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The aim of this review is to collate data relevant to understanding the evolution of viviparity in general, and complex placentae in particular. The wide range of reproductive modes exhibited by lizards provides a solid model system for investigating the evolution of viviparity. Within the lizards are oviparous species, viviparous species that have a very simple placenta and little nutrient uptake from the mother during pregnancy (lecithotrophic viviparity), through a range of species that have intermediate placental complexities and placental nutrient provision, to species that lay microlecithal eggs and most nutrients are provided across the placenta during development (obligate placentotrophy). In its commonest form, lecithotrophic viviparity, some uptake of water, inorganic ions and oxygen occurs from the mother to the embryo during pregnancy. In contrast, the evolution of complex placentae is rare, but has evolved at least five times. Where there is still predominantly a reliance on egg yolk, the omphaloplacenta seems to be paramount in the provision of nutrition to the embryo via histotrophy, whereas the chorioallantoic placenta is more likely involved in gas exchange. Reliance on provision of substantial organic nutrient is correlated with the regional specialisation of the chorioallantoic placenta to form a placentome for nutrient uptake, particularly lipids, and the further development of the gas exchange capabilities of the other parts of the chorioallantois.

Carotenoids in the diet of the laying hen are incorporated into the egg yolk and subsequently into the liver and other tissues or the chicken embryo. Since these pigments are known to provide a range of health benefits to a variety of animals, it is of interest to know whether the effects of maternally derived carotenoids are strictly limited to the embryonic period or if they persist in the progeny after hatching. The aim of this study is to compare the effectiveness of pre-hatch (from the hen's diet) with that of post-hatch (from the progeny's diet) supplementation with carotenoids on the carotenoid status of the chick during the first 4 weeks of post-hatch life. Hens were fed a control diet or a diet supplemented with a carotenoid-rich extract of alfalfa. Eggs front the supplemented hens contained up to 22 times more carotenoids than the controls. The concentration of carotenoids in the livers of chicks hatching from the enriched eggs was initially 29 times greater than in the control chicks. Hepatic carotenoid concentrations in chicks from enriched eggs maintained post-hatch on the control diet were sustained at higher values compared with chicks from control eggs that were fed post-hatch on the carotenoid-supplemented diet, for at least the first 7 days. However, by 14 days, the latter group had overtaken the former in terms of liver carotenoid levels, Thus. under these conditions, maternal effects predominate for at least the first week after hatching, whereas from 2 weeks onwards, the progeny's diet becomes the main determinant of its carotenoid status. Since the antioxidant and immunostimulatory roles of carotenoids are likely to be especially important during the immediate post-hatch period, maternal dietary intake of carotenoids may have important ramifications for the viability of the offspring.,(c) 2005 Elsevier Inc. All rights reserved.

During avian development, lipoproteins derived from yolk lipid are assembled in the yolk sac membrane (YSM) for secretion into the embryonic circulation. To investigate how yolk polyunsaturated fatty acids, essential for the development of certain tissues, are distributed among the lipid classes of the lipoproteins, pieces of YSM were incubated in vitro with [14C]arachidonic and [14C]docosahexaenoic acids (DHA). There was a marked difference in the partitioning of these two precursors among the lipid classes of the tissue. Of the radioactivity incorporated into total lipid from [14C]-arachidonic acid during 1 h of incubation, 67.3% was esterified as phospholipid and 29.5% as triacylglycerol. In contrast, only 14.6% of the label incorporated from [14C]-DHA was esterified as phospholipid, whereas 73.2% was recovered in triacylglycerol. This pattern of differential partitioning was observed at all time points and across a 20-fold range of fatty acid concentrations. There was no evidence for conversion of the radioactive arachidonic and DHAs to other fatty acids prior to incorporation into tissue lipids. It is suggested that the selective incorporation of yolk-derived DHA into the triacylglycerol of secreted lipoproteins represents part of a mechanism for directing this polyunsaturate to particular embryonic tissues.

Energy metabolism during embryonic development of snakes differs in several respects from the patterns displayed by other reptiles. There are, however, no previous reports describing the main energy source for development, the yolk lipids, in snake eggs. There is also no information on the distribution of yolk fatty acids to the tissues during snake development. In eggs of the water python ( Liasis fuscus), we report that triacylglycerol, phospholipid, cholesteryl ester and free cholesterol, respectively, form 70.3%, 14.1%, 5.7% and 2.1% of the total lipid. The main polyunsaturate of the yolk lipid classes is 18:2n-6. The yolk phospholipid contains 20:4n-6 and 22:6n-3 at 13.0% and 3.6% (w/w), respectively. Approximately 10% and 30% of the initial egg lipids are respectively recovered in the residual yolk and the fat body of the hatchling. A major function of yolk lipid is, therefore, to provision the neonate with large energy reserves. The proportion of 22:6n-3 in brain phospholipid of the hatchling is 11.1% (w/w): this represents only 0.24% of the amount of 22:6n-3 originally present in the egg. This also contrasts with values for free-living avian species where the proportion of DHA in neonatal brain phospholipid is 16-19%. In the liver of the newly hatched python, triacylglycerol, phospholipid and cholesteryl ester, respectively, form 68.2%, 7.7% and 14.3% of total lipid. This contrasts with embryos of birds where cholesteryl ester forms up to 80% of total liver lipid and suggests that the mechanism of lipid transfer in the water python embryo differs in some respects from the avian situation.

The aim of this study was to evaluate effects of modified glucomannans (Mycosorb) on egg yolk and liver of the day-old quail after aurofusarin inclusion in the maternal diet. Fifty-four 45-day-old Japanese quail were divided into three groups and were fed ad libitum a corn-soya diet balanced in all nutrients. The diet of the experimental quail was supplemented with aurofusarin at the level of 26.4 mg/kg feed in the form of Fusarium graminearum culture enriched with aurofusarin or with aurofusarin plus Mycosorb at 1 g/kg feed. Eggs obtained after 8 weeks of feeding were analysed and incubated in standard conditions of 37.5 degrees C/55% RH. Samples of quail liver were collected from day-old hatchlings. Main polyunsaturated fatty acids (PUFAs) of the egg yolk were analysed by gas chromatography, and tocopherols and tocotrienols were analysed by HPLC-based methods. Inclusion of aurofusarin in the maternal diet was associated with decreased proportions of docosahexaenoic acid and increased proportions of linoleic acid in major lipid fractions of the egg yolk as well as with decreased concentrations of alpha- and gamma-tocopherols, alpha- and gamma-tocotrienols in egg yolk and liver of a day-old quail. Inclusion of modified glucomannans (Mycosorb) into the quail diet simultaneously with aurofusarin showed a significant protective effect against changes in PUFA and antioxidant composition in the egg yolk and liver of quail. It is suggested that a combination of mycotoxin adsorbents and natural antioxidants could be the next step in counteracting mycotoxins in animal feed.

