Browsing by Author "Speake, Brian K."

Now showing 1 - 3 of 3

Interspecies Variation in Yolk Selenium Concentrations Among Eggs of Free-Living Birds: the Effect of Phylogeny
(Elsevier Gmbh, Urban & Fischer verlag, 2006) Pappas, Athanasios C.; Karadas, Filiz; Surai, Peter F.; Wood, Nicholas A. R.; Cassey, Phillip; Bortolotti, Gary R.; Speake, Brian K.
Birds deposit the trace element selenium (Se) into their eggs because an adequate supply of this micronutrient is essential for embryonic development. Although there is considerable interest in egg Se with regard to topics as diverse as poultry nutrition and environmental pollution, data on the natural levels of Se in eggs of free-living avian species are currently very limited. To address this lack of information, we measured the yolk Se concentrations in eggs of 14 avian species collected in the wild. The concentrations (ng/g wet yolk) varied from 394 to 2238, with a mean value of 1040. Values (means +/- SD) for eggs from the UK, Canada and New Zealand were, respectively, 522 +/- 192 (3 species), 1194 +/- 584 (8 species) and 1147 +/- 200 (3 species). However, analysis by appropriate statistical models indicates that the effect of phylogenetic relatedeness among these species is so significant that it removes any effect of geographical location. In particular, species belonging to the order Passeriformes displayed significantly higher yolk Se levels than Non-Passeriforme species. In marked contrast to the free-living species, our previously published data indicate that the Se concentration in egg yolk of the domestic chicken is only about 100 ng/g wet yolk when the birds are maintained on a basal commercial diet without supplementary Se. The results reveal an extensive interspecies variation in yolk Se (across a 6-fold range) for eggs collected from the wild. Nevertheless, the Se concentrations in the yolks of all the free-living species were far higher (4-21-fold) than that achieved in the yolk of the domestic chicken consuming a standard basal diet. (c) 2006 Elsevier GrnbH. All rights reserved.
Metabolic Fates of Yolk Lipid and Individual Fatty Acids During Embryonic Development of the Coot and Moorhen
(Elsevier Science inc, 2007) Pappas, Athanasios C.; Karadas, Filiz; Wood, Nicholas A. R.; Speake, Brian K.
There is currently little information regarding the metabolic fates of yolk lipid and individual fatty acids during embryonic development of free-living avian species. Here we report the pattern of lipid utilization during embryonic development of the coot (Fulica atra) and the moorhen (Gallinula chloropus), two related species producing precocial offspring from eggs with a distinctive fatty acid composition and with an incubation period similar to that of the chicken. By the time of hatching, the proportions of the initial yolk lipid that had been transferred to the embryo were 88.2% and 79.8% for the coot and moorhen respectively. During the whole incubation period, 42.9% and 40.0% of the initial yolk lipid of the coot and moorhen respectively were lost from the system due to oxidation for energy, equating to 47.8% and 50.0% respectively of the actual amount of lipid transferred over this time. Thus, the lipid received by the embryos of both species is partitioned almost equally between the alternative fates of energy metabolism and incorporation into tissue lipids. In the coot, this 50:50 split between oxidation and tissue formation was maintained during the hatching process. The proportions of arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) in the yolk lipids of these species were 2.5-3.5 times higher than in eggs of domestic poultry. In contrast to the situation in the chicken, there was no preferential uptake of 22:6n-3 from the yolk during coot and moorhen development. The fatty acid compositions of the whole body lipids of the coot and moorhen hatchlings were almost identical to those of the initial yolks indicating that, unlike the chicken, these species display relatively little overall biomagnification of 20:4n-6 and 22:6n-6 during development. It is suggested that the yolk fatty acid profiles of the coot and moorhen are particularly well matched to the requirements of the embryo, reducing the need for selective uptake of 22:6n-3 and for the overall biomagnification of 22:6n-3 and 20:4n-6. (c) 2007 Elsevier Inc. All rights reserved.
Protective Effect of Modified Glucomannans and Organic Selenium Against Antioxidant Depletion in the Chicken Liver Due To T-2 Toxin-Contaminated Feed Consumption
(Elsevier Science inc, 2007) Dvorska, Julia E.; Pappas, Athanasios C.; Karadas, Filiz; Speake, Brian K.; Surai, Peter F.
The aim of this work was to assess the effect of T-2 toxin on the antioxidant status of the chicken and to study possible protective effects of modified glucomannan (Mycosorb (TM)) and organic selenium (Sel-Plex (TM)). Inclusion of T-2 toxin in the chickens' diet (8.1 mg/kg for 21 days) was associated with significant decreases in the concentrations of selenium (Se)(by 32.2%), et-tocopherol (by 41.4%), total carotenoids (by 56.5%), ascorbic acid (by 43.5%) and reduced glutathione (by 56.3%) in the liver, as well as a decrease in the hepatic activity of Se-dependent glutathione peroxidase (Se-GSH-Px) (by 36.8%). However, inclusion of modified glucomannans into the T-2 toxin-contaminated diet provided a partial protection against the detrimental effects of the mycotoxin on the antioxidant defences in the chicken liver. For example, the Se concentration in the liver was restored completely, although the Se-GSH-Px activity in the liver increased to only 81% of its control value. These protective effects of modified glucomannas were associated with a 45% reduction of lipid peroxidation in the liver in comparison to the effects of T-2 toxin alone. A combination of modified glucomannas with organic Se was shown to provide further protection against toxin-induced antioxidant depletion and lipid peroxidation in the chicken liver. Thus, the data clearly indicate a major protective effect of the mycotoxin-binder in combination with organic Se against the detrimental consequences of T-2 toxin-contaminated feed consumption by growing chickens. (c) 2007 Elsevier Inc. All rights reserved.