1. Effects of canthaxanthin supplementation of the maternal diet on the antioxidant system of the developing chick were investigated. 2. Three hundred and twenty female broiler breeder birds were housed in one of 4 controlled environment rooms with 3 replicates for all treatments, with the exception of the control treatment of which there were 4 replicates. All birds received one of 5 diets: control low xanthophyll diet, or the same diet supplemented with 3, 6, 12 or 24 mg/kg canthaxanthin in the form of Carophyll Red. At 30 weeks of age 60 eggs from each of the 5 groups were incubated. At d 16 of the embryo development, at d 1 and d 7 posthatch tissue samples were collected and analysed by HPLC-based methods. 3. Canthaxanthin accumulation in the egg yolk was proportional to dietary content. Furthermore, at 12 to 24 mg/kg canthaxanthin was associated with an increase in gamma-tocopherol concentration in the egg yolk. Canthaxanthin was transferred from the egg yolk to the developing embryo and, as a result, its concentration in the liver of the embryo at 16 and in 1-d-old chicks was increased. Even at d 7 posthatch canthaxanthin concentration in the chicken liver was elevated. 4. Canthaxanthin supplementation of the maternal diet at 12 mg/kg was associated with an increased alpha-tocopherol concentration in the liver of 1-d-old chicks and resulted in decreased tissue susceptibility to lipid peroxidation. 5. Canthaxanthin supplementation at 6 to 24 mg/kg was also associated with a delay in alpha-tocopherol depletion from the liver for 7-d posthatch. As a result of the increased canthaxanthin and vitamin E concentrations in the liver of 7-d-old chicks, tissue susceptibility to lipid peroxidation decreased. 6. The results support an idea that dietary carotenoids can modulate antioxidant systems of the developing chicken.

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Selenium is considered to be one of the most controversial trace elements. On the one hand, it is toxic at high doses and there is a great body of information related to environmental issues of Se contamination. On the other hand, Se deficiency is a global problem related to an increased susceptibility to various diseases of animals and humans and decreased productive and reproductive performance of farm animals. Optimisation of Se nutrition of poultry and farm animals will result in increased efficiency of egg, meat and milk production and even more important, will improve quality. From the data presented in the review it is clear that the main lesson which we have to learn from nature is how to use organic selenium in animal and human diets. Selenium-enriched yeast (Sel-Plex) is the result of such a lesson and it is just a matter of time before animal nutrition moves completely from using ineffective sodium selenite to organic selenium. Other lessons from nature will follow. Recent advances in genomics and proteomics, in association with descriptions of new selenoproteins, will be a driving force in reconsidering old approaches related to Se nutrition. Probably 90% of all Se research has been conducted with sodium selenite and we now understand that the natural form of selenium is different. The main advances in Se status assessment and Se requirements were established based on the activity of glutathione peroxidase (GSH-Px), an enzyme which for many years was considered to be the main selenoprotein. Recently it was discovered that it is only one of at least 25 various selenoproteins. Se research and practical applications are developing quickly and they are very exciting and promising.

Significant difference (P < 0.05) between values in the presence and absence of exogenous vitamin E.membrane. This view is supported by reports that the fertilizing ability of chicken semen is improved by dietary supplementation with n-3 fatty acids (Blesbois et al., 1997a,b; Kelso et al., 1997b).The effects of the various dietary oils on the recipient birds are not confined to changes in the fatty acid composition of the tissues (Surai et al., 1999) and semen (current study). Feeding birds with the tuna orbital oil diet without supplementation with excess vitamin E resulted in a marked depletion of vitamin E from the tissues. Presumably this depletion is due to the increased peroxidative susceptibility of tissues enriched with the highly polyunsaturated 22:6n-3, which places excessive demands on the antioxidant capacity of the bird. It is also evident that the antioxidant capacity of the semen can be compromised by the highly polyunsaturated dietary oils, as indicated by the reduction in vitamin E concentration in semen of the birds fed the tuna orbital oil (low vitamin E) diet. Moreover, the susceptibility of semen to lipid peroxidation in vitro was increased as a result of feeding the oils rich in 20:4n-6 or 22:6n-3 with the lower level of vitamin E, an effect that was effectively prevented by the inclusion of supplementary vitamin E in the diet. However, the dietary effects on the peroxidative susceptibility of the semen did not produce significant differences in fertilizing ability as assessed by artificial insemination.Among the multifarious consequences of feeding chickens with oils that provide diverse polyunsaturate profiles, the generation of increased concentrations and disparate compositions of eicosanoids may be relevant to the changes in sperm output. Arasco oil provides large amounts of 20:4n-6 for potential conversion to type 2 prostaglandins and type 4 leukotrienes, whereas tuna orbital oil provides substrate for the synthesis of type 3 prostaglandins and type 5 leukotrienes after the retroconversion of 22:6n-3 to 20:5n-3 (Lands, 1979; Fischer, 1989; Smith, 1989; Sardesai, 1992). Although prostaglandins in seminal plasma regulate various aspects of sperm function (Gottlieb and Bygdeman, 1988), their relevance to the present findings is unclear, especially since a range of prostaglandins has been shown to inhibit spermatogenesis in rodents (Abbatiello et al., 1976). Other possible mechanisms whereby dietary fatty acids could promote spermatogenesis, such as the regulation of gene expression (Jump and Clarke, 1999), remain to be examined. An important consideration is the potential interaction of polyunsaturated fatty acids or their derived eicosanoids with the hypothalamo-pituitary-gonadal axis and the hormonal control of spermatogenesis (De Kretser, 1990; Etches, 1996). Thus, the effects of dietary polyunsaturates on the secretion of GnRH, LH, FSH and testosterone, and on the responsiveness of the relevant types of cells to these hormones, may be worthy of investigation.Irrespective of the unde...

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