Docosahexaenoic acid (DHA) (22:6n−3) is a polyunsaturated fatty acid that is an essential constituent of membranes, particularly of the nervous system. Infants acquire DHA from their mothers, either prenatally via the placenta or postnatally in milk. The present study aimed to test the hypothesis that maternal supplementation during the second and third trimesters of pregnancy enriches maternal and/or fetal DHA status. In a randomised, prospective, double-blind study 100 mothers received either fish-oil capsules containing 400mg DHA/g (200mg/d) (n50), or placebo containing 810mg oleic acid/g (400mg/d) (n50) from 15 weeks gestation until term. Venous blood samples were obtained from mothers at 15, 28 and 40 weeks, and from the umbilical cord at birth. Total fatty acids in plasma and erythrocytes were analysed by GC–MS. There were no significant differences between maternal groups in baseline DHA, as a proportion of total fatty acids (g/100g total fatty acids) or concentration (nmol/ml), in plasma and erythrocytes. DHA concentrations in plasma at 28 weeks (P=0·02) and erythrocytes at both 28 weeks (P=0·03) and term (P=0·02) were 20% higher in supplemented mothers than the placebo group. DHA accounted for a higher proportion of total fatty acids in erythrocytes of supplemented mothers at 28 weeks (P=0·003) and term (P=0·01). There were no significant differences between groups in DHA (g/100g total fatty acids or nmol/l) in cord blood. Maternal DHA status was maximal in mid-trimester and declined to term, at a lower rate in supplemented compared with unsupplemented mothers. Maternal DHA supplementation significantly increases maternal DHA status and limits the last trimester decline in maternal status, aiding preferential transfer of DHA from mother to fetus.

Because the yolk lipids of the king penguin (Aptenodytes patagonicus) contain the highest concentrations of long-chain n-3 polyunsaturated fatty acids yet reported for an avian species, the consequences for the establishment of the brain's fatty acid profile in the embryo were investigated. To place the results in context, the fatty acid compositions of yolk lipid and brain phospholipid of the king penguin were compared with those from three other species of free-living birds. The proportions of docosahexaenoic acid (22:6n-3; DHA) in the total lipid of the initial yolks for the Canada goose (Branta canadensis), mallard (Anas platyrhynchos), moorhen (Gallinula chloropus), and king penguin were (% w/w of fatty acids) 1.0+/-0.1, 1.9+/-0.2, 3.3+/-0.1, and 5.9+/-0.2, respectively. The respective concentrations of DHA (% w/w of phospholipid fatty acids) in brains of the newly hatched chicks of these same species were 18.5+/-0.2, 19.6+/-0.7, 16.9+/-0.4, and 17.6+/-0.1. Thus, the natural interspecies diversity in yolk fatty acid profiles does not necessarily produce major differences in the DHA content of the developing brain. Only about 1% of the amount of DHA initially present in the yolk was recovered in the brain of the penguin at hatch. There was no preferential uptake of DHA from the yolk during development of the king penguin.

The switch from yolk to food (myctophid fishes) as the nutrient source for the newly hatched chick of the king penguin ( Aptenodytes patagonicus) results in a profound change in the pattern of fatty acid provision. This is characterized by major increases in the proportionate intake of n-3 polyunsaturates (20:5n-3 and 22:6n-3) and long chain (C(20-24)) monounsaturates, accompanied by relatively lower levels of n-6 polyunsaturates (18:2n-6 and 20:4n-6). The effects of this change on the fatty acid composition of tissue lipids during the first month of growth, a period of tissue maturation leading to thermal emancipation, were determined. The composition of adipose tissue triacylglycerol responded rapidly to the switch in nutrient source, the proportion of long chain monounsaturates (mainly 20:1n-9 and 22:1n-11) increasing five-fold between hatch and emancipation while the relative levels of 20:5n-3 and 22:6n-3 also increased significantly, by 3- and 1.2-fold, respectively. At emancipation, the fatty acid profile of adipose tissue triacylglycerol was essentially identical to that of the diet. At hatch, the main polyunsaturates of muscle phospholipid were 20:4n-6, 20:5n-3, and 22:6n-3, respectively, forming (w/w of fatty acids) 13.2%, 5.0%, and 12.0%. By emancipation, 20:4n-6 had decreased to 4.8%, 20:5n-3 increased to 10.9%, and 22:6n-3 at 11.4% showed little change. The main polyunsaturate in brain phospholipid at hatch was 22:6n-3 (19.3%): this remained almost constant until day 15 but then increased significantly to 23.6% by emancipation. Significant but minor changes in the proportions of 20:4n-6 (from 5.2% at hatch to 3.5% at emancipation) and 20:5n-3 (from 3.0% to 3.9%) were also observed in brain phospholipid. The data do not allow us to completely distinguish changes that are solely diet driven from those which are a consequence of tissue differentiation. Nevertheless, it is evident that, whereas the fatty acid composition of adipose tissue responds faithfully to the change in nutrient source, the phospholipids of muscle and, especially, of brain are much more refractory to the effects of diet during this period of tissue maturation.

Most reptiles are oviparous, with the developing embryos relying on the contents of the yolk to sustain development until hatching (lecithotrophy). The yolk is composed primarily of lipid and protein, which act as an energy source and the essential components to build embryonic tissue. Nevertheless, yolk and the resulting embryos contain many other nutrients, including inorganic ions, vitamins, carotenoids, water and hormones. Apart from water and oxygen, which may be taken up by eggs, and some inorganic ions that can come from the eggshell or even from outside the egg, everything required by the embryo must be in the egg when it is laid. Approximately 20% of squamate reptiles are viviparous, exhibiting a variety of placental complexities. Species with complex placentae have reduced yolk volumes, with the mother augmenting embryonic nutrition by provision across the placenta (placentotrophy). Despite assumed advantages of placentotrophy, only 5 out of approximately 100 lineages of viviparous squamates exhibit substantial placentotrophy. This paper reviews available and recent information on the yolk contents of a variety of squamate reptiles to ask the question, how are nutrients transported from the yolk to the embryo or across the placenta? Although, current available data suggest that, in broad terms, yolk is taken up by embryos without discrimination of the nutrients, there are some apparent exceptions, including the very long chain polyunsaturated fatty acids. In addition, fundamental differences in the patterns of energy utilisation in lizards and snakes suggest fundamental differences in lipid profiles in these taxa, which appear to reflect the differences between placentotrophic and lecithotrophic viviparous lizards.

Since the yolk lipids of the king penguin (Aptenodytes patagonicus) naturally contain the highest concentrations of DHA and EPA yet reported for the eggs of any avian species, the effects of this (n-3)-rich yolk on the FA profiles of the embryonic heart and skeletal muscle were investigated. The concentrations (mg/g wet tissue) of phospholipid (PL) in the developing heart and leg muscle of the penguin doubled between days 27 and 55 from the beginning of egg incubation (i.e., from the halfway stage of embryonic development to 2 d posthatch), whereas no net increase occurred in pectoral muscle. During this period, the concentration of TAG in heart decreased by half but increased two- and sixfold in leg and pectoral muscle, respectively. The most notable change in cholesteryl ester concentration occurred in pectoral muscle, increasing ninefold between days 27 and 55. Arachidonic acid (ARA) was the major polyunsaturate in PL of the penguin's heart, where it formed about 20% (w/w) of FA at day 55. At the equivalent developmental stage, the heart PL of the chicken contained a 1.3-fold greater proportion of ARA, contained a fifth less DHA, and was almost devoid of EPA, whereas the latter FA was a significant component (7% of FA) of penguin heart PL. Similarly, in PL of leg and pectoral muscle, the chicken displayed about 1.4-fold more ARA, up to 50% less DHA, and far less EPA in comparison with the penguin. Thus, although ARA-rich PL profiles are achieved in the heart and muscle of the penguin embryo, these profiles are significantly affected by the high n-3 content of the yolk.

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.

