Hemicellulose does not affect iron bioavailability in chicks

Two iron repletion experiments using hemoglobin as a response criterion were conducted to assess effects of hemicelluloses on iron bioavailability to chicks. In Experiment 1, iron bioavailability from intact fiber sources was determined by adding tomato pomace (14.6% hemicelluloses), soybean hulls (20.6% hemicelluloses), beet pulp (21.5% hemicelluloses), orchard grass (24.1% hemicelluloses) and corn fiber (55.2% hemicelluloses) to a casein dextrose basal diet providing 0.4-4.1% hemicelluloses to the diet. Test foods were analyzed for iron, total dietary fiber, neutral detergent residue, neutral detergent fiber, acid detergent fiber, acid detergent lignin, pectins and uronic acids. Hemicelluloses were determined by the difference of neutral detergent residue minus acid detergent fiber. Iron bioavailability was determined by the standard curve method to be (percent relative to ferrous sulfate using hemoglobin as the response criterion) as follows: tomato pomace, 82.0; soybean hulls, 94.0; beet pulp, 26.5; orchard grass, 68.9; corn fiber, 69.4. Iron bioavailability was not related to hemicellulose content of test foods or diets. In Experiment 2, the effect of psyllium husk (a fiber source that contains predominantly hemicelluloses) on iron bioavailability from ferrous sulfate was assessed. Bioavailability was determined by the slope ratio method where treatments consisted of graded levels of ferrous sulfate in the presence and absence of 5% dietary psyllium. Although iron intrinsic to psyllium was unavailable, bioavailability of ferrous sulfate iron was not affected (P > 0.05) by the presence of psyllium. Thus, there was no clear effect of hemicelluloses on iron bioavailability. However, some feeds that contained high levels of hemicelluloses had low intrinsic iron bioavailabilities, suggesting that other dietary factors are primarily responsible for determining iron bioavailability from these feed components.