TY - JOUR
T1 - Technical note
T2 - an algebraic method for calculating fecal output from a pulse dose of an external marker.
AU - Galyean, M. L.
PY - 1993/12
Y1 - 1993/12
N2 - Fecal output estimates derived from a one-compartment, Gamma-2, age-dependent model were compared with estimates derived algebraically by computing the area under the marker excretion curve for lambs given a pulse dose of ytterbium-labeled forage. Lambs were fed one of four diets (as-fed basis): 100% alfalfa hay, 100% prairie hay, 50:50 alfalfa:sorghum grain, and 50:50 prairie hay:sorghum grain. For the one-compartment model, fecal output was calculated as the dose of Yb (micrograms) divided by the initial concentration in the compartment (micrograms of Yb/gram of DM) multiplied by the age-dependent rate constant (hours-1). For the algebraic method, fecal output was calculated as the dose of Yb divided by the area under the marker excretion curve ([micrograms of Yb/gram of fecal DM].hours), both with the full complement of fecal samples and with fecal samples collected at 12-h intervals. Fecal output estimated by the three methods did not differ (P > .15) from measured fecal output (total collection). Marker retention time calculated from the one-compartment, age-dependent model was numerically greater (P > .10) than retention time calculated algebraically (sum of concentration x time divided by sum of concentrations weighted for collection interval) for lambs fed all four diets. These results suggest that the area under the marker excretion curve generated from a pulse dose of Yb-labeled forage will provide estimates of fecal output that do not differ from those calculated from a one-compartment, age-dependent model.
AB - Fecal output estimates derived from a one-compartment, Gamma-2, age-dependent model were compared with estimates derived algebraically by computing the area under the marker excretion curve for lambs given a pulse dose of ytterbium-labeled forage. Lambs were fed one of four diets (as-fed basis): 100% alfalfa hay, 100% prairie hay, 50:50 alfalfa:sorghum grain, and 50:50 prairie hay:sorghum grain. For the one-compartment model, fecal output was calculated as the dose of Yb (micrograms) divided by the initial concentration in the compartment (micrograms of Yb/gram of DM) multiplied by the age-dependent rate constant (hours-1). For the algebraic method, fecal output was calculated as the dose of Yb divided by the area under the marker excretion curve ([micrograms of Yb/gram of fecal DM].hours), both with the full complement of fecal samples and with fecal samples collected at 12-h intervals. Fecal output estimated by the three methods did not differ (P > .15) from measured fecal output (total collection). Marker retention time calculated from the one-compartment, age-dependent model was numerically greater (P > .10) than retention time calculated algebraically (sum of concentration x time divided by sum of concentrations weighted for collection interval) for lambs fed all four diets. These results suggest that the area under the marker excretion curve generated from a pulse dose of Yb-labeled forage will provide estimates of fecal output that do not differ from those calculated from a one-compartment, age-dependent model.
UR - http://www.scopus.com/inward/record.url?scp=0027765228&partnerID=8YFLogxK
U2 - 10.2527/1993.71123466x
DO - 10.2527/1993.71123466x
M3 - Article
C2 - 8294301
AN - SCOPUS:0027765228
VL - 71
SP - 3466
EP - 3469
JO - Journal of Animal Science
JF - Journal of Animal Science
SN - 0021-8812
IS - 12
ER -