1. The effect of the mycotoxin aurofusarin on the antioxidant composition and fatty acid profile of quail eggs was investigated. 2. Thirty eight 45-d-old Japanese quails were divided into two groups (experimental and control, 15 females +4 males in each group) and were fed on a maize-soya diet balanced in all nutrients. The diet of the experimental quails was supplemented with aurofusarin at the level of 26.4 mg/kg feed in the form of Fusarium graminearum culture enriched with aurofusarin. At the beginning and after 2, 4 and 8 week supplementation periods, eggs were collected and analysed. After 8 weeks of supplementation, experimental quails were fed on unsupplemented diet during the next 4 weeks and eggs were collected after 2 and 4 weeks on such a diet and analysed. 3. Aurofusarin caused a significant (P

Piscivorous birds consume diets which are rich in highly-polyunsaturated n-3 fatty acids; these play vital roles in embryonic development but are very susceptible to oxidative damage. The effects of such diets on the fatty acid composition and antioxidant content of the yolk were investigated in the northern gannet Morus bassanus, the great skua Catharacta skua, the American white pelican Pelecanus erythrorhynchos and the double-crested cormorant Phalacrocorax auritus. The phospholipid fraction of the eggs of these four species contained high proportions of the n-3 fatty acid, docosahexaenoic acid, which formed 7.5‐11.3% (w/w) of the fatty acids of this fraction. The presence of eicosapentaenoic and docosapentaenoic acids also contributed to the total n-3 content of the phospholipid. The n-6 polyunsaturate, arachidonic acid, formed between 8% and 19% (w/w) of the phospholipid fatty acids. For the pelican and cormorant, this is consistent with the consumption of freshwater fishes in which arachidonic acid may be a significant acyl constituent. This finding is, however, more difficult to explain for the gannet and skua which largely consume marine fish with a low arachidonic acid content. The yolks of all four species contained relatively high concentrations of vitamin E (90.2‐302.3 m gg 71 wet yolk) which was mainly present as a-tocopherol. The eggs of the pelican and cormorant were especially enriched in carotenoids (150.9 and 115.7 m gg 71 wet yolk, respectively).

The concentrations (microg/g wet yolk) of total carotenoids in eggs of the common moorhen (Gallinula chloropus), American coot (Fulica americana) and lesser black-backed gull (Larus fuscus), collected in the wild, were 47.5, 131.0 and 71.6, respectively. In contrast to data for eggs of the domestic chicken, beta-carotene was a significant component in the yolks of these three wild species, forming 25-29% by wt. of the total carotenoids present. The concentration of total carotenoids in the livers of the newly-hatched chicks was 5-10 times higher than in the other tissues and beta-carotene was again a major component, forming 37-58% of the hepatic carotenoids. In the newly-hatched gull, the proportions of both lutein and zeaxanthin were very low in the liver but high in the heart and muscle when compared with the yolk. By contrast canthaxanthin, echinenone and beta-carotene were very minor constituents of heart and muscle when compared with their proportions in the yolk of the gull. The proportions of lutein and zeaxanthin in the liver of the newly-hatched coot and moorhen were also far lower than in the yolk whereas the liver was relatively enriched with beta-cryptoxanthin, beta-carotene and (in the moorhen) echinenone. The results indicate that avian embryos discriminate between different carotenoids during their distribution from the yolk to the various tissues.

This study examines the transfer of lipids from the yolk to the embryo of the king penguin, a seabird with a high dietary intake of n–3 fatty acids. The concentrations of total lipid, triacylglycerol (TAG), and phospholipid (PL) in the yolk decreased by ∼80% between days 33 and 55 of development, indicating intensive lipid transfer, whereas the concentration of cholesteryl ester (CE) increased threefold, possibly due to recycling. Total lipid concentration in plasma and liver of the embryo increased by twofold from day 40 to hatching due to the accumulation of CE. Yolk lipids contained high amounts of C20–22n–3 fatty acids with 22:6(n–3) forming 4 and 10% of the fatty acid mass in TAG and PL, respectively. Both TAG and PL of plasma and liver contained high proportions of 22:6(n–3) (∼15% in plasma and >20% in liver at day 33); liver PL also contained a high proportion of 20:4(n–6) (14%). Thus both 22:6(n–3) and 20:4(n–6), which are, respectively, abundant and deficient in the yolk, undergo biomagnification during transfer to the embryo.

Niveoscincus ocellatus is an important species in historical analyses of the evolution of viviparity because it is the species upon which the type II chorioallantoic placenta was based. Here we describe the net nutrient uptake across the placenta of N. ocellatus for comparison with other species of skinks with complex placentae. N. ocellatus is highly placentotrophic, with neonates being 1.68-times larger in dry matter than the fresh eggs. There is an increase of nitrogen from 6.3 +/- 0.2 mg to 9.2 +/- 0.6 mg, and ash from 3.8 +/- 0.3 mg to 6.7 +/- 0.6 mg. The increase in ash is made up by a more than two-fold increase in the amounts of calcium, potassium and sodium. There is no significant difference in lipids in the neonates compared to fresh eggs, so considerable lipid must have crossed the placenta to provide energy for embryonic development. N. ocellatus is significantly more placentotrophic than Niveoscincus metallicus, which also has a complex chorioallantoic placenta. Discovery of substantial placentotrophy in this genus confirms that two lineages of Australian lygosomine skinks (represented by the genera Pseudemoia and Niveoscincus) have evolved this pattern of embryonic nutrition and supports the hypothesis that the evolution of reptilian placentotrophy involves specialisations in addition to structural modifications of the chorioallantoic placenta.

We have reviewed published and new quantitative data on the net uptake of nutrients by embryos of oviparous and viviparous lizards that vary in chorioallantoic placental complexity to better understand the evolution of complex placentae. We assessed net nutrient uptake during embryonic development by measuring the total dry mass, or the mass of separate nutrients, in the egg at about the time of ovulation and in the neonate. There is no significant difference in the fresh egg to neonate dry mass ratio of oviparous and viviparous species that have simple placentae, indicating that there is little, if any, net uptake of nutrients by viviparous species with simple chorioallantoic placentae. In contrast, there is significant uptake of dry matter and individual nutrients across the placenta of species with complex chorioallantoic placentae. Species of the genus Niveoscincus have a range of placentae and nutrient uptakes, even among populations of one species, suggesting that further studies among populations of single species are required. Data are available for relatively few clades, and all the data for the three most complex chorioallantoic placental types are derived from a single genus. Thus, further research on new genera of lizards is required to overcome the potentially confounding effects of phylogeny in our analyses.

