence of a physical segregation of the particles in the proximal colon.