title: Separation of digesta fractions complicates estimation of ileal digestibility using marker methods with Cr2O3 and cobalt-ethylenediamine tetraacetic acid in broiler chickens.
abstract: Marker methodologies to measure ileal and total tract digestibilities of diets varying in content and degradability of dietary fiber in broiler chickens were evaluated. Chromium sesquioxide (Cr2O3) and cobalt-ethylenediamine tetraacetic acid (Co-EDTA) were used as markers of solid and soluble fractions, respectively, and compared with digestibility values obtained with the total collection method. Groups of broilers (n = 17, 11 broilers/group) were assigned to a low-fiber diet or 1 of 2 high-fiber diets, the latter 2 containing 35% rapeseed meal (RSM). Pectolytic enzymes were added to one RSM diet to improve degradability of the fiber fraction. Excreta were quantitatively collected for 96 h, and contents from ileum and ceca were collected at slaughter at 29, 30, or 31 d of age. Chromium recovery in excreta ranged between 86 and 95%, whereas cobalt recovery was considerably lower (66 to 70%). Chromium:cobalt ratio was higher in ileal digesta than in feed. Hardly any chromium was found in the ceca, indicating that separation of the marker and specific digesta fractions occurs. Estimates of apparent total tract digestibility (ATTD) were lower when calculated using the marker method compared with the total collection method, particularly in high-fiber diets. Using Cr2O3 as a marker, differences were relatively small and effects due to enzyme addition were generally similar. Using Co-EDTA as a marker, ATTD of all components were lower compared with values obtained using the collection method (3 to 45 percentage units, P < 0.001), likely related to the low Co recovery. When estimating apparent ileal digestibility (AID), separation of marker and digesta resulted in unrealistically high estimates for the digestibility of nonglucose polysaccharides (54 to 66%), exceeding ATTD values by 16 to 42 percentage units. Moreover, the effect of pectolytic enzyme addition on the AID of nonglucose polysaccharides was in the opposite direction when compared with total collection. The data illustrate that fractionation of digesta, particularly in high-fiber diets, complicates accurate AID measurements in broilers, regardless of the choice of markers used.
authors.affiliation: Animal Nutrition Group, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands Sonja.de.vries@nutreco.com.
authors.forename: S
authors.initials: S
authors.lastname: de Vries
authors.affiliation: Animal Nutrition Group, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors.forename: R P
authors.initials: RP
authors.lastname: Kwakkel
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, PO Box 8129, 6703 HD Wageningen, the Netherlands.
authors.forename: A M
authors.initials: AM
authors.lastname: Pustjens
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, PO Box 8129, 6703 HD Wageningen, the Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: Kabel
authors.affiliation: Animal Nutrition Group, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors.forename: W H
authors.initials: WH
authors.lastname: Hendriks
authors.affiliation: Animal Nutrition Group, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors.forename: W J J
authors.initials: WJ
authors.lastname: Gerrits
mesh_terms: D000821:Animal Feed / Q000032:analysis; D053180:Animal Nutrition Sciences / Q000379:methods*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002645:Chickens / Q000502:physiology*; D017608:Chromium Compounds / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D004043:Dietary Fiber / Q000032:analysis; D004063:Digestion; D004492:Edetic Acid / Q000378:metabolism*; D005260:Female; D041981:Gastrointestinal Tract / Q000502:physiology*; D007082:Ileum / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D017608:Chromium Compounds; D004043:Dietary Fiber; C028222:cobalt-ethylenediamine tetraacetic acid chelate; D004492:Edetic Acid; C023600:chromic oxide
keywords: apparent digestibility; chromic oxide; cobalt-ethylenediamine tetraacetic acid; marker; nonstarch polysaccharide