Recent studies on chicken semen have suggested that the lipid and fatty acid composition of spermatozoa may be important determinants of fertility. Phospholipid fatty acid composition, vitamin E content and in vitro susceptibility to lipid peroxidation of duck spermatozoa were investigated using GC-MS and HPLC based methods. The total phospholipid fraction of duck spermatozoa was characterized by high proportions of the n-6 polyunsaturated fatty acids arachidonic (20:4n-6), docosatetraenoic (22:4n-6) and docosapentaenoic (22:5n-6) acids but a substantial proportion of the n-3 fatty acid docosahexaenoic (22:6n-3) acid was also present. Palmitic (16:0) and stearic (18:0) fatty acids were the major saturates in sperm phospholipids. Among the phospholipid classes, phosphatidylserine (PS) had the highest degree of unsaturation due to very high proportions of 22:6n-3, 22:5n-6, 22:4n-6 and 20:4n-6, comprising together more than 75% of total fatty acids in this fraction. Phosphatidylethanolamine (PE) also contained high proportions of these four C 20–22 polyunsaturates, which together formed 60% of total fatty acids in this phospholipid. Spermatozoa and seminal plasma of duck semen were characterized by unexpectedly low content of vitamin E, being more than 4-fold lower than in chicken semen. In duck semen the major proportion of the vitamin E (>70%) was located in the spermatozoa. The very high proportion of 22:6n-3 in PS and PE fractions of duck sperm lipids and the comparatively low levels of vitamin E could predispose semen to lipid peroxidation. Nevertheless the in vitro susceptibilities to Fe 2+ -stimulated lipid peroxidation of duck and chicken spermatozoa were very similar. The results of the study suggest that increased superoxide dismutase and glutathione peroxidase activity and increased antioxidant activity of seminal plasma may compensate for the low levels of vitamin E to help protect the membranes of duck spermatozoa, which exhibit a high degree of unsaturation from oxidative stress.

Lipid analysis was performed on freshly ovulated eggs (n = 5) of the oviparous lizard Bassiana duperreyi. The fresh weight of the whole egg contents was 132.0 +/- 4.3 mg (mean +/- SE) of which lipid constituted 21.9 +/- 1.1% (w/w). Triacylglycerol formed an exceptionally high proportion (85.4 +/-0.5%, w/w) of the total lipid, whereas phospholipid, free cholesterol, cholesteryl ester, and free fatty acid, respectively, contributed 11.2 +/- 0.3, 1.4 +/- 0.1, 1.3 +/- 0.1, and 0.6 +/- 0.1% of the total lipid mass. Linoleic and alpha-linolenic acids were the major polyunsaturates of the triacylglycerol fraction, respectively, forming 16.3 +/- 0.1 and 8.3 +/- 0.1% (w/w) of the fatty acids. Linoleic acid was the major fatty acid (29.0 +/- 0.1%) of the total phospholipid, which also contained substantial amounts of arachidonic (6.4 +/- 0.1%) and eicosapentaenoic (3.0 +/- 0.1%) acids, but a relatively low proportion (1.6 +/- 0.1%) of docosahexaenoic acid. Phosphatidylcholine formed the major phospholipid class (73.8 +/- 2.3%) w/w of total phospholipid) and was enriched in linoleic acid, whereas phosphatidylethanolamine, which formed 20.4 +/- 1.9%(w/w) of total phospholipid, contained higher proportions of arachidonic and docosahexaenoic acids.

The ion, energy, lipid, nitrogen and fat-soluble vitamin contents of freshly ovulated eggs and neonates of the viviparous lizard Niveoscincus metallicus were measured to quantify uptake of nutrients across the placenta. This species is particularly interesting because it has a chorio-allantoic placenta that is intermediate in complexity compared to viviparous species that have been the focus of other studies. Newly ovulated eggs have a wet mass of 79.6+/-4.6 mg and a dry mass of 41.8+/-2.8 mg, compared to the neonates that have a wet mass of 224.2+/-8.2 mg and dry mass of 37.9+/-1.2 mg. Thus, there is no significant net uptake of dry matter across the placenta. Neonates have significantly less lipid (6.2+/-0.4 mg) than eggs (12.7+/-0.5 mg), but no significant difference in nitrogen (4.1+/-0.3 mg) compared to eggs (4.5+/-0.2 mg). Energy densities reflect the protein and lipid composition and the relative dry masses of the eggs and neonates. There is significantly more energy (1029.1+/-80.0 J) in the egg than in the neonate (858.2+/-38.6 J). The increase in the ash content of the neonates (2.9+/-0.2 mg) compared to fresh eggs (2.1+/-0.3 mg) was not significant, even though there was an approximately threefold increase in the amount of sodium (0.11+/-0.01 mg in neonates, 0.34+/-0.01 mg in eggs) and potassium (0.12+/-0.017 in neonates, 0.40+/-0.01 mg in eggs) in neonates compared to eggs. There was no significant uptake of calcium and magnesium during development. The egg lipids consisted of triacylglycerol (66.7+/-2.3 %), phospholipid (18.9+/-0.7 %), cholesteryl ester (4.9+/-1.6 %) and free cholesterol (5.6+/-1.5 %). The egg phospholipid contained comparatively high proportions of arachidonic and eicosapentanoic acids but low levels of docosahexaenoic acid (DHA), whereas the phospholipid of the neonate was greatly enriched in DHA. In the egg, the predominant vitamin E was (agr;)-tocopherol (62.6+/-3.4 mg g(-)(1)), although there was some (ggr;)-tocotrienol (3.5+/-0.3 mg g(-)(1)), and vitamin A was present (1.5+/-0.2 mg g(-)(1)). The ratio of neonate dry mass to egg dry mass of N. metallicus (0.91) lies between that of species with type I (0.78) and type III (1.70) chorio-allantoic placentae, confirming our conclusion that the placenta of N. metallicus is functionally intermediate, as well as intermediate in complexity, between these other two types.

The aim of this study was to assess the differences in yolk lipid composition of pheasants and geese between birds maintained in captivity on commercial grain-based diets and their counterparts in the wild which are free to select their diets from the environment. The most striking difference was that the proportion of α-linolenic acid (18:3n-3) was far greater in all yolk lipid classes [triacylglycerol (TAG), phospholipid (PL), cholesteryl ester (CE)] of the wild birds than in the captive birds of both species. For example, in yolk TAG, the level (wt.% of total fatty acids) of 18:3n-3 was only 1.6% in eggs of captive pheasants compared with 27.9% in eggs of the wild birds. The proportions of 18:3n-3 in yolk TAG of housed, free-range and feral geese were 0.6, 6.6 and 19.3% respectively. It is suggested that these differences arise from the predominance of linoleic acid (18:2n-6) as the major polyunsaturate in the commercial grain-based feeds whereas geese and pheasants in the wild consume grasses and green shoots in which 18:3n-3 is the main fatty acid. The concentrations of vitamin E and carotenoids in the yolks of the free-range and feral geese were much greater than in those of the housed geese. Thus the developing embryos of pheasants and geese in the wild will have access to far higher levels of n-3 polyunsaturates and lipid-soluble antioxidants compared with embryos of the housed birds.

Energy, ionic, protein and lipid contents and fatty acid profiles for the major lipid classes of freshly ovulated eggs and neonates of the viviparous lizard, Pseudemoia spenceri, were measured. Litter size is 1.7 ± 0.1, with larger females producing larger neonates. Placentotrophy results in approximately 23% more dry matter in the neonates than in the fresh egg. The increase in the quantity of protein and lipid during development is not significant and is reflected in the similarity of energy densities of eggs and neonates. As a percentage of dry matter, neonates have slightly lower proportions of lipid and protein than eggs because of significant uptake of ash, calcium, potassium and sodium, but not of magnesium, across the placenta. The amounts of triacylglycerol and phospholipid are not significantly different between the egg and the neonate, but neonates contain significantly more cholesterol and cholesteryl ester. The amounts of the major fatty acids, palmitic and oleic acids, recovered from the total lipids of the neonate do not differ significantly from the amounts present in the egg lipids, but the neonates contain significantly less linoleic and α-linolenic acids and more palmitoleic, stearic and arachidonic acids than the eggs. The amount of docosahexaenoic acid recovered from the lipids of the neonate is 2.6-times greater than the amount initially present in the egg. P. spenceri has a relatively larger egg and a smaller reliance on placentotrophy than other species in the same genus, all of which have a similar placental morphology. Nevertheless, the pattern of embryonic nutrition includes both obligative and facultative placentotrophy. All the major components of yolk of oviparous species are present in eggs of P. spenceri, but most are augmented during development by placental transfer.

Differences between four avian species of commercial importance (chicken, turkey, duck and goose), in terms of the relationship between the dietary fatty acids supplied in the diet of the layers and the fatty acid composition of the egg yolk lipids, were investigated. Laying hens of the four species were provided with diets with very similar fatty acid compositions. The polyunsaturated fatty acid content of the diets consisted of linoleic and α-linolenic acids at approximately 50% and 6% (w/w of total fatty acids), respectively, for all four species. In spite of the very similar dietary provision of fatty acids, the subsequent fatty acid profiles of the yolk lipids differed markedly between the four species. In particular, the proportion of docosahexaenoic acid in the total lipid of the yolk was three to five times greater for the chicken compared to the other three species. By contrast, the proportion of arachidonic acid in total yolk lipid was approximately two times greater for the goose and duck than for the chicken and turkey. Thus the chicken was more efficient at incorporating long-chain (C22 ) fatty acid of the n-3 series into yolk lipid whereas the duck and goose preferentially incorporated C20 fatty acid of the n-6 series. The turkey eggs contained a similar proportion of arachidonic acid but less docosahexaenoic acid than the chicken eggs. The main differences between the avian species in terms of the yolk levels of C20 –22 polyunsaturated fatty acids were in the phospholipid fraction since only low levels of these fatty acids were present in the triacylglycerol fraction. The relative proportions of docosahexaenoic acid in the phospholipid and triacylglycerol fractions of the livers of the newly-hatched chicks of the four species reflected the differences displayed by the yolks. The proportions of arachidonic acid in these liver lipid fractions, however, did not reflect the species differences in yolk lipid composition. © 1999 Society of Chemical Industry

The activity of acyl-coA:cholesterol acyltransferase, the enzyme responsible for the conversion of free cholesterol to cholesteryl ester, was measured in the microsomal fraction of the yolk sac membrane of the alligator ( Alligator mississippiensis ) embryo at various stages of development. For embryos developing at 33°C, the activity of the enzyme (pmol cholesteryl ester synthesised min −1 mg microsomal protein −1 ) increased from 368.3±78.3 at day 30 to 1584.8±46.2 at day 50 of development when using the cholesterol endogenous to the microsomes as substrate. The addition of an optimal concentration of exogenous cholesterol to the assay mixture stimulated the activity by nearly two-fold at day 40 but produced no significant stimulation at days 50 and 60. Cholesteryl ester hydrolase activity was very low in the microsomes and undetectable in the cytosol at all stages. Also, the cytosol contained a factor which inhibited cholesteryl ester hydrolase. Thus the enzymic capacity of the yolk sac membrane is strongly directed towards the net esterification of incoming yolk-derived cholesterol.

The aim of this study was to determine the major nutritive components present in fresh eggs of the freshwater turtle, Emydura macquarii , and to investigate the utilisation of these components during embryonic development. Comparison of the compositions of the initial egg contents (yolk plus albumen), the hatchling and the residual yolk indicated that embryonic development was accompanied by the loss of approximately 15% of the initial dry matter, 25% of the energy content, 8.8% of the protein and 41% of the lipid. Thus, in addition to oxidation of fatty acids, some of the energy consumed during development (17.6%) was derived from catabolism of protein. A feature of the yolk lipids was the presence of high proportions of α -linolenic acid (18:3n-3), particularly in the triacylglycerol and a high concentration of α -tocopherol, similar to than in the yolk of birds. The yolk phospholipid contained a high concentration of arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) but a relatively low amount of docosahexaenoic acid (DHA) (22:6n-3). By contrast, the phospholipid of the hatchling was enriched in DHA but contained only a small concentration of eicosapentaenoic acid, suggesting the possible conversion of eicosapentaenoic acid to DHA by the embryo. The amount of calcium recovered in the hatchling was almost twice that of the initial egg contents suggesting mobilisation of calcium from the shell.

The lipids of the yolk represent the primary nutrient source for the chick embryo, providing over 90% of the energy required for development as well as supplying a range of structural components for membrane biogenesis. Since the energy needs and the requirements for particular fatty acids differ greatly among the various embryonic tissues and between successive developmental stages, the regulated distribution of lipid components from the yolk to the different body sites forms a central feature of this system. As a consequence, the various tissues of the newly hatched chick display a range of highly characteristic lipid and fatty acid compositions in accordance with their functions but which, in many cases, also reflect the intensity and complexity of the lipid transfer process in the embryo. For example, the liver of the chick contains very high levels of cholesteryl ester as a result of the mechanism of lipid transfer. Moreover, the triacylglycerol fraction of the liver is highly enriched in docosahexaenoic acid, possibly reflecting hepatic involvement in the transfer of this fatty acid to the brain. The accretion of large amounts of both docosahexaenoic and arachidonic acids in the phospholipids of the brain and retina is a key feature of chick embryo development, the importance of which is underlined by the expression of a series of mechanisms, possibly mediated by the liver and adipose tissue, designed to promote the transfer of these fatty acids to the neural tissues.

The aim of this study was to investigate the possibility of biodiscrimination between different forms of vitamin E during the development of the chick embryo. The vitamin E present in the initial yolk consisted of alpha-tocopherol (90%), (beta + gamma)-tocopherol (8%), alpha-tocotrienol (0.3%) and (beta + gamma)-tocotrienol (1.3%). In marked contrast, the vitamin E recovered from the bile of the day-16 embryo contained much higher proportions of alpha-tocotrienol (10%) and especially of (beta + gamma)-tocotrienol (42%). By the time of hatching, 56% of the vitamin E present in the bile was in the form of (beta + gamma)-tocotrienol. The residual yolk of the newly-hatched chick contained far greater proportions of alpha-tocotrienol (2.6%) and (beta + gamma)-tocotrienol (10%) than were present in the initial yolk. The results suggest that the liver of the embryo may selectively excrete tocotrienols as components of bile, whilst retaining the tocopherols within the hepatocytes. The increased proportions of tocotrienols in the residual yolk may result from the recycling of bile from the gall bladder to the yolk. The liver of the day-old chick contained alpha-tocopherol as the main form of vitamin E (90%) with only a small proportion (0.2%) of (beta + gamma)-tocotrienol. The alpha-tocopherol form was also the main vitamin E component in the brain (85%), heart (79%), lung (82%) and adipose tissue (91%) of the day-old chick. The present study suggests the occurrence of a high degree of biodiscrimination between tocopherols and tocotrienols during the development of the chick embryo.

Laying hens were placed on either a control diet or a carotenoid-supplemented diet. The subsequent concentrations of carotenoids in the yolks of the newly laid fertile eggs (μg carotenoid/g fresh yolk) were 13.3 and 41.1 on the control diet and high-carotenoid diet, respectively. For the day-old chicks derived from the high-carotenoid group, the carotenoid levels in the yolk sac membrane, liver, and plasma were approximately 3 times greater than in the control group; however, the other tissues were less responsive. The proportion of lutein (% wt/wt of total carotenoids) was far lower in the liver of the chick than in the yolk. However, in the non-hepatic tissues the proportion of lutein was generally higher than in the yolk. This suggests that discrimination between different carotenoids may occur in the embryo. For the high-carotenoid group, the peroxidative susceptibility of extracts of the yolk, yolk sac membrane, and liver was decreased compared with samples from the control group. Thus, carotenoids may provide antioxidant protection to the tissues.

Although substantial information is available regarding the fatty acid composition of lipids of the yolk and of the developing tissues of the chicken embryo, there is little knowledge on this topic for other avian species. The aim of the present study was to compare the yolk and embryonic tissue fatty acid profiles for a species selecting its food in the wild (the lesser black backed gull) with one fed on a standard commercial diet (the commercially reared pheasant). The fatty acid compositions of the yolk lipids were determined, and major differences were observed between the two species. In particular, the phospholipid of the gull yolk was enriched in 20:4n-6 and 22:6n-3 (18.8 and 7.1%, respectively, by weight of total fatty acids) in comparison with the pheasant (4.0 and 4.1%, respectively). The fatty acid compositions of the embryonic tissues were determined using eggs incubated in the laboratory. For the liver and heart, the fatty acid composition of the lipids in the two species reflected the initial yolk composition, with the gull tissue lipids generally containing higher proportions of 20:4n-6 and 22:6n-3 than those of the pheasant. In contrast, the fatty acid profiles of the brain phospholipid were essentially identical in the two species, with 20:4n-6 and 22:6n-3 comprising approximately 9 and 17%, respectively, of total fatty acids in both cases.

A comparative study has been made of the major lipid fractions and their fatty acid compositions in the yolk of eggs from ostriches under wild and farmed conditions. There were no differences in the lipid contents and proportions of the lipid fractions between the two groups of yolks. In both groups of yolks triacylglycerol and phospholipid were the major fractions. In the eggs from the wild ostriches, all the lipid fractions displayed substantial concentrations of C18 polyunsaturated fatty acids, triacylglycerol being particularly rich in linolenic acid and phospholipid rich in linoleic acid; phospholipid displayed substantial concentrations also of C20 and C22 polyunsaturates. There were considerable differences in the fatty acid compositions between the yolks. Those from the farmed birds displayed lower proportions of C18 polyunsaturates, particularly linolenic acid, throughout the lipid fractions. Compensatory increases were displayed most obviously in the concentrations of oleic acid and palmitoleic acid as well as other acids. The distinctive and extensive changes in fatty acid composition, particularly relating to the polyunsaturates, are discussed with respect to overall dietary requirements and specificities for embryo metabolism and possible effects on reproductive performance.

The concentrations of vitamin E, vitamin A, selenium, reduced glutathione and the activities of glutathione peroxidase and superoxide dismutase were determined in the yolk, yolk sac membrane, liver and brain of the developing chick embryo. The changes in the concentrations of vitamins E and A in the yolk and liver during development were consistent with the occurrence of a preferential transfer of vitamin A from the yolk to the embryo before day 14 of incubation, whereas the main period of vitamin E transfer occurred later, during the last week of incubation. The concentrations of reduced glutathione in the yolk sac membrane, liver and brain were similar at all developmental stages studied. However, the levels of the other measured antioxidant systems were very much higher in the liver than in the brain. Thus, in the newly hatched chick, the levels of vitamin E, vitamin A, selenium, glutathione peroxidase and superoxide dismutase were, respectively, 58.0-, 174.7-, 3.6-, 4.0- and 4.7- fold higher in the liver than in the brain when expressed on the basis of tissue fresh weight.

Fertile eggs obtained from alligators reared in captivity typically exhibit high rates of embryonic mortality. Also, the fatty acid composition of the yolk lipid of the captive eggs is markedly different from that observed in eggs from wild alligators, possibly as a result of differences in maternal diet in the two situations. The fatty acid compositions of tissue lipids during the embryonic development of wild and captive alligators were compared. The lipids of liver, adipose tissue and heart of the two types of embryo displayed fatty acid profiles which generally reflected the acyl compositions of the respective yolks. Thus the lipids from these tissues of the captive embryos contained markedly higher proportionate levels of linoleic and linolenic acids, lower levels of palmitoleic acid, and, in general, lower levels of docosahexaenoic acid and other C20 and C22 polyunsaturates, in comparison to the values for the wild embryos. In contrast, the fatty acid composition of the brain phosphoglycerides was very similar in the two types of embryo. Thus, at least in those embryos which had survived during the developmental period studied, the brain was able to maintain a relatively constant fatty acid composition, in spite of major differences between the wild and captive eggs in the proportions of the various fatty acids supplied from the yolk. It is suggested that a major cause of embryonic mortality in the captive embryos could be a failure to maintain an adequate level of docosahexaenoic acid in the developing brain.

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.

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.

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.

The primary purpose of this study is to determine the extent to which the effects of dietary supplementation of the female chicken with selenium (Se) continue into the next generation. An additional aim is to compare the relative effectiveness of pre-hatch (from the hen's diet) with that of post-hatch (from the progeny's diet) supplementation with Se on the Se status of the chick during the first 4 weeks of post-hatch life. Hens were maintained on control or Se-supplemented diets, respectively containing 0.027 and 0.419 mu g Se/g of feed. The high-Se diet elevated the Se content of the hens' eggs by 7.1-fold. At hatch, the concentrations of Se in the liver, breast muscle and whole blood of the chicks originating from the high-Se parents were, respectively, 5.4-, 4.3- and 7.7-fold higher than the values in the chicks of the low-Se parents. When the offspring from the two parental groups were both maintained on the low-Se progeny diet, the tissue Se concentrations in chicks originating from the high-Se hens remained significantly higher for 3-4 weeks after hatching, compared with the values in chicks from the low-Se hens. Similarly, tissue glutathione peroxidase activity remained significantly higher in chicks from the high-Se hens for 2-4 weeks post-hatch. Thus, the effects of maternal Se supplementation persist in the progeny for several weeks after hatching. However, when chicks hatching from low-Se eggs were placed on a high Se diet, their tissue Se concentrations at 7 days of age were markedly higher than the values in chicks from high-Se eggs placed on the low-Se diet. (c) 2005 Elsevier Inc. All rights reserved.

The antioxidant capacity of the avian intestinal mucosa is potentially important in protecting the gut wall from the harmful actions of reactive oxygen species originating from the diet, mucosal metabolism and the inflammatory response to enteric microbes. To assess this capacity, we determined the total lipid-soluble and water-soluble antioxidant activities of mucosal extracts, using tissue from different parts of the intestinal tract of the chicken. The lipid-soluble antioxidants, vitamin E and carotenoids, were also measured in the same samples. Total lipid-soluble antioxidant activity was highest in mucosa from the duodenum followed by the jejunum, with much lower activities in the ileum, ceca and colon. Total water-soluble antioxidant activity of the mucosa was at least an order of magnitude greater than the lipid-soluble activity under the assay conditions and did not differ significantly among the different parts of the intestinal tract. High concentrations of vitamin E were present in the mucosa of the duodenum and jejunum, with a trend to lower levels in the ileum and ceca, and significantly less in the colon. Similarly, the mucosa of the duodenum and jejunum contained the highest concentrations of carotenoids, with much lower levels in the ileum and colon. The different isoforms of vitamin E were absorbed from the digesta by the mucosa without any major selectivity. However, the liver was greatly enriched with alpha-tocopherol over the other isoforms, indicating a high degree of discrimination by this tissue. The results indicate major differences in the relative contributions of lipid- and water-soluble antioxidants in the mucosa along the different parts of the intestinal tract, most likely reflecting the sites of vitamin E and carotenoid absorption. (c) 2005 Elsevier Inc. All rights reserved.

