Alterations in lipid composition of plasma lipoproteins during deposition of egg yolk

The profiles of total lipids and of the molecular species of individual lipid classes were compared among corresponding lipoproteins of plasma and yolk of the laying hen. A close qualitative correspondence was found in the makeup of the molecular species of glycerophospholipids and triglycerides of the very low density lipoproteins and the high density lipoproteins of plasma and yolk. There was a lower proportion of the trienoic triglycerides and of the dienoic glycerophospholipids in the egg yolk than in the plasma lipoproteins, and the greatest differences (20-30%) were noted between the high density lipoproteins. It was also observed that the plasma high density lipoproteins lost their cholesteryl esters upon entering the yolk. On the basis of these and comparable analyses of the plasma lipoproteins of the nonlaying hen, it is concluded that the laying hen synthesizes specific lipoproteins for deposition in the yolk, and these are carried in plasma and selectively transferred to the developing ovum without significant equilibration with the other plasma lipoproteins.     

Potential of alfalfa as an alternative molt induction diet for laying hens: egg quality and consumer acceptability

Dietary molt induction to initiate additional egg laying cycles in commercial laying hen flocks is a wide spread practice in the United States. Feed deprivation is the most commonly used method but this practice has generated several concerns which has lead to research for viable alternative approaches. From a management standpoint a single ingredient molting diet consisting of high fiber-low energy represents an easily adaptable diet for large laying hen production units. Alfalfa meal is readily available in most commercial locations and possesses many of the desirable properties of an ideal laying hen molt diet. In the current study hens at a commercial laying facility were molted by both alfalfa and feed deprivation. After the hens had reentered post-molt commercial egg production, eggs were examined for egg quality performance. Egg shell strength, albumen height, yolk height, weight, length, and yolk color were all tested using various mechanical techniques. The eggs were also sampled for testing by consumer sensory panels that assessed the desirability of the eggs' color and flavor/texture. Eggs laid by hens molted by alfalfa had a significantly lower (p<0.05) "a*" level of colorimetry. Eggs laid by hens molted with alfalfa also exhibited significantly higher (p<0.05) egg weights and length. In the consumer sensory test, there was no significant difference (p>0.05) in color or flavor/texture scores in eggs from either feed deprived or alfalfa molted hens. The consumer sensory and mechanical quality attributes indicates that alfalfa shows promise as an alternative molt induction diet by providing a single diet option for extending egg production into a second egg laying cycle.     

Sex and immunity in the yellow dung fly Scathophaga stercoraria

The immune system is of increasing interest to evolutionary biologists. Immunity may trade-off against other fitness components, with recent work suggesting reproduction in particular impinges on immune defence. There may also be sex differences in the immune system. Additionally, while life history traits typically have low heritability, little is known about additive genetic variance of immunity. An insect's major defence against multicellular pathogens is to encapsulate the invader. Phenoloxidase (PO) is a key enzyme in the cascade resulting in the melanized capsule, and is often used to estimate resistance to an immune insult. We examined the effects of copulation, egg laying, sex and age on PO in Scathophaga stercoraria. We also measured the heritability of PO activity. The sexes differed in haemolymph PO activity and PO was significantly affected by age, but not by copulation or egg laying. There was significant heritable variation for haemolymph PO.     

Ovarian follicular development, lipid peroxidation, antioxidative status and immune response in laying hens fed fish oil-supplemented diets to produce n-3-enriched eggs

