The entomopathogenic nematode (EPN), Steinernema yirgalemense, is an effective biological control agent against a variety of important insect pests in South Africa. To develop a South African EPN product feasibly in South Africa, EPNs need to be mass-produced. This study aimed to record the population dynamics of S. yirgalemense with in vitro liquid production in shake flasks, with a protein source of powdered egg yolk. The Erlenmeyer flask results indicated variation between flasks, albeit still achieving high yields. The reasons for attaining such variability in the recovery, yield, and growth stages are unclear, hence requiring further studies seeking to increase consistency. The results obtained indicate that, when IJ recovery is low, yields are also low due to relatively few reproductive adults being present in solution, which, in turn, produces more offspring, which later converts to the desired infective juvenile used for product formulation development. For commercial viability, a consistent production system is required that produces predictable yields. This study showed comparable high yields achieved with the flasks and in an early-stage bioreactor setup, being a positive development for S. yirgalemense mass production. Prior to the bioreactor scale-up process, protocol of mass production, the population and growth dynamics of the nematodes in the flask environment requires understanding. This is a positive step, leading to the future commercialisation of a local EPN product.

The aim of this study was to compare different concentrations of soy lecithin (LEC0.01%, LEC0.05% and LEC0.1%) with egg yolk (Control) in cooling extenders during the storage of semen at 5ºC for 5 days. Twelve dogs (n = 12) were selected, and semen was cooled and assessed after 2, 24, 48, 72, 96 or 120 h. At each time point, sperm were analyzed for kinetic patterns (using computer-assisted sperm analysis), mitochondrial activity (3′3- diaminobenzidine assay), lipid peroxidation (TBARS assay), DNA fragmentation (SCSA®) and plasma and acrosome membrane integrity (eosin/nigrosin and fast green/rose Bengal stains, respectively). The Control group (1814.4 ± 197.2) presented the highest rates of lipid peroxidation at 120 h. Conversely, progressive motility (42.8 ± 4%), linearity (45.4 ± 1%), and VAP (88 ± 3%) were higher in the Control group. In addition, there was lower mitochondrial activity in the Control group at 72 h. Therefore, our data show that lecithin used at these concentrations was not able to maintain sperm viability at as high qualities as would egg yolk. Moreover, the decrease in high mitochondrial activity and the persistence of sperm motility may indicate a compensatory mechanism in canine spermatozoa (i.e., glycolytic pathway). Furthermore, these higher lipid peroxidation indexes could indicate the necessity for future therapy using extenders and antioxidants over a long cooling time for dog sperm.

One of the environmental challenges that the poultry industry has faced is manure utilisation and/or disposal. Poultry manure and its nitrogenous compounds can be a potential pollutant causing eutrophication, nitrate or nitrite contamination of water, ammonia volatilisation, and acid deposition in the air. Therefore, reducing nitrogen excretion and emissions in poultry manure is important to maintain a clean environment. Proper nutrition is an important first step to optimise performance and growth in animals as well as to reduce the negative impacts on the environment. Amino acids are components of protein nutrition that greatly influence animal growth. However, excess or insufficient amino acid supplementation in diets increases nitrogen excretion and emissions. One way to reduce this is to prevent uricase activity in the microflora in poultry manure. Egg yolk antibodies are economic alternatives for administering in feed to poultry. Supplementation of feed grade antibodies into poultry diets can be a potential approach to minimise bacterial uricase activity and reduce ammonia emissions from poultry manure. In order to use this dietary strategy effectively, a well-balanced feed formulation and a more practical way of delivering the antibodies in feeds remains to be developed.

The chicken egg and foods containing egg components are an important part of human nutrition. Furthermore, eggs are a potential source of bioactive molecules and a potential delivery system for therapeutic proteins, explaining the continuing scientific interest in eggs and their components. Using mass spectrometry-based high-throughput proteomic techniques, 119 proteins in egg yolk, 78 proteins in egg white, and 528 proteins in the decalcified eggshell organic matrix have recently been identified. Most of these proteins were identified in their respective egg compartment for the first time. Some of these proteins were already known from chicken tissues or other egg compartments, but many were novel. In the eggshell soluble matrix 39 phosphoproteins containing more than 150 different phosphorylation sites were identified. Twenty-two of the identified phosphoproteins had not been recognized as phosphoproteins previously.