During gestation in the viviparous lizard Pseudemoia entrecasteauxii , the fetus obtains nutrients from two sources: uptake of yolk components from the retained egg (lecithotrophy) and transfer of nutrients from the maternal circulation via the placenta (placentotrophy). Although net placentotrophy in this species is indicated by the observation that the neonate contains 1.7 times more dry matter than the egg, the placental transfer of lipid has not been previously demonstrated. Lipid analysis was performed on newly ovulated eggs and on neonates. The weight of total lipid per neonate (8.2±0.5 mg) is significantly ( P =0.049) greater than that in the egg (6.8±0.4 mg), indicating that the placenta must contribute some lipid to the fetus. On the assumption that 50% of the lipid delivered to the fetus from either source is oxidized for energy, it is calculated that the placenta accounts for 58.5% of the fetal lipid requirements, with the remaining 41.5% being derived from the egg. The fatty acid compositions of the triacylglycerol and phospholipid recovered in the neonatal tissue differ substantially from those of the egg. In particular, the proportions of 18:2 n −6 and 18:3 n −3 are far lower in the neonatal lipids compared with the egg lipids. On the other hand, the proportion of 22:6 n −3 in the phospholipid of the neonate is six times higher than in the phospholipid of the egg. The absolute amount (mg) of 22:6 n −3 recovered in the total lipid of the neonate is 3.8 times greater than the amount initially present in the egg. By comparison, the amount of total fatty acid in neonatal lipid is 1.2 times greater than the amount in the egg. Thus, there is a preferential use of 22:6 n −3 for tissue phospholipid synthesis during development. We conclude that there is net transfer of fatty acids across the placenta to the fetus of P. entrecasteauxii and a high degree of selectivity in the use of the various fatty acids for fetal tissue lipid synthesis.

The yolk fatty-acid profiles of a range of species of insectivorous scincid lizards generally conform to a common pattern, typified by high proportions of linoleic acid (13.5-18.5% of total fatty acids), substantial proportions of alpha-linolenic acid (2.4-8.2%), and significant amounts of the long-chain polyunsaturated fatty acids, arachidonic (1.6-3.3%), eicosapentaenoic (0.7-1.2%) and docosahexaenoic (0.7-1.6%) acids. We characterised the fatty-acid compositions of ten prey taxa that are eaten by female skinks during vitellogenesis. Linoleic acid is the major polyunsaturated fatty acid in all prey, excepting Orthoptera where alpha-linolenic acid predominates. To varying extents, alpha-linolenic acid is present in all the prey items. Arachidonic acid forms over 1% of total fatty acids for six of the prey items. Four of the prey items contain eicosapentaenoic acid at over 1%. Most notably, docosahexaenoic acid is essentially absent from all the prey items. There is a general similarity between the fatty-acid profiles of prey and yolk, suggesting that the linoleic, alpha-linolenic, arachidonic and eicosapentaenoic acids required for egg formation can be supplied directly from the maternal diet. However, the docosahexaenoic acid of the egg lipids cannot derive from the diet and must, therefore, be formed by biosynthesis in the maternal liver, using dietary alpha-linolenic and eicosapentaenoic acids as precursors.

The yolk sac membrane (YSM) of the chicken embryo is known to express delta-9 and delta-6 desaturase activities, suggesting that biosynthesis of the unsaturated fatty acids 18:1n-9, 20:4n-6 and 22:6n-3 might occur during the transfer of yolk lipids across the YSM. If so, this biosynthesis could help to satisfy the demands of the embryonic tissues for these unsaturates. To assess the ability of the YSM to perform these conversions, pieces of the tissue were incubated in vitro with the precursor fatty acids, 14C-18:0, 14C-18:2n-6 or 14C-18:3n-3, and the recovery of radioactivity in the respective products, 18:1n-9, 20:4n-6 and 22:6n-3, was determined. After 4 h of continuous incubation, radioactivity from these precursors was incorporated primarily into triacylglycerol and phospholipid of the tissue pieces. Only small proportions (0.3-4.7%) of this incorporated radioactivity were, however, recovered as 18:1n-9, 20:4n-6 or 22:6n-3. The majority of the incorporated label was retained in the form of the precursor fatty acids. After a 1-h pulse incubation with the 14C precursors, followed by a 3-h chase incubation in the absence of exogenous label, the conversion of incorporated radioactivity to the end product unsaturates was again relatively low (0.5-8.1%). Thus, although conversions of the precursors to the end product fatty acids were detectable in this system, the biosynthesis of these unsaturates is apparently a quantitatively minor pathway in the YSM. Nevertheless, since the amount of 18:2n-6 in the yolk lipids far exceeds that of 20:4n-6, the conversion of even a small proportion of the former to the latter fatty acid could significantly increase the supply of 20:4n-6 to the embryonic tissues.

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.

The transfer of lipid from the yolk to the avian embryo is mediated by the yolk sac membrane (YSM). Some, but not all, of the published morphological evidence supports the view that the lipid undergoes a cycle of hydrolysis and re-esterification during translocation across the YSM. The present study aims to test this view by investigating the capacity of the YSM to perform esterification of free fatty acids to form acyl-lipids. YSM pieces (area vasculosa), obtained from the chicken embryo at day 10 of development, were incubated in vitro in medium containing [14C]-palmitic acid. Radioactivity was rapidly incorporated into the tissue lipid indicating a high capacity for esterification. The incorporation was linear with time during the 1-h incubation. Approximately 84% of the incorporated label was recovered in triacylglycerol, 12% was incorporated into phospholipid and less than 1% was detected in cholesteryl ester. [14C]-palmitic acid was incorporated primarily at the sn-1/3 positions in the triacylglycerol molecule and at the sn-1 position of phospholipid. The incorporation of label into tissue pieces obtained from the non-vascularized peripheral region of the YSM (area vitellina) was much more limited than that observed for the area vasculosa. The results support the hypothesis that yolk lipid is hydrolyzed and re-esterified during transfer across the YSM.

Since the yolk lipids of the king penguin (Aptenodytes patagonicus) are rich in n-3 fatty acids, which are potentially susceptible to peroxidative damage, the yolk contents and yolk-to-embryo transfer of antioxidants and lipid-soluble vitamins were investigated under conditions of natural incubation in the wild. The concentration of vitamin E in the unincubated egg was 155 microg/g wet yolk, of which 88% was alpha-tocopherol and the rest was gamma-tocopherol. Vitamin A (2.9 microg/g) was present in the yolk entirely as retinol; no retinyl esters were detected. Throughout the latter half of the incubation period, vitamins E and A were taken up from the yolk into the yolk sac membrane (YSM) and later accumulated in the liver, with vitamin A being transferred in advance of vitamin E. In the YSM, vitamin A was present almost entirely as retinyl ester, indicating that the free retinol of the yolk is rapidly esterified following uptake. Retinyl esters were also the predominant form in the liver. The retinyl esters of the liver and YSM displayed different fatty acid profiles. At hatching, the brain contained relatively little vitamin E (4.7 microg/g) compared to the much higher concentration in the liver (482.9 microg/g) at this stage. Ascorbic acid was not detected in the yolk but was present at a high concentration in the brain at day 27 (404.6 microg/g), decreasing to less than half this value by the time of hatching. This report is the first to delineate the yolk-to-embryo transfer of lipid-soluble vitamins for a free-living avian species. The yolk fatty acids of the king penguin provide an extreme example of potential oxidative susceptibility, forming a basis for comparative studies on embryonic antioxidant requirements among species of birds whose yolk lipids differ in their degree of unsaturation.

