Factors Affecting Manganese Homeostasis in the Chick

124 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.Plant and animal sources of manganese (Mn) are, for the most part, unavailable to the chick. Corn (C), soybean meal (SBM), fish meal (FM) and wheat bran (WB) reduced tissue Mn concentrations when added to a purified phytate- and fiber-free diet. Although these feed ingredients contain significant quantities of Mn, as little as 1.0% WB, 2.5% FM, and 5.0% of a C-SBM mixture markedly depressed Mn deposition in tissues. Moreover, the addition of these feed ingredients to the purified diet, containing the minimal requirement level of Mn (14 mg/kg as MnSO(,4)), depressed chick performance over the course of a 7-week feeding period. FM also increased the severity of perosis.Subsequent research indicated that the fiber fraction of WB and the C-SBM mixture accounted for virtually all of the Mn-binding capabilities of these ingredients. In contrast, the tissue Mn-lowering capacity of FM was shown to result from the ash fraction. Therefore, any beneficial effect from the Mn present in the feed ingredients was more than offset by factors in the ingredients which exerted negative effects on Mn retention.Although it is commonly assumed that Mn competes with iron and cobalt for gut absorptive sites, our work shows minimal interaction between these trace elements. Neither extreme excesses of iron nor cobalt exerted a negative effect on Mn retention. Dietary Mn also had little effect on iron or cobalt utilization, although there was some evidence that excess Mn depressed hemoglobin and hematocrit in Fe-deficient and Fe-marginal chicks.Based upon tibia Mn uptake, the absorption efficiency of Mn was estimated as 2.40% in chicks fed a phytate- and fiber-free diet. Rapid excretion of absorbed Mn occurs in the chick, with a faster turnover rate occurring in bile (t 1/2 = 1.1 days) than in bone or pancreas (t 1/2 = 6-7 days). It appears that the avian's relatively high dietary requirement for Mn cannot be explained by inefficient gut absorption, but instead by a more rapid turnover of body Mn relative to that which occurs in mammalian species.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD