View More View Less
  • 1 Texas A&M University Department of Poultry Science College Station TX 77843-2472 USA
  • | 2 Texas A&M University Center for Chemical Characterization and Analysis, Department of Chemistry College Station TX 77843-3144 USA
  • | 3 Texas A&M University Department of Animal Science College Station TX 77843-2471 USA
  • | 4 Agricultural Research Services Southern Plains Research Center, U.S. Department of Agriculture 2881 F&B Road College Station TX 77845 USA
  • | 5 University of California at Los Angeles Department of Cardiology, Geffen School of Medicine Los Angeles CA 90025 USA
  • | 6 University of Arkansas Food Science Department Fayetteville AR 72704 USA
Restricted access


A method has been developed for the study of passage rates and mean residence times (MRT) of test rations through the gastrointestinal tracts of layer hens. The use of rare earth elements as stable indigestible markers monitored by neutron activation analysis has been previously demonstrated in numerous species. In this study hafnium was used to mark corn and alfalfa rations as well as a combination ration made up of 90% alfalfa and 10% corn. The primary goal of the study was to evaluate the potential for use of rare earth stable markers in poultry digestion and to determine efficiency of meal marking, optimum exposure rates and determination limits for use in the design of future experimental protocols. Three groups of 10 hens each were fed a particular marked meal with fecal droppings monitored for 24 hours. The hens were sacrificed after a second dosed feeding and a delay of two or seven hours, and digesta was collected from each portion of the gastrointestinal tract. Fecal dry matter as well as digesta collected was then prepared for analysis and the elemental concentrations of hafnium were measured with instrumental neutron activation analysis (INAA). Element adsorption on alfalfa was far less efficient than on the corn ration, limiting the applicability of much of the alfalfa data to digestion studies. Passage rate curves were prepared for corn. The marker was found to primarily concentrate in the ileum at both sacrifice times.