During the past four decades, research efforts directed toward reducing shell egg cholesterol content have centred on genetic selection or alteration of the laying hens' diet with various nutrients, natural products, non-nutritive factors, or pharmacological agents. However, the vast majority of these experimental approaches elicited only minimal changes (<10%) at best or, as in the case of dietary azasterols and triparanol, resulted in the unacceptable replacement of yolk cholesterol by desmosterol. In contrast, when 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (‘statins’), garlic paste, or pharmacological amounts of copper were orally administered to chickens, yolk cholesterol levels were reduced by up to 46%, 32%, or 34%, respectively. The previous paper in this two-part series provided a justification for low-cholesterol egg production and reviewed cholesterol metabolism in the laying hen, avian embryonic cholesterol needs, and genetic and nutritional approaches to chicken egg cholesterol reduction. The present paper provides a comprehensive overview of the use of non-nutritive dietary factors and select pharmacological compounds as egg cholesterol-lowering agents, and discusses emerging strategies for lowering the cholesterol content of shell eggs. With the recent advances in avian genomics and transgenesis, it is anticipated that the greatest advances in the area of yolk cholesterol reduction will be attained through manipulation of key genes whose protein products mediate intestinal sterol absorption, hepatic cholesterol and lipoprotein synthesis, and/or lipoprotein uptake by growing oocytes. However, the future commercial availability of low-cholesterol eggs produced by transgenic hens ultimately will be influenced by the nature of the regulatory environment for bioengineered foods, public acceptance, and economics.

In laying hens, cholesterol is primarily biosynthesized in the liver and incorporated into vitellogenin (VTG) and triglyceride-rich very low density lipoprotein (VLDL) particles, which are secreted into the bloodstream and subsequently taken up by growing oocytes via receptor-mediated endocytosis. VLDL and VTG are then intracellularly transformed into yolk, constituting ∼60% and 24% of yolk dry matter and ∼95% and 5% of yolk cholesterol, respectively. During the past four decades, research efforts directed toward reducing shell egg cholesterol content have centred on genetic selection or alteration of the laying hens’ diet with various nutrients, natural products, non-nutritive factors, or pharmacological agents. The present paper will provide a justification for low-cholesterol egg production, primarily in the context of the heterogeneity of response to dietary cholesterol in humans, and will review cholesterol metabolism in the laying hen, avian embryonic cholesterol needs, and genetic and nutritional approaches to chicken egg cholesterol reduction. A subsequent paper will provide a comprehensive overview of the use of non-nutritive dietary factors and select pharmaceuticals as egg cholesterol-lowering agents, and will discuss emerging strategies for lowering the cholesterol content of shell eggs.

Differences in structure between egg constituent proteins influence their ability to interact, upon heating, in gel systems or to compete for space at the interface of oil droplets in oil/water (o/w) emulsions. Phase separation phenomena could be the rule in protein network systems where mixtures of egg yolk with egg white or other protein containing materials are employed. In emulsions, apolipoproteins of LDL micelles appear to play a dominant role in adsorption and interfacial membrane formation around the oil droplets. Yolk granular proteins also have the ability to contribute in the building of the adsorbed layer although their adsorption and stabilizing potential seem to depend on factors as such as NaCl content and pH and also on the extent of granular structure disorganization. Egg white and milk whey proteins are competitively displaced from emulsion oil interfaces by yolk lipoproteins due to the globular and rigid structure of the former. Casein proteins also appear to adsorb less effectively in the presence of yolk apolipoproteins in spite of their rather disorganized molecular structure.

The aim of this review is to consider the potential mechanisms birds may use to manipulate the sex of their progeny, and the possible role played by maternal hormones. Over the past few years there has been a surge of reports documenting the ability of birds to overcome the rigid process of chromosomal sex determination. However, while many of these studies leave us in little doubt that mechanisms allowing birds to achieve this feat do exist, we are only left with tantalizing suggestions as to what the precise mechanism or mechanisms may be. The quest to elucidate them is made no easier by the fact that a variety of environmental conditions have been invoked in relation to sex manipulation, and there is no reason to assume that any particular mechanism is conserved among the vast diversity of species that can achieve it. In fact, a number of intriguing proposals have been put forward. We begin by briefly reviewing some of the most recent examples of this phenomenon before highlighting some of the more plausible mechanisms, drawing on recent work from a variety of taxa. In birds, females are the heterogametic sex and so non-Mendelian segregation of the sex chromosomes could conceivably be under maternal control. Another suggestion is that follicles that ultimately give rise to males and females grow at different rates. Alternatively, the female might selectively abort embryos or ‘dump lay’ eggs of a particular sex, deny certain ova a chance of ovulation, fertilization or zygote formation, or selectively provision eggs so that there is sex-specific embryonic mortality. The ideas outlined in this review provide good starting points for testing the hypotheses both experimentally (behaviourally and physiologically) and theoretically.