The objective of the present study was to research the effect of feeding laying hens fish oil-supplemented diets to produce n-3-enriched eggs on their ovarian follicular development, serum lipid peroxidation, antioxidative status and immune response. A total of 105 white Bovens hens at 24 weeks of age were housed in cages in an open-sided building under a 16 h light : 8 h dark lighting schedule. Birds were randomly divided into five treatments and were fed, ad libitum, diets containing 0% (control), 1.25%, 2.5%, 3.5% or 5.0% fish oil from 24 to 36 weeks of age. Egg production and weight were recorded. By weeks 35 and 36 of age 15 eggs were taken at random from each treatment to determine the yolk lipid profile and cholesterol content. At the end of the experimental period, 10 females from each treatment were randomly chosen, anaesthetised and killed by decapitation. Ovary and oviduct samples were immediately weighted and ovarian follicles were classified. Serum thiobarbituric acid-reactive substance (TBARS), hepatic TBARS and hepatic glutathione peroxidase (GSH-Px) activity were measured. No clear trend was observed concerning egg production and egg yolk cholesterol. As dietary fish oil levels increased, n-3-polyunsaturated fatty acids (n-3 PUFA) increased, whereas n-6 PUFA tended to decrease in yolk lipids. No negative effects were detected in ovary and oviduct weights, expressed in both absolute terms and relative to body weight. The numbers and total weights of large yellow follicles (LYF) in the ovary were not significantly affected by fish oil supplementation. Low levels (1.25% to 2.5%) of fish oil reduced both plasma and hepatic TBARS and enhanced GSH-Px activity. It is also interesting to note that inclusion of 2.5% fish oil in laying hen diets enhanced the antibody titre in laying hens. Therefore, it could be concluded that inclusion of fish oil in laying hen diets at moderate levels increased the n-3 fatty acids content in eggs, improved antioxidative status, enhanced the antibody response and did not have a negative influence on the different reproductive morphology parameters in laying hens.     

Some properties of acid lipase in the defatted liver from the laying hen (Gallus domesticus)

Acid lipase activity was found in the defatted liver from the laying hen, but little neutral or alkaline lipase activity was observed in the liver. Most of acid lipase was in the insoluble fraction of the defatted liver, and the enzyme was solubilized by sonication at 9 kHz for 50 min in a slightly alkaline solution. The lipase showed its maximum activity at pH 5.0, 38 degrees C. It was stable below 40 degrees C and over the pH range from 4.0 to 9.0. Detergents, serum of the laying hen and the soluble fraction from the defatted liver homogenate from the laying hen markedly inhibited the lipase activity. The lipase solubilized by sonication was large in molecular mass, suggesting that the preparation formed colloidal particles.     

Purification of β-N-Acetylhexosaminidase from Egg White and the Microsomal and Lysosomal Fractions of Hen Oviduct

β-N-Acetylhexosaminidase (NAHase) was purified from egg white and the lysosomal and microsomal fractions of hen oviduct. The purification procedure included affinity chromatography using Sepharose 4B coupled with IgG specific for NAHase of hen oviduct. The isoelectric points of the three enzymes were different, but their antigen determinants were identical. In sodium dodecyl sulfate polyacrylamide gel electrophoresis, both the egg white and lysosomal enzyme gave only one protein band each, corresponding to a MW of 68000 and 53000, respectively, but the microsomal enzyme gave two protein bands, corresponding to those of the lysosomal and egg white enzymes.     

Comparison of Different Methods for Preparation of Human Milk Casein

Changes of the estradiol and lipid concentrations in hen serum, and those in the fatty acids of hen and cockerel livers were studied during the maturing period. The concentrations of estradiol and lipid in serum reached a maximum level a few days before the onset of laying, and then fell. A marked increase in oleate, and decreases in stearate and arachidonate were observed in both the liver and serum lipids of the hen when reaching laying. The fatty acid compositions of the serum and liver of the hen at 145 and 167 days of age were close to those of yolk lipid. In the cockerel, high contents of stearate and arachidonate and a low content of oleate were observed, and the fatty acid composition did not change appreciably with age. On estrogenization of the male chick, the fatty acid cmposition of the liver lipid was similar to that of the laying hen liver. The ratio of the unsaturated fatty acid/saturated fatty acid in the liver of hen increased when reaching laying, the value at 167 days old being close to that of yolk lipid. This ratio in the liver lipid of cockerel did not change significantly throughout the experimental period.     

Carotenoids in eggs and plasma of red-legged partridges: effects of diet and reproductive output

Carotenoids are important dietary constituents in birds. They serve as pigments and play numerous physiological roles in both the laying hen and developing embryo. However, factors determining the absorption of carotenoids and their allocation to different functions are numerous and complex, and causal relationships are generally poorly known. Our objective was to determine the degree to which carotenoid levels in egg yolks and the plasma of hens were influenced by differences in diet and reproductive output in captive red-legged partridges. Carotenoid concentrations were measured by high performance liquid chromatography in two feeds (high and low carotenoid content) and in yolks and plasma of hens near the start and end of laying. Early in the laying season, plasma and yolk carotenoids varied with diet and were correlated with one another. Late in the season, a dietary effect was evident only for yolks, and there was no relationship between plasma and egg levels of individual hens. However, plasma carotenoids at the end of laying were strongly correlated with the number of eggs that had been laid. Dietary availability, although important, could explain some variation in carotenoid levels in plasma and egg yolks only in the context of reproductive history.     

Hydrolytic enzymes conjugated to quantum dots mostly retain whole catalytic activity

BackgroundTagging a luminescent quantum dot (QD) with a biological like enzyme (Enz) creates value-added entities like quantum dot–enzyme bioconjugates (QDEnzBio) that find utility as sensors to detect glucose or beacons to track enzymes in vivo. For such applications, it is imperative that the enzyme remains catalytically active while the quantum dot is luminescent in the bioconjugate. A critical feature that dictates this is the quantum dot–enzyme linkage chemistry. Previously such linkages have put constraints on polypeptide chain dynamics or hindered substrate diffusion to active site, seriously undermining enzyme catalytic activity. In this work we address this issue using avidin–biotin linkage chemistry together with a flexible spacer to conjugate enzyme to quantum dot.MethodsThe catalytic activity of three biotinylated hydrolytic enzymes, namely, hen egg white lysozyme (HEWL), alkaline phosphatase (ALP) and acetylcholinesterase (AChE) was investigated post-conjugation to streptavidin linked quantum dot for multiple substrate concentrations and varying degrees of biotinylation.ResultsWe demonstrate that all enzymes retain full catalytic activity in the quantum dot–enzyme bioconjugates in comparison to biotinylated enzyme alone. However, unlike alkaline phosphatase and acetylcholinesterase, the catalytic activity of hen egg white lysozyme was observed to be increasingly susceptible to ionic strength of medium with rising level of biotinylation. This susceptibility was attributed to arise from depletion of positive charge from lysine amino groups after biotinylation.ConclusionsWe reasoned that avidin–biotin linkage in the presence of a flexible seven atom spacer between biotin and enzyme poses no constraints to enzyme structure/dynamics enabling retention of full enzyme activity.General significanceOverall our results demonstrate for the first time that streptavidin–biotin chemistry can yield quantum dot enzyme bioconjugates that retain full catalytic activity as native enzyme.     

外源促性腺激素处理后鸡产蛋及孵化研究

目的：探讨促卵泡素（FSH）对低产期肉用种母鸡在产蛋数量和孵化的影响,寻求较佳的用于提高低产期母鸡产蛋的激素剂量。方法：本试验采用同种激素不同剂量的处理方式,比较实验组和对照组产蛋量和孵化情况。结果：注射不同剂量的激素对鸡的产蛋有一定的影响,实验组一的平均产蛋数与对照组接近,其它四组均显著低于对照组（P〈0．05）,孵化率与健雏率与对照组无显著差异（P〉0．05）。结论：小荆量激素处理对鸡产蛋量没有太大的影响,但大剂量会引起鸡生殖系统萎缩,激素处理对受精卵孵化及雏鸡生长并无负面影响。     

Reversible inactivation of avian lysozymes by dimethyl (2-hydroxy-5-nitrobenzyl)-sulfonium bromide

