Effect of Omega-3 fatty acids and physical exercise on egg quality, bone characteristics and physiological parameters in laying hens

It is well proven that eggs enriched with omega-3 fatty (n-3) acids have additional health benefits in humans. Various feeding stuffs may be used for enriching eggs with n-3 PUFA. Besides nutrition physical exercise may play a role in this context. Physical exercise influences both the metabolism of fatty acids and the mechanisms of bone formation. Bone breakage is a serious welfare problem of laying hens. Broken bones were found in about 30% of hens before slaughter and the proportion reached 90% at the end of the processing line. Beneficial effects of n-3 fatty acids have been reported on bone strength in Japanese quail and growing chickens. Thus, the objectives of the present study were to elucidate the relationships between sources of dietary fatty acids and physical exercise in laying hens on performance, egg quality, bone characteristics and some physiological criteria of lipid metabolism. In total 36 brown laying hens were used and 12 hens each were fed with three experimental diets differing only in the fat source: Palm oil (PO), Soybean oil (SO), Linseed oil (LO), corresponding to a low content of poly unsaturated fatty acids (PUFA) ? PO, high content of omega-6 (n-6) fatty acids ? SO, and high content of n-3 fatty acids ? LO. Half of hens of each dietary group (6 birds) were exposed to exercise by walking on a treadmill (EG), whereas, the remaining 6 hens served as a control (CG). EG birds were exposed to a running treadmill every day for the whole experimental period (4 wk). On the first day the birds walked 5 min with the speed of 0.5 miles/h. Then duration of walking and speed was increased progressively until day eleven. Thereafter, until the end of the experiment hens walked 25 min/day. On the first day the distance walked was 67 m and increased to 469 m/day on day eleven. The experimental design was: 3 diets x 2 activities x 6 birds = 36 hens. At the end of the experiment eggs were collected to determine yolk fatty acids profiles and hens were slaughtered to collect blood indicators for lipid metabolism, tibia bones to determine bone characteristics and hearts and livers to calculate relative weights. Diets significantly influenced egg weight, yolk proportion and fatty acids profiles. The highest egg weight was observed for SO and the highest yolk proportion for LO. Contents of SAT and MUFA were significantly higher in eggs of group PO, whereas, LO and SO showed a higher content of PUFA. Eggs of treatments SO and LO had the highest proportions of linoleic acid and linolenic acid, respectively. N-6 and n-3 contents in PO and in SO eggs were eight times higher than for LO (P