Fatty acids profile and oxidative stability of eggs from laying hens fed diets containing hemp seed or hempseed cake
High levels of polyunsaturated fatty acids (PUFAs) are desirable in eggs for its nutritional quality, but render them vulnerable to oxidation. The aim of this trial was to assess the effects of dietary intake of hemp (seeds or cake) on the fatty acid (FA) profile and oxidative stability of eggs. The control diet (C), which was composed of corn, soybean meal and sunflower oil (2.5%), was compared with two experimental diets that were designed to replace sunflower oil with fat from hemp seed (HS diet) or hempseed cake (HC diet). One hundred and twenty Tetra-SL LL laying hens (24-week old) were used in a 10-week trial. Each treatment was replicated five times with eight birds each. Average hen-day egg production was not affected by feeding either the HS or the HC diet. The α-linolenic acid (ALA) concentration in eggs was increased by substituting the HS- or HC-based diets fed to the hens with dietary ALA. Similar deposition profiles were exhibited by eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA) in yolks in response to increasing the dietary ALA supply. The HS group showed a greater concentration of egg yolk ALA and EPA than the HC group, which had a higher concentration of linoleic acid (LA). These alterations in yolk composition resulted in n−6 : n−3 FA ratio values as low as 2.98 and 4.15 for HS and HC, respectively, compared to 11.07 for the control diet. The atherogenicity index and cholesterol level were not affected by hemp (seed or cake) inclusion, while the thrombogenicity index decreased when compared to the control diet. On days 0, 15 and 30 of storage (4 °C), two eggs were selected randomly from each replicate (totalling 10 eggs per treatment) and analyzed. The PUFAs were not affected by storage. An exception occurred in the HC group, in which eggs had lower n-6 FA content. Egg storage for 30 d led to a reduction in egg α-tocopherol and an increase of malondialdehyde (MDA) concentration, an indicator of lipid peroxidation. The HS treatment resulted in the lowest MDA (0.22 mg MDA/kg yolk for fresh eggs and 0.35 mg for eggs in 30-day storage). The study demonstrates that the level and type of PUFAs, level of α-tocopherol and duration of egg storage significantly affected the oxidative stability of eggs. The results obtained suggest that the inclusion of hemp seed appears to be more effective in maintaining the oxidative stability of egg lipids than hempseed cake.
Keywords: egg enrichment, α-tocopherol, malondialdehyde, omega-3, storage time