26 week old meat-type geese (Kolos) were fed maize or a mixture of 90% maize and 10% linseed for 6 weeks. In a second experiment 9 week old liver-type geese (Grimaud G36) were force fed for 20 days either maize or the same mixture of maize and linseed as described above. Linseed incorporation into maize in meat-type geese significantly decreased final body weight, the relative liver weight and abdominal fat pad content, but failed to change the fat content of liver, breast meat and the relative abdominal fat percentage. Feeding linseed however, increased significantly the total n-3 fatty acid content of liver and breast meat. Force feeding with 10% linseed decreased significantly, by 51% the fatty liver weight and by 50% the fat content of liver. No significant effect of dietary treatment was found in the breast meat fat and abdominal fat contents. Using linseed during force-feeding increased the total n-3 fatty acid, linolenic acid, DPA and DHA contents of liver by 4-8 times and total n-3 fatty acids and linolenic acid content of breast meat by 2 times. According to these results n-3 fatty acids inhibit hepatic lipogenesis dramatically in overfed liver-type geese. The modification of fatty acid profile of goose tissues can be more successful with meat-type birds.

Fat content and fatty acid profile of two pike yearling groups grown on two different diets were compared. The groups originated from culture on artificial feed. One group (cultured pike fed first pellet then prey-fish (PF)) was fed with natural food, live prey-fish, while the other one (cultured pike fed exclusively pellet (PP)) by trout feed through a 3-month experimental period. Growth of pike was lower with PP than with PF. The trout feed resulted in an increase of the fat content of fillet and the formation of abdominal fat depots. Feeding of natural food decreased the fat content. The proportion of the saturated fatty acids in fillet was higher in the (PF) group. The n-6 fatty acids (arachidonic C20:4n-6 and docosatetraenic C22:4n-6 acids) were lowest in PP-fed pike. Regarding total n-3 fatty acids ratio there was no significant difference between the groups, but the level of α-linolenic (C:18:3n-3) acid showed significant difference among groups.

The effect of supplementary methionine and fats of different saturation levels on the glutathione redox system of growing broiler cockerels was studied. The diet of three groups of chicks was supplemented with corn germ oil, beef tallow and fish oil at the levels of 30 g/kg and 50 g/kg of feed, respectively. The diet of further three groups was supplemented with methionine (5 g/kg of feed) in addition to the different fat sources. Control chicks were fed with a compound feed without methionine and fat supplementation. Reduced glutathione (GSH) and glutathione disulphide (GSSG) content as well as glutathione peroxidase activity in the liver were determined and GSH/GSSG ratio was calculated at day old and then at one and three weeks of age. Our results indicate that supplementary methionine stimulates both the synthesis of the glutathione redox system and glutathione peroxidase activity in growing chickens in the first period of postnatal life, when the risk of lipid peroxidation is high due to feeding unsaturated fats in the diet.

The effects of cod liver oil (rich in n-3 fatty acids and vitamin A) and pumpkin seed oil (rich in n-6 fatty acids) with α-tocopheryl acetate supplementation on fatty acid composition, vitamin A and vitamin E concentration and lipid peroxidation of egg yolk were studied. Laying hens (n = 144) were fed on six experimental diets supplemented with 4% fat and dl-α-tocopheryl acetate (0, 30 and 60 mg/kg) for three weeks. Feeding cod liver oil diets resulted in higher (P < 0.05) concentration of n-3 polyunsaturated fatty acids (PUFA) in yolk compared to feeding pumpkin seed oil diets. Vitamin E content of diets did not affect the fatty acid composition of egg yolk. No relationships were observed either between dietary PUFA and deposition of vitamin A and E in the egg. Supplementation of diets with 30 mg/kg α-tocopheryl acetate resulted in higher yolk vitamin E contents regardless of the type of added fat compared to the unsupplemented groups. However, the level of 60 mg/kg added α-tocopheryl acetate was more effective in the cod liver oil than in the pumpkin seed oil group. Concentration of vitamin A in yolk was not affected by different vitamin A contents in the cod liver oil and pumpkin seed oil diets without added tocopherol, whereas the effect of dietary α-tocopheryl acetate on the vitamin A content in yolk was dose-dependent. The rate of lipid peroxidation, measuring thiobarbituric acid reactive substance (TBARS) values in yolk was significantly (P < 0.001) related to the concentration of n-3 fatty acids in yolk lipids, however, no relationship was found between TBARS values and total PUFA content. Oxidative stability of yolk was proportionably enhanced by dietary α-tocopheryl acetate treatments in the cod liver oil group, whereas TBARS values in the pumpkin seed oil group remained constant after α-tocopheryl acetate supplementation. In contrast to vitamin E concentrations, vitamin A values in yolk were not related to TBARS values in either group.

The influence of dietary fat supplementations differing in the ratio of n-6 to n-3 polyunsaturated fatty acids (PUFA) on the effects of glucagon and insulin on plasma glucose, triglyceride (TG), and TG-rich lipoprotein concentrations was investigated in laying hens. Birds were fed either a low-fat control diet (LF) or diets supplemented with 4% pumpkin seed oil (PO; rich in n-6 PUFA) or 4% cod liver oil (CO; rich in n-3 PUFA). After 4 wk feeding of the experimental diets, hens were implanted with wing vein catheters and injected with porcine glucagon (20 microg/kg BW) and porcine insulin (0.5 IU/kg BW), 2 to 5 h after oviposition. Plasma glucose, TG, and TG-rich lipoprotein concentrations were determined from 10 min pre-injection to 60 min post-injection. PO diet resulted in a prolonged plasma glucose response to glucagon administration and altered hypoglycemic response to insulin. However, CO diet did not influence plasma glucose response to either glucagon or insulin administration compared to LF diet. The effects of glucagon and insulin on plasma TG and TG-rich lipoproteins were similar for all diets regardless of the amount or type of fat. The results suggest that feeding dietary fats with high n-6 to n-3 PUFA ratio alters the glucagon and insulin sensitivity of plasma glucose in laying hens. Fats rich in n-3 PUFA seem to have no influence on the plasma glucose response to glucagon and insulin.