Egg mass shows large intraspecific variation in birds and yet the mechanisms underlying this variation remain unknown. We hypothesized that estradiol would play a central role in determining egg mass, since this hormone stimulates the production of yolk precursors (vitellogenin and very-low density lipoprotein, VLDL) by the liver, and of albumen by the oviduct. We gave European starlings (Sturn...

Phenotypic plasticity and phenotypic stability are major components of the adaptive evolution of organisms to environmental variation. The invariant two-egg clutch size of Eudyptes penguins has recently been proposed to be a unique example of a maladaptive phenotypic stability, while their egg mass is a plastic trait. We tested whether this phenotypic plasticity during reproduction might result...

This experiment was conducted to determine the effect of using L-threonine and reducing dietary levels of crude protein (CP) on egg production criteria in layers. Three hundred of Hy-Line W36 laying hens were used in this experiment. This experiment consisted of three experimental treatments with five replications in each. Experimental treatments included 3 diets with different levels of CP whi...

Objective: The experiment was conducted to evaluate the effect of different levels of germinated barley on performance and egg quality in laying hen. Methods: One hundred and twenty laying hens, 44-weeks old, Lohmann LSL hens were used in this experiment. Birds were assigned randomly to the groups, each of which consisted of 20 birds (4 replicate cages each containing 5 birds). The experiment w...

This study was conducted to evaluate the effect of different levels of sunflower meal (SFM) and niacin on laying hens performances, biochemical parameters, antioxidant status, and egg yolk cholesterol concentration. A total of 960, White Leghorn (Hy-Line W-36) commercial layers were randomly assigned to 12 groupsof 8 replicates with 10 hens each. Hens were allocated to diets 1 through 12 in a 3...

Species with "slow" life history strategies (long life, low fecundity) are thought to produce high-quality offspring by investing in larger, but fewer, young. Larger eggs are indeed associated with fewer eggs across taxa and can yield higher-quality offspring. Tropical passerines appear to follow theory because they commonly exhibit slow life history strategies and produce larger, but fewer, eg...

this study was conducted to determine the nutritional value of seaweed gracilariopsis persica and to evaluate its utilization in layer nutrition. metabolizable energy and chemical composition of seaweed were measured. 100 hy-line w-36 hens were allocated to five dietary groups with five treatment group (experimental diets containing zero, five, 10, 15 and 20 percent seaweed) and it lasted for 1...

two fungal species glomus mosseae and glomus intraradices as well as meloidogyne javanica nematode were used in order to evaluate the effects of arbuscular mycorrhizal fungi on control of different populations of root-knot nematode in tomato. a greenhouse test was established as factorial experiment based on completely randomized design with 8 treatments and 4 replicates followed by mycorrhizal...

We examined whether the previously reported low cost of embryonic development in pelicans could be attributed to a more efficient conversion of egg energy to hatchling tissues as a result of high initial egg water content, low embryonic metabolic rate and growth later in incubation than in more precocious species. We therefore determined egg and hatchling composition and the development of embr...