Klaus Krämer

Enrichment of eggs with n−3 polyunsaturated fatty acids: Effects of vitamin E supplementation

Eggs enriched with n−3 polyunsaturated fatty acids (PUFA) could contribute to dietary intake of these healthful fatty acids (FA). Because n−3 PUFA are highly susceptible to peroxidation, a first part of the study with Leghorn laying hens was carried out to investigate the influence of different levels of fish oil (0, 0.7, 1.4, 2.8, or 5.6%, respectively) in the diet on n−3 PUFA, cholesterol, vitamin E, and lipid peroxidation product contents in eggs. Addition of fish oil to a complete diet based on wheat, rye, tapioca, and soybean constituents containing 11 IU vitamin E/kg resulted in increased n−3 PUFA content in egg yolk, mainly due to accumulation of docosahexaenoic acid. Cholesterol was not altered up to 2.8% fish oil in the diet. The vitamin E content of the yolk was insufficient for the protection of PUFA from peroxidation. Addition of up to 2.8% fish oil to laying hen diets increased the n−3 PUFA content of yolks with a concomitant imbalance between vitamin E and PUFA, leading to increased levels of cytotoxic aldehydic lipid peroxidation products such as malondialdehyde (MDA). In a second part of the studies, the balance between vitamin E, PUFA, and lipid peroxidation was analyzed during the period of storage of n−3 PUFA-enriched eggs produced after feeding the laying hens with 1.5% fish oil diets with different concentrations of vitamin E (0, 5, 10, 20, 40, 80, 160 IU/kg). Storage of eggs resulted in a marked loss of vitamin E in yolk. In stored eggs, the cytotoxic lipid peroxidation products MDA, 4-hydroxynonenal, and 4-hydroxyhexenal were reduced in response to vitamin E supplementation. To prevent the increase of cytotoxic aldehydic lipid peroxidation during production and storage of n−3 PUFA-enriched eggs, a high vitamin E supplementation with at least 80 IU vitamin E/kg is needed.

Effects of feeding various tocotrienol sources on plasma lipids and aortic atherosclerotic lesions in cholesterol-fed rabbits

Abstract Tocotrienols exert hypocholesterolaemic and antioxidant effects, and may hence have anti-atherogenic properties. Therefore, the aim of this study was to investigate the cholesterol-lowering and anti-atherogenic effects of tocotrienols in cholesterol-fed rabbits. Rabbits were fed a basal diet (control) supplemented with γ-tocotrienol, γ-tocotrienyl acetate, mixed tocotrienols or α-tocotrienol for 12 weeks. All treatments resulted in significant increases in plasma tocotrienols. None of the treatments, however, had significant effects on serum lipids or size of atherosclerotic lesions. A trend towards a decrease in plasma cholesterol was observed following γ-tocotrienol treatment (−22%) after 6 weeks. The decrease was mainly attributable to a reduction in LDL cholesterol (23%), whereas HDL cholesterol increased (14%). This trend was mirrored in a non-significant reduction in lesion area (20%). Our results demonstrate that tocotrienols are absorbed, but have little effect on plasma lipids and atherosclerosis in cholesterol-fed rabbits.

Bioavailability of water- and lipid-soluble thiamin compounds in broiler chickens.

The bioavailability of thiamin mononitrate, thiamin chloride-hydrochloride and benfotiamin was compared in broiler chickens. A thiamin-deficient diet was supplemented with either 1.8 and 1.5 mg/kg thiamin equivalent as water-soluble salts, or with 1.5 and 1.2 mg/kg thiamin equivalent as benfotiamin, respectively, and fed to 3 replicate groups/treatment for 21 days. Weight gain, feed consumption and feed conversion rate were not significantly affected by solubility or dietary level of thiamin. Likewise, using biochemical indices of thiamin status (erythrocyte transketolase activation coefficient, and thiamin concentrations in blood and liver), no differences were found between the water-soluble thiamin salts, indicating that they have identical potency. In contrast, biochemical indices of thiamin status showed a significantly higher bioavailability for benfotiamin than for the water-soluble sources.