Effects of soy supplementation on bone characteristics and egg quality in peak production laying hens

In the last few decades equol, a metabolite of the isoflavone daidzein, has become the target of various animal and human studies. Coined the key to health benefits associated with soy foods, equol formation been implicated in the healthy profiles associated with Asian populations. As a metabolite of daidzein, equol must be synthesized from its precursor by intestinal bacteria; however, clinical and epidemiological studies indicate that only about a third of the general human population possess the microflora necessary to metabolize equol. Research indicates that by supplementing laying hens with soybean meal, equol deposition into table eggs can be stimulated, thereby creating a functional direct source of this estrogenic compound, independent of gut microflora. Though equol enhanced eggs may be created through soy supplementation, isoflavones are bioactive and have various physiological effects when consumed. Thus, the purpose of this research project was to examine the impact of various levels of soy supplementation (soy-free-SF, standard soy-SS, soy enhanced-SE) on bone characteristics and egg quality in young battery-cage (BC) and free-range (FR) laying hens. The research was conducted concurrently with a study that determined the level and rate of equol deposition into table eggs from the same flock.;Findings of the current research showed that SE combined with physical activity had a significant impact on bone health as evidenced by increased femoral weight (P=0.005), length (P=0.0066), bone strength (P=0.016) and compression energy (P=0.013). Additionally, higher levels of phosphorous (P=0.012), magnesium (P<0.0001), zinc (P=0.0002) and the calcium/ phosphorous ratio (P=0.001) were observed in femurs originating from FR layers given SE feed. Quality analysis showed that eggs collected from both soy treatments (SS and SE) were larger and heavier (P<0.05) than eggs collected from SF layers. Moreover, eggs collected from SF hens had thinner eggshells (P=0.0435) than those from soy treated (SE and SS) layers. Furthermore, data analysis also showed that soy treatments can negatively affect yolk quality as evidenced by decreased vitelline membrane strength (P=0.034) and less red yolks (P<0.0001) in hens fed SE and SS diets.;Overall, the effects associated with dietary isoflavones via soy supplementation beneficially altered various quality characteristics that affect both animal welfare and poultry farmers. Decreased bone fractures associated with avian osteoporosis could improve animal welfare as well as curb economical losses associated with layer mortality. Furthermore, stronger eggshells could reduce the percentage of cracked and downgraded eggs.