Absorption and Secretion of Some Organic and Inorganic Constituents and the Distribution of These Constituents throughout the Alimentary Tract of Young Calves

Abstract

Distributions of digestal components in successive portions of the gastrointestinal (GI) tract and influx and efflux for several components were measured by a marker ratio technique for calves fed low or high fiber diets in 2 trials. Calves consumed significantly less feed containing 6.5 or 5.4% fiber than that of a feed containing 26.6 or 16.0%. When 13-weeks-old, calves fed at the higher levels of fiber had more dry digesta than those fed at the lower levels. Averages of 405 and 1140 mmoles of volatile fatty acids (VFA) were observed in the entire tract of calves in trial 1 and 618 and 676 in trial 2 for low and high fiber diets, respectively. The rumen contained 55 to 88% of the total VFA and the large intestine plus cecum 11 to 36%. Only 7 to 14 mmoles of lactic acid were observed in each calf, of which 52 to 79% was noted in the small intestine. Significantly more dry and organic matter and less fiber were absorbed from the rumen of calves fed low fiber rations than those fed high fiber rations (P < 0.01). Dry matter and organic matter were secreted into the omasum, abomasum and upper section of the small intestine and absorbed in the remainder of the tract. The omasum absorbed 32 to 45% of each VFA present in the rumen. Further absorption of VFA occurred in the abomasum. The cecum and large intestine produced significant amounts of VFA, part of which was absorbed in the rectum. Lactic acid was produced in the abomasum and small intestine and absorbed in all other sections. Efflux of phosphorus, calcium and ash exceeded influx in the rumen and lower GI tract but was variable in omasum and abomasum and reversed in the upper section of the small intestine. Sodium absorption occurred in the rumen, lower section of the small intestine and rectum, whereas secretion occurred in the abomasum, upper section of the small intestine, large intestine and cecum. Water was absorbed in the omasum, lower small intestine, large intestine, cecum and rectum and secreted into the abomasum and upper section of the small intestine.