Abstract
The aim of the current study was to assess the impact of raspberry (RA), black currant (BC), and black chokeberry (CA) dried pomace, at 30 g per kg of feed, on performance, egg quality, white blood cells, heterophil:lymphocyte ratio, and lymphatic organs in Hy-Line laying hens. Hens fed a basal diet comprised the control group (CO). A total of 480, 42-week-old Hy-Line commercial hybrid laying hens were randomly divided into 4 equal groups differing in the diet: in control group (CO), the birds received a standard diet, in groups CH, BC and RA, the birds were fed with a standard diet enriched with 30 g/kg of dried fruit pomace: Black chokeberry, black currant, and raspberry, respectively. Differences in yolk color were observed between the CO and groups BC and RA, as well as between groups CA and BC (P < 0.001). The eggs of group RA were characterized by a lower weight (P = 0.001 and P = 0.002) and shell density (P = 0.025 and P = 0.002) in comparison to eggs from the control group CO. The lightest yolk color was observed in the eggs of group BC in comparison with the other groups (P = 0.006). The greatest yolk weight was observed for group CH, while the smallest was for group CO (P = 0.017). Laying hens in the groups BC and RA were characterized at wk 62 of age by a higher percentage of spleen in comparison with the control group CO (P = 0.018). In conclusion, the BC and RA diet resulted in a paler yolk color and was associated with slightly poorer shell quality parameters. On the other hand, the CH and BC diet had a positive impact on the immune system of the laying hens, as confirmed by the changes in the white blood cell smear and the higher spleen percentage. Therefore, the use of these by-products in the diets of poultry, i.e., dried pomace of black chokeberry and black currant may have a positive impact by improving the immunological status of laying hens.