We have explanted mouse blastocysts into culture dishes and studies the positioning of the inner cell mass (ICM) at the time of attachment in order to establish what effect the location of the inner cell mass has on the subsequent development of embryos in vitro. We show that blastocysts may attach to the substrate with any portion of the trophectoderm. The location of ICM within the attaching ...

Sexual selection has been identified as a major evolutionary force shaping male life history traits but its impact on female life history evolution is less clear. Here we examine the impact of sexual selection on three key female traits (body size, egg size and clutch size) in Galliform birds. Using comparative independent contrast analyses and directional discrete analyses, based on published ...

Predation of gypsy moth egg masses was studied in Slovakia from 1999 –2002. Predation on naturally laid egg masses was recorded and linear regression was used to test the hypothesis that predation follows a type II vs. type III functional response. We also investigated the role of egg mass predation in gypsy moth population dynamics. The relative contribution of invertebrates vs. vertebrates as...

During recent decades productivity of laying hens increased substantially (Elliot, 2008). Not only egg number, egg mass, and feed conversion has increased but