Abstract

Common poultry feed ingredients such as soybean meal and its subsequent isoflavones and metabolites (daidzein & genistein) have been found to have positive effects on bone health in estrogen deficient animals; however, the exact role these compounds play has not been well established. A field study was conducted to determine the effects of varying levels of dietary soy (high, standard or no soy) on bone characteristics in Free-range (FR) and Battery caged (BC) laying hens. At the end of an 8-week feeding trial, hens were euthanized and both femurs were removed to determine physical (weight, width, length, volume, density and breaking strength) and chemical characteristics (bone mineral content or BMC). Bird weight and feed consumption was similar in hens living in the FR system and BC system with the exception of hens in the BC system fed a soy-free diet. These hen weights were significantly lower than all other feed treatments in both housing systems, consistent with feed consumption data. Under the conditions of the present study, dietary soy supplementation in FR hens resulted in higher levels of phosphorus, calcium, and magnesium levels in femurs as compared to BC hens on a high soy diet. Within the BC production system, hens receiving soy supplementation had longer femurs that were similar in length to femurs in FR hens. Within the constraints of this study, bones in young laying hens showed minimal signs of fragility, some evidence of demineralization, and the ability to be altered with the combination of exercise and dietary soy supplementation.

Keywords: Laying hen production; Free-range chickens; Bone strength; Bone composition