The reaction of hen egg white lysozyme with a 4 molar excess of dimethyl (2-hydroxy-5-nitrobenzyl)-sulfonium bromide at pH 6.0 leads to total loss of enzymatic activity within 5 minutes. Upon standing, the inactivated enzyme spontaneously regains activity, leveling off at 60% of the original activity after 72 hours. Under the same conditions, turkey egg white lysozyme is reduced to less than 5% of its original activity within 5 minutes, then spontaneously reactivates to 85% of its original activity after 24 hours. Human lysozyme shows no dramatic loss of activity when treated under these conditions. The presence of the substrate, chitotetraose, prevents the initial inactivation of both hen and turkey enzymes.     

Energy expenditure during egg laying is equal for early and late breeding free-living female great tits

In many bird populations, variation in the timing of reproduction exists but it is not obvious how this variation is maintained as timing has substantial fitness consequences. Daily energy expenditure (DEE) during the egg laying period increases with decreasing temperatures and thus perhaps only females that can produce eggs at low energetic cost will lay early in the season, at low temperatures. We tested whether late laying females have a higher daily energy expenditure during egg laying than early laying females in 43 great tits (Parus major), by comparing on the same day the DEE of early females late in their laying sequence with DEE of late females early in their egg laying sequence. We also validated the assumption that there are no within female differences in DEE within the egg laying sequence. We found a negative effect of temperature and a positive effect of female body mass on DEE but no evidence for differences in DEE between early and late laying females. However, costs incurred during egg laying may have carry-over effects later in the breeding cycle and if such carry-over effects differ for early and late laying females this could contribute to the maintenance of phenotypic variation in laying dates.     

The effect of replacing soya bean oil with glycerol in diets on performance,egg quality and egg fatty acid composition in laying hens

The objective of this experiment was to replace soya bean oil with glycerol in laying hen diets and assess the change’s effect on performance, parameters of egg quality and the egg fatty acid profile. A total of 60 44-week-old Hy-Line W36 laying hens were distributed according to a completely randomised experimental design into four treatments consisting of glycerol substitutions for soya bean oil dietary at varying inclusion levels (0%, 25%, 50% and 75%), with five replicates of three birds each. Dietary treatments had no significant effect on BW change, egg production, feed intake, feed conversion ratio, egg weight and egg mass of laying hens. The inclusion of glycerol in the diet of laying hens had no significant effect on egg specific gravity, eggshell breaking strength, eggshell weight, eggshell thickness, egg shape index, albumen index, yolk index, haugh unit, albumen pH, yolk pH and egg yolk colour values. The inclusion of glycerol in the diet of laying hens had no significant effect on palmitic, palmitoleic, stearic, oleic and linolenic acid contents of the egg yolk. The linoleic acid and polyunsaturated fatty acid contents of the egg yolk significantly decreased with the higher levels of dietary glycerol supplementation (P<0.05). The results of this study show that it is possible to replace 75% of soya bean oil (4.5% in diet) with glycerol.     

Intraclutch variation in avian eggshell pigmentation: the anaemia hypothesis

Many passerine species lay eggs that are speckled with dark protoporphyrin pigmentation. Because protoporphyrin is mainly derived from the blood, we here formulate and test a new hypothesis that links an increase in anaemia along the laying sequence to within-clutch variation in egg pigmentation. More intense pigmentation is expected if pigments accumulate during enhanced red blood cell production in response to anaemia. Reduced pigmentation is expected if pigments are derived from the degradation of red blood cells that circulate in smaller numbers due to blood loss. To test this hypothesis, we manipulated anaemia in great tit (Parus major) females by infesting the nests with hen fleas (Ceratophyllus gallinae) prior to egg laying. Polychromatophil (i.e., immature red blood cells) percentage, as a measure of blood cell production, was positively correlated with parasite load confirming that female great tits experienced stronger anaemia when infested with haematophagous parasites during egg laying. We found a positive relationship between spot darkness and laying order that weakened under high parasite load. This result suggests that anaemia in females due to blood-sucking parasites led to diminished protoporphyrin from disintegrated red blood cells and hence a decreased deposition of protoporphyrin. However, the overall increase in pigment darkness along the laying sequence suggests that pigments also accumulate by enhanced red blood cell production caused by anaemia due to egg production itself.     

