This study was conducted to evaluate the effects of various fat sources on productive performance, blood biochemical variables and immune responses of laying hens. Laying hens were divided into seven groups, which received i) basal or control diet (no oil); ii) and iii) basal diets containing 1% and 3% soybean (SB) oil; iv) and v) basal diets containing 1% and 3% kilka oil (KO), and vi) and vii) basal diets containing 1% and 3% soybean fatty acids (SFA). Productive performance was evaluated from day 1 to day 84. Blood biochemical variables and immune responses were assessed on days 28, 56 and 84 of the trial. The study results indicated that the dietary inclusion of 1% and 3% KO and SFA and 3% SB oil could decrease the feed conversion ratio (FCR) and increase egg production and egg mass in comparison with the control group throughout the study. Immune responses of sheep red blood cells and antibody titre against hemagglutination inhibition (HI) were significantly higher in laying hens fed KO and SFA and 3% SB oil compared with the control group. The serum concentrations of low density lipoprotein-C (LDL-C), very low density lipoprotein-C (VLDL-C) and malondialdehyde (MDA) were not influenced by the inclusion of oil sources. The serum concentration of cholesterol was increased significantly in laying hens that were treated with oil on day 28. The inclusion of fat sources significantly increased the serum concentration of HDL-C. The use of KO and SFA could be recommended at lower levels to improve the performance, immunity and some blood variables in laying hens.
"Experientia docet" - Experience is the best teacher