The major lipid classes, their fatty acid profiles, and the amounts of the lipid-soluble components, vitamin E, vitamin A, and carotenoids, were determined for egg yolks of the Hermann's tortoise (Testudo hermanni boettgeri) with the aim of identifying any features that may potentially impair the adaptation of this endangered species to deteriorations in habitat. Total lipid formed 16% (wt/wt) of the fresh yolk and consisted of (wt/wt) 74.4% triacylglycerol, 18.1% phospholipid, 3.0% cholesteryl ester, and 3.4% free cholesterol. Despite a diet based on green plants, contributing alpha-linolenic acid as the main polyunsaturate, this fatty acid formed only 3.8% of the total mass of fatty acid of the total lipid. The main acyl component of the yolk lipids was the monounsaturated fatty acid, oleic acid, which formed 45.6% of the total. The most striking feature of the yolk composition was the almost complete lack of two nutrients, docosahexaenoic acid and vitamin A, which are essential for the developing embryo. Although it is feasible that the embryo synthesizes docosahexaenoic acid from yolk-derived alpha-linolenic acid and also converts yolk-derived beta-carotene to vitamin A, the yolk is poorly endowed with both these precursors. The stringencies displayed by the yolk composition in this species may limit the flexibility to adapt to changes in the availability of food items when the habitat is threatened. Zoo Biol 20:75-87, 2001. Copyright 2001 Wiley-Liss, Inc.

The contents of eggs and neonates of the Australian skinks, Lampropholis guichenoti and L. delicata, are described and compared to allow interpretation of nutrient utilisation by the developing embryo. Even though the females are the same size, L. guichenoti lay smaller clutches of larger eggs (egg contents=41.6+/-1.2 mg dry mass) than L. delicata (26.6+/-2.8 mg). The energy density is the same for eggs (30.5+/-0.9 J/g ash-free dry mass for L. guichenoti and 29.9+/-1.1 J/mg for L. delicata) and neonates (22.5+/-1.3 J/mg for L. guichenoti and 23.5+/-0.4 J/mg for L. delicata) between species. The amount of nitrogen (protein) in neonates is only slightly lower than that in eggs, whereas there is a large and significant decline in total lipids. Thus, like some other skinks, protein is a source of metabolic energy during embryogenesis, although not as important as lipid. Triacylglycerol is the major lipid component of the eggs (80% of total lipid), with phospholipid forming only approximately 10% of the total lipid. The fatty acid profile of the phospholipid is distinguished by a high proportion of arachidonic acid (8%), a significant proportion of eicosapentaenoic acid (2-4%) and a relatively low proportion of docosahexaenoic acid (2-3%) compared to chickens. Eggs of both species have remarkably low concentrations of free cholesterol compared to other amniote eggs (0.7% for L. guichenoti and 1.3% for L. delicata). The loss of lipid during embryonic development is almost entirely due to the selective utilisation of yolk triacylglycerol, presumably for energy. By contrast, the amount of phospholipid recovered from the neonates was the same as that originally in the eggs. Moreover, significantly more total cholesterol was present in the neonates than in the eggs, suggesting that biosynthesis of additional cholesterol occurred during development. The phospholipids of the neonates contain higher proportions of arachidonic (11-12%) and docosahexaenoic (8%) acids than the phospholipids of the eggs. Eicosapentaenoic acid is less prevalent in phospholipids in neonates than in eggs. Neonates of both species contain significantly more calcium than the fresh egg contents (L. guichenoti, eggs 0.303+/-0.051 mg, neonates 0.641+/-0.047 mg; L. delicata, eggs 0.187+/-0.013 mg, neonates 0.435+/-0.033 mg), presumably as a result of resorption of calcium from the eggshell. Interestingly, there is also significantly more sodium in neonates than in the contents of fresh eggs (L. guichenoti, eggs 0.094+/-0.010 mg, neonates 0.184+/-0.011 mg; L. delicata, eggs 0.084+/-0.011 mg, neonates 0.151+/-0.010 mg). There is no significant difference in the content of potassium and magnesium in eggs and neonates of either species. Although the fresh eggs of L. delicata have a significantly higher sodium concentration than L. guichenoti, there is no difference in the concentrations of calcium, magnesium, potassium or sodium in the neonates of the two species.

Eulamprus tympanum is a high-altitude viviparous lizard that was probably used to help define a Type I chorioallantoic placenta. In this article, we (1) describe the net transport of nutrients across the placenta of E. tympanum, and (2) compare placental uptake in E. tympanum with a previous study of Eulamprus quoyii, which occurs in warmer environments, to assess the potential importance of thermal regime on placentotrophy. Freshly ovulated eggs are 387.3+/-19.7 mg. There is a significant net uptake of water and a net loss of dry matter during development, so the dry neonate is only 84% the size of the dry egg. There is no significant change in the total ash or nitrogen in eggs during embryonic development, with the entire loss of dry matter being lipid. Almost the entire loss of lipid occurs in the triacylglycerol fraction, with no net change in phospholipids. A net increase in total cholesterol suggests that cholesterol is synthesised by the developing embryo. The lipid profile of eggs of E. tympanum reflects that of other species with simple placentae in having a relatively high proportion of triacylglycerol and little cholesterol. The fatty acid composition of eggs reflects that expected in the diet of E. tympanum. There is a preservation and some synthesis of arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids in the phospholipid fraction during embryonic development. Despite there being no net uptake of ash, there is a net increase in calcium, potassium, sodium, and magnesium in the neonate compared with the egg. We conclude that E. tympanum, like E. quoyii, is predominantly lecithotrophic with little, if any, uptake of organic molecules but with significant uptake of some inorganic ions and water. In addition, there is no difference in placentotrophy correlated with differences in the environments inhabited by each species.

The salient feature of the fatty acid profile of kestrel eggs collected in the wild was the very high proportion of arachidonic acid (15.2% 0.7% of fatty acid mass, np5) in the phospholipid fraction of the yolk. Kestrels in captivity fed on dayold chickens produced eggs that differed from those of the wild birds in a number of compositional features: the proportion of linoleic acid was increased in all the lipid fractions; the proportion of arachidonic acid was increased in yolk phospholipid and cholesteryl ester; the proportion of a-linolenic acid was decreased in all lipid classes, and that of docosahexaenoic acid was decreased in phospholipid and cholesteryl ester. Partridge eggs from the wild contained linoleic acid as the main polyunsaturate of all the yolk lipid fractions. Captive partridges maintained on a formulated diet very rich in linoleic acid produced eggs with increased levels of linoleic, arachidonic, and n-6 docosapentaenoic acids in the phospholipid fraction; reduced proportions of a-linolenic acid were observed in all lipid classes, and the proportion of docosahexaenoic acid was markedly reduced in the phospholipid fraction. Thus, captive breeding of both the kestrel and the partridge increases the n-6/n-3 polyunsaturate ratio of the yolk lipids.