Hen egg proteins are desirable ingredients of many foods. Today, eggs are widely distributed in international trade and the egg industry is an important segment of the world food industry. Hen egg proteins have unique functional properties such as gelling, foaming (egg white) and emulsifying (egg yolk) properties. This review describes the recent advances in molecular basis of the development of these functional properties as well as technical development of new approaches for improving the functional properties of egg proteins. A better understanding of structure-function relationship of egg protein functionality in food system will enable us for tailoring food protein for specific uses.

Drug and pesticide residues in edible poultry tissues and eggs are a human food safety concern. Quantifying and predicting the concentrations of residues in eggs is a particular challenge because of the unique aspects of egg development and compartmentalisation of the yolk and white. For a number of years, research efforts have been directed at examining residue incorporation nto eggs and developing models to predict residue incursion. This paper will review the physiology of egg yolk formation as it relates to residue incursion, the models developed to understand and quantify residue patterns, and the use of magnetic resonance imaging to detect residue incorporation into eggs.

The egg yolk contains several substances of potential therapeutic value, some of which are already used in commercial products. A number of scientific papers dealing with their properties and applications have been published. In this review we present some current and possible applications for egg yolk lipids, lipoprotein, phosvitin, sialic acid and antibodies (IgY). Moreover, we discuss the possibilities of increasing the yield of yolk and simultaneously the yield of these substances by both management and breeding approaches.

Egg-yolk protein hydrolysate (YPp) is an alternative protein source in formulas for infants with intolerance to cow's milk or soyabean protein, or for patients with intestinal disorders. However, the nutritional value of YPp has never been investigated. YPp was prepared by enzymic hydrolysis of delipidated yolk protein, which led to an average peptide length of 2.6 residues. Three experiments were performed. In Expt 1, we compared the intestinal absorption rate of YPp and soyabean protein hydrolysate (SPp) in rats. YPp and SPp solutions were injected into the duodenum of anaesthetized rats and blood samples were taken from the portal vein at 7, 15, 30, 60, and 120 min. A higher amino acid concentration in the serum of the YPp group demonstrated that YPp was absorbed faster than SPp. In Expt 2, the effects of dietary YPp and SPp on body-weight gain, protein efficiency ratio (PER) and feed efficiency ratio (FER) were determined. At the end of the experiment, body weight had increased in both groups, while PER and FER were significantly higher in rats fed on YPp. In Expt 3, to investigate the effects of dietary YPp and SPp on N metabolism, we determined the biological value and net protein utilization. Yolk protein was the reference protein. Biological value and net protein utilization values were very similar between animals fed on yolk protein and YPp diets, and significantly higher than in rats fed on the SPp diet. The present findings demonstrate that there is no adverse effect of hydrolysis of yolk protein on N utilization, and that the nutritive value of YPp is similar to that of yolk protein and superior to that of SPp.

Dietary flax seed may prove to be a key feed ingredient in establishing the egg as a food useful for promoting cardiovascular health in humans. Yolk linolenic acid (LNA; 18:3n−3) increases in a linear fashion in response to graded levels of ground flax seed and whole flax seed if grit is provided in the feed to promote in vivo seed grinding. In contrast, the metabolic derivatives of LNA, eicosapentaenoic acid (EPA; 20:5n−3) and docosahexaenoic acid (DHA; 22:6n−3), are deposited only in limited amounts regardless of the level or form of flax seed fed. The distribution of the omega-3 polyunsaturated fatty acids (n−3 PUFA) in egg yolk lipid classes varies between laying stocks and these differences appear to influence the oxidative and sensory qualities of the product. Dietary flax seed results in apparently benign fluctuations in body weight of mature laying hens. Undesirable changes in egg production have only been reported for young birds early in their reproductive cycles. Changes in egg quality include reduced shell weight and decreased yolk weight. It is proposed that yolk weight reduction is related to changes in circulating oestradiol brought about by either n−3 PUFA or the phyto-oestrogens characteristic of flax seed.

Amine-organic buffers (BESKOH and TESTRIS) were compared for their ability to be used for buck semen dilution in a freezing procedure. BESKOH showed better results (P < 0·05) at the time of dilution and after chilling at +5°C (72% motility v. 54% at dilution and 62% v. 39% after chilling). After freezing and thawing, none of the variables measured (motility, normal acrosome ridge and normal swelling) was significantly different. A washing procedure was necessary when freezing was undertaken and egg yolk addition was necessary to avoid cold shock as the temperature lowered during chilling. There were no significant differences between a 3% and 12% level of egg yolk addition.