Potential use of seaweeds in the laying hen ration to improve the quality of n-3 fatty acid enriched eggs

An association between dietary fish oil and decreased yolk weight and reduced sensory quality of eggs has been reported when eggs are enriched with n-3 FA from fish oil. Seaweeds are an important source of compounds that seem to increase egg weight when included in the laying hen diet. The objectives of this study were to determine the influence of the dietary seaweeds Macrocystis pyrifera, Sargassum sinicola and Enteromorpha sp. on the physical quality, lipid composition and consumer acceptability of n-3 FA enriched eggs. One-hundred and forty-four 35-week-old Leghorn hens were randomly distributed in four treatments that consisted of the inclusion of 2% of sardine oil (SO) and 10% of each marine alga (MA) in laying hens' diets; a control diet (C) was also prepared. The study lasted 8 weeks and egg physical quality, egg lipids and sensory attributes were evaluated. The results showed that incorporation of 10% M. pyrifera in the diets is an effective way of increasing the n-3 FA content, the albumen height and yolk color, but not the egg weight, when these are enriched with n-3 FA from fish oil. The egg flavor was also not affected.     

Egg size and offspring performance in the collared flycatcher (<Emphasis Type="Italic">Ficedula albicollis</Emphasis>): a within-clutch approach

Adaptive within-clutch allocation of resources by laying females is an important focus of evolutionary studies. However, the critical assumption of these studies, namely that within-clutch egg-size deviations affect offspring performance, has been properly tested only rarely. In this study, we investigated effects of within-clutch deviations in egg size on nestling survival, weight, fledgling condition, structural size and offspring recruitment to the breeding population in the collared flycatcher (Ficedula albicollis). Besides egg-size effects, we also followed effects of hatching asynchrony, laying sequence, offspring sex and paternity. There was no influence of egg size on nestling survival, tarsus length, condition or recruitment. Initially significant effect on nestling mass disappeared as nestlings approached fledging. Thus, there seems to be limited potential for a laying female to exploit within-clutch egg-size variation adaptively in the collared flycatcher, which agrees with the majority of earlier studies on other bird species. Instead, we suggest that within-clutch egg-size variation originates from the effects of proximate constraints on laying females. If true, adaptive explanations for within-clutch patterns in egg size should be invoked with caution.     

Quantitative genetic variation and selection of enzyme activities in Drosophila melanogaster

The nature of the genetic variation for the activity of three enzymes (α-GPD, ME, and SOD) was studied by means of analyses of variance among full-sib and half-sib families. The results presented here indicate that the genetic variation of activity of these enzymes consist primarily of non-additive genetic variance. A moderate level of additive genetic variation was found only for α-GPD activity. We also examined the question whether an association exists between enzyme activities and selection for preadult developmental time. Using the method developed by Lande and Arnold (1983), significant directional selection was observed for α-GPD activity.     

The lysozyme from insect (Manduca sexta) is a cold-adapted enzyme

Enzymatic activity is dependent on temperature, although some proteins have evolved to retain activity at low temperatures at the expense of stability. Cold adapted enzymes are present in a variety of organisms and there is ample interest in their structure-function relationships. Lysozyme (E.C. 3.2.1.17) is one of the most studied enzymes due to its antibacterial activity against Gram positive bacteria and is also a cold adapted protein. In this work the characterization of lysozyme from the insect Manduca sexta and its activity at low temperatures is presented. Both M. sexta lysozymes natural and recombinant showed a higher content of alpha-helix secondary structure compared to that of hen egg white lysozyme and a higher specific enzymatic activity in the range of 5-30 degrees C. These results together with measured thermodynamic activation parameters support the designation of M. sexta lysozyme as a cold adapted enzyme. Therefore, the insect recombinant lysozyme is feasible as a model for structure-function studies for cold-adapted proteins.     

