Showing papers on "Mineral absorption published in 1965"
TL;DR: The apparent absorption of calcium, phosphorus and total dry matter along the gastrointestinal tract of the laying hen, was followed using yttrium-91 as a non-absorbed tracer, which appeared to be greater in the proximal parts of the intestine than in the distal parts.
Abstract: The apparent absorption of calcium, phosphorus and total dry matter along the gastrointestinal tract of the laying hen, was followed using yttrium-91 as a non-absorbed tracer. Percentage calcium and phosphorus absorption appeared to be greater in the proximal parts of the intestine than in the distal parts. This differ ence was smaller for total dry matter. Percentage calcium absorption was not signifi cantly influenced by its dietary level, nor did the latter influence the absorption of dry matter. Percentage absorption of phosphorus was, however, depressed by the higher dietary calcium level. Egg shell deposition was associated with increased calcium and to a smaller degree, phosphorus absorption. It did not influence dry matter ab sorption. A heavy endogenous phosphorus excretion was observed in the duodenum. The identification of the sites of mineral absorption is important for understanding the mechanism involved in the mineral absorption. This problem was studied mainly by in vitro and in situ experimenta tion. The in vitro studies such as those of Schachter and associates (1, 2) provide information on the capacity of various intestinal segments to absorb calcium. However, the rate and percentage of cal cium absorption may also depend on the rate of passage of food, which is quite variable in the various intestinal segments (3, 4). Therefore, in vitro methods can not measure the relative contribution of each segment to total calcium absorption in vivo. A different method for studying calcium absorption is the use of oral doses of 45Caor its injection into different parts of the intestine (5, 6). This method, how ever, measures mainly the outflux of cal cium from the intestine and not the net absorption which is the difference between the outflux and the influx. Chandler and Cragle (7) used I44Ceas a non-absorbed tracer to study calcium and phosphorus absorption in calves. The ratio of calcium and phosphorus to 144Ceat any point in the intestine measures the cumu lative percentage absorption up to this point. Similarly, Bolton (8) used cellulose as a tracer for estimation of protein and available carbohydrate absorption along the tract of chickens. Marcus and Lengemann (3) reported that 81Ywas not ab sorbed in the rat. Preliminary trials in this laboratory showed that this isotope was not absorbed by colostomized chickens. Following an oral dose of 91Ymixed in some feed, 93% of the dose was detected in the feces voided during the first 24-hour period, and 3% in the following 24-hour period. No activity could be detected in the urine of these animals. Therefore, 91Ywas used in the present trial to follow the absorption of calcium and phosphorus along the intestinal tract of laying hens. The possibility that dietary calcium and the presence of a calcifying shell in the uterus may modify the pattern of calcium and phosphorus absorption was also investigated.
122 citations