The effect of different oil supplementations on laying performance and fatty acid composition of egg yolk

The aim of the research was to determine effects of different combinations of rapeseed and fish oil - instead of soybean oil - on the performance of laying hens and on the profile of fatty acids in egg yolks, especially on n-3 polyunsaturated fatty acid (PUFA), when such oils are added to the diet of laying hens. The research was carried out on 90 laying hens of the Hy-Line hybrid ranging in age from 32 to 36 weeks old. Hens were divided into three groups (30 laying hens per groups) and fed with a commercial mixture that contained 17% of crude protein and 11.6 MJ ME. The research lasted for 28 days. The control group (C) was given diets with soybean oil supplemented in the amount of 5%, and experimental groups (E1 and E2) were fed diets that contained a combination of fish and rapeseed oils in different amounts. Diets given to the E1 group contained 3.5% of fish oil and 1.5% of rapeseed oil, while the E2 group was fed diets with 1.5% of fish oil and 3.5% of rapeseed oil. Production characteristics of hens were monitored during the whole experiment. Portion of saturated (SFA) and unsaturated fatty acids (MUFA and PUFA), as well as &alpha;-linolenic (&alpha;LNA, C:18:3n-3) eicosapentaenoic (EPA, C20:5n-3) and docosahexaenoic (DHA, C22:6n-3) acid were shown as a percentage of total fatty acids contained in yolk. There were statistically significant differences (P<0.05) only in the hens&rsquo; end weights and laying intensity between the C and E1 group, as well as between the C and E2 group. The portion of SFA in total fatty acids contained in yolk was not statistically significant (P>0.05) among investigated groups. Higher content of MUFA was noticed in both experimental groups, if compared to the control (E1 41.37%: E2 40.72%, C 36.95%, P<0.05). Content of &alpha;LNA differed significantly (P<0.001) between E1 and the control group, and the content of DHA differed significantly (P<0.001) between E1 and the control group, as well as between E2 and the control group. Total n-3 PUFA was increased in the E1 group for 2.10, and in the E2 group for 1.41 times than in the control group. The ratio of n-6/n-3 PUFA was the lowest (P<0.05) in egg yolks of the E1 group (4.01), followed by that of the E2 group (6.56), and finally that of the control group (11.08).