Infradian rhythmicity in egg production features in relation to antioxidant profiles of Rhode Island Red (RIR) birds reared at backyard in different agroclimatic zones of West Bengal during summer stress

Egg production features viz. weekly hen day and egg weight together with some stress markers were studied in RIR birds reared under backyard in different agroclimatic zones of West Bengal. Overall, weekly hen day average and egg weight in summer was 3.39 ± 0.09 and 45.13 ± 0.24 g, respectively. But the pattern of egg production in various zones is not same, as significant egg production difference (P ≤ 0.01) among zones was noticed in summer, from 26th to 37th week. There was significant (P ≤ 0.01) correlation between weekly hen day average and egg weight on 26th, 35th and 37th week (P ≤ 0.05). The observed overall level of antioxidant enzymes viz. SOD (U/g of Hb), glutathione peroxidase (GSH-Px) (μmol/L), TAS (mmol/L) and LDH (IU/L) were 0.56 ± 0.61, 565.15 ± 0.61, 1.43 ± 0.61 and 203.05 ± 0.61, respectively, irrespective of zones. It was observed that mean concentration of SOD, GHS-Px, TAS and LDH of RIR birds reared at backyard have positive association with weekly hen day average and average egg weight throughout summer stress. The current findings showed that RIR birds reared at backyard had better adaptation ability to summer stress in different agroclimatic zones of West Bengal.     

Avian egg size: variation within species and inflexibility within individuals

Egg size is a widely-studied trait and yet the causes and consequences of variation in this trait remain poorly understood. Egg size varies greatly within many avian species, with the largest egg in a population generally being at least 50% bigger, and sometimes twice as large, as the smallest. Generally, approximately 70% of the variation in egg mass is due to variation between rather than within clutches, although there are some cases of extreme intra-clutch egg-size variation. Despite the large amount of variation in egg size between females, this trait is highly consistent within individuals between breeding attempts; the repeatability of egg size is generally above 0.6 and tends to be higher than that of clutch size or laying date. Heritability estimates also tend to be much higher for egg size (> 0.5) than for clutch size or laying date (< 0.5). As expected, given the high repeatability and heritability of egg size, supplemental food had no statistically significant effect on this trait in 18 out of 28 (64%) studies. Where dietary supplements do increase egg size, the effect is never more than 13% of the control values and is generally much less. Similarly, ambient temperature during egg formation generally explains less than 15% of the variation in egg size. In short, egg size appears to be a characteristic of individual females, and yet the traits of a female that determine egg size are not clear. Although egg size often increases with female age (17 out of 37 studies), the change in egg size is generally less than 10%. Female mass and size rarely explain more than 20% of the variation in egg size within species. A female's egg size is not consistently related to other aspects of reproductive performance such as clutch size, laying date, or the pair's ability to rear young. Physiological characteristics of the female (e.g. endogenous protein stores, oviduct mass, rate of protein uptake by ovarian follicles) show more promise as potential determinants of egg size. With regards to the consequences of egg-size variation for offspring fitness, egg size is often correlated with offspring mass and size within the first week after hatching, but the evidence for more long-lasting effects on chick growth and survival is equivocal. In other oviparous vertebrates, the magnitude of egg-size variation within populations is often as great or greater than that observed within avian populations. Although there are much fewer estimates of the repeatability of egg size in other taxa, the available evidence suggests that egg size may be more flexible within individuals. Furthermore, in non-avian species (particularly fish and turtles), it is more common for female mass or size to explain a substantial proportion of the variation in egg size. Further research into the physiological basis of egg-size variation is needed to shed light on both the proximate and ultimate causes of intraspecific variation in this trait in birds.