Carotenoids in Avian Nutrition and Embryonic Development. 2. Antioxident Properties and Discrimination in Embryonic Tissues

Repeatability of laboratory measurements for maternally derived yolk carotenoid concentrations in bird eggs

We describe a source of variability in maternally derived yolk carotenoids that is not routinely calculated in published studies. We quantify the measurement error in yolk carotenoid concentrations that may accrue during the analysis of yolk contents from repeat extractions and repeat high performance liquid chromatography (HPLC) runs of the same egg yolk sample from free range clutches of four farm bird species in New Zealand. We show that the variability between different eggs is substantially greater than the variability between replicate yolk extractions and HPLC analyses. Importantly, our results provide confidence to researchers that technical repeatability is a lesser concern when studying the biological differences between yolk samples.

Tissue-specific distribution of carotenoids and vitamin E in tissues of newly hatched chicks from various avian species

The aim of this study was to evaluate carotenoid and vitamin E distribution in egg and tissues of newly hatched chicks from wild mallard (Anas platyrhynchos), game pheasant (Phasianus colchicus), free-range guinea fowl (Numida meleagris), hen (Gallus domesticus) and domestic duck (Anas platyrhynchos) and intensively housed hens. Carotenoid concentrations in the egg yolk of free-range guinea fowl, pheasant and wild mallard were similar (61.3-79.2 microg/g). Egg yolks from ducks and intensively housed hens were characterised by the lowest carotenoid concentration comprising 11.2-14.8 microg/g. However, carotenoid concentration in eggs from free-range ducks and hens was less than half of that in free-range guinea fowl or pheasant. Depending on carotenoid concentration in the livers of species studied could be placed in the following descending order: free living pheasant>free-range guinea fowl>>free-range hen>>intensively housed hen>wild mallard>>housed duck>free-range duck. The carotenoid concentrations in other tissues of free-range guinea fowl and pheasant were substantially higher than in the other species studied. Egg yolk of housed hens was characterised by the highest alpha- and gamma-tocopherol concentrations. In accordance with the alpha-tocopherol concentration in the egg yolk, the birds can be placed in the following descending order: intensively housed hen>wild mallard>free-living pheasant>free-range duck>free-range hen=free-range guinea fowl>housed duck. The main finding of this work is species- and tissue-specific differences in carotenoid and vitamin E distribution in the various avian species studied.

Effects of carotenoid availability during laying on reproduction in the blue tit

Carotenoids are antioxidant pigments involved in several physiological processes and signalling in animals that cannot synthesise them and therefore must acquire them from food. We experimentally investigated the effects of carotenoid availability in the diet during egg laying on antioxidant deposition in egg yolk and the related effects on nestling condition, female body condition and parental investment in the blue tit (Parus caeruleus). Carotenoid supplementation of egg-laying females resulted in a significant increase in carotenoid concentration in egg yolk, but not in vitamin E or A concentration. There was no relationship between yellow plumage colour of adult females and carotenoid deposition in eggs, and no differential effect of feeding treatment depending on female colour. Nestlings from eggs laid by carotenoid supplemented females had longer tarsi, had faster development of the immune system as reflected by leukocyte concentration in blood, and grew brighter yellow feathers than nestlings from control females. However, nestlings from the two groups did not differ significantly in body mass, plasma antioxidants or plumage colour hue. At the time of chick rearing, carotenoid-fed females had increased plasma vitamin E levels compared to controls. However, females from the two treatment groups did not differ significantly in body condition or feeding rate. These results suggest that carotenoid availability is limiting during egg laying, and that females may have to balance the benefits of investing in egg quality against the potential costs of impairing their own future antioxidant protection. In addition, there may be considerable variation in carotenoid availability not only across seasons, but also among different stages of the breeding season.

Antioxidants, radiation and mutation as revealed by sperm abnormality in barn swallows from Chernobyl

Reduced levels of antioxidants such as carotenoids and vitamins A and E can increase DNA damage caused by free radicals. Exposure to radiation has been proposed to reduce levels of antioxidants that are used for DNA repair and this reduction may be responsible for increased levels of mutation in radioactively contaminated areas. We test this hypothesis using field measures of antioxidants in blood, liver and eggs of the barn swallow Hirundo rustica while relating these to levels of mutation as reflected by the frequency of abnormal sperm. Antioxidant levels in blood, liver and eggs were reduced in Chernobyl, Ukraine, compared with an uncontaminated control area, and levels of antioxidants correlated negatively with levels of background radiation. The frequency of abnormal sperm was almost an order of magnitude higher in Chernobyl than in the control area and was negatively related to antioxidant levels in blood and liver. This is consistent with the hypothesis of a direct link between radiation and individual levels of antioxidants, suggesting that levels of mutation differ among individuals owing to individual differences in the abundance of antioxidants.

