Effect of physical activity of laying hens on bone condition

The experiment was performed to study the combination of effects of fatty acids profiles of diets and physical activity (training) on several bone characteristics. Three experimental diets with different fat sources were fed to 12 laying hens each: Palm oil (PO), Soybean oil (SO), and Linseed oil (LO). The fat sources corresponded to a low content of poly unsaturated fatty acids (PUPA) - PO, a high content of omega-6 (n-6) fatty acids - SO, and a high content of n-3 fatty acids (LO). Half of the hens of each dietary treatment (6 x 3 = 18 birds) were exposed to exercise by walking on a running treadmill (EG) through the four wks lasting experiment, whereas, the remaining 18 hens served as a control group (CG) and were permanently kept in the individual cages with limited walking space. At the end of the experiment different bone characteristics were determined at the tibia by computer tomography, shear force tool and chemical analyses. The application of training affected some bone characteristics. The same was true for the dietary fat source. But, the overall effect of diets on bone characteristics was not significant. Nevertheless, there was a trend of higher level of total area and corticalis area in LO group as compared to the PO and SO groups. Physical exercise did not significantly affect bone characteristics. But there was a trend of higher level of total area and corticalis area in the LO group as compared with PO and SO group. Total density and cortical density showed the opposite tendency. Significant diet x exercise interactions were observed for total area (TOT_A), corticalis area (CORT_A) and corticalis density (CORT_DEN). In tendency, diet PO resulted in lower TOT_A, CORT_A and SSI, but in higher TOT_DEN and SSI. Running on the treadmill resulted in lower TOT_A and CRT_A for diets LO and PO, whereas, higher values were observed for birds with exercise fed on diet SO. The relation was opposite for corticalis density. Here, lower values were observed for birds without exercise fed on diets LO and PO. CORT_DEN was lower for birds with exercise fed on diet SO. It is concluded that in hens fed on diets low in n-3 fatty acids physical exercise can improve bones condition.