Effects of maternal dietary supplementation with three sources of carotenoids on the retinyl esters of egg yolk and developing quail liver

The effects of supplementation of the maternal diet of quail with three natural sources of carotenoids (alfalfa nutrient concentrate (PX agrotrade mark), tomato powder and marigold extract) on the accumulation of retinol and retinyl esters in egg yolk and in the liver of the new hatchling and maternal were investigated. The present study showed that the vitamin A in quail egg yolk was present in 4 different forms, namely retinol (R 52-62%), retinyl linoleate (RL 9-11%), retinyl stearate (RS 4%), retinyl oleate (RO 11-15%) and retinyl palmitate (RP 13-22%). The retinyl ester profile of the liver of newly hatched quail (R 2-4%, RL 8-12%, RS 19-21%, RO 12-15%, RP 50-55%) differs from that of egg yolk but was similar to that of the liver of adult quail (R 1%, RL 5-6%, RS 21-28%, RO 9-12%, RP 54-63%). It has been shown that RO and RP concentrations in egg yolk and the liver of day old quail chick significantly increased as a result of carotenoid supplementation of the maternal diet.

Antioxidant systems of the developing quail embryo are compromised by mycotoxin aurofusarin

The effects of aurofusarin in the quail diet on the antioxidant systems of the developing embryo are investigated. Thirty eight 45-day-old Japanese quails (Coturnix japonica) were divided into two groups and were fed on a corn-soya diet or the same diet supplemented with aurofusarin at the level of 26.4 mg/kg feed in the form of Fusarium graminearum culture enriched with aurofusarin. Eggs obtained after 7 weeks of feeding were incubated. Samples of quail tissues were collected at day 17 of embryonic development and from day old hatchlings. Antioxidants and malondialdehyde were analysed by HPLC-based methods. Inclusion of aurofusarin in the maternal diet was associated with decreased concentrations of alpha- and gamma-tocopherols, alpha- and gamma-tocotrienols, retinol, lutein and zeaxanthin in egg yolk. The vitamin E (tocopherols and tocotrienols) concentration in the liver and yolk sac membrane (YSM) of the day 17 embryos and the hatchlings from aurofusarin-fed group was significantly decreased. Alpha-tocopherol concentration was also reduced in kidney, lung, heart, muscle and brain of day-old quails. In the liver of day-old quails, concentrations of lutein, zeaxanthin, retinol, retinyl linoleate, retinyl oleate, retinyl palmitate and retinyl stearate were also reduced. As a result of these diminished antioxidant concentrations, tissue susceptibility to lipid peroxidation was significantly increased. It is suggested that a compromised antioxidant system of the egg yolk and embryonic tissues could predispose quails to increased mortality at late stages of their embryonic development.

Carotenoids and egg quality in the lesser blackbacked gull Larus fuscus: a supplemental feeding study of maternal effects

Egg quality is a phenotype of, and can profoundly influence fitness in, both mother and offspring. However, the physiological mechanisms that underlie this maternal effect are poorly understood. Carotenoids are hypothesized to enhance antioxidant activity and immune function, and are responsible for the pigmentation of egg yolk. The proximate basis and consequences of this maternal investment, however, have not previously been studied in wild birds. In this supplemental feeding study of lesser black-backed gulls, Larus fuscus, carotenoid-fed females are shown to have increased integument pigmentation, higher plasma concentrations of carotenoids and antioxidant activity, and lower plasma concentrations of immunoglobulins (Igs) in comparison with controls. In turn, carotenoid-fed females produced eggs containing high carotenoid but low Ig concentrations (i.e. passive immunity), whereas control females produced eggs containing low carotenoid but high Ig concentrations. Within-clutch patterns of these resources varied over the laying sequence in a similar manner in both carotenoid-fed and control nests. Our results suggest that carotenoids could be one resource responsible for egg quality maternal effects in birds. We discuss the possible implications of carotenoid-mediated effects on phenotype for fitness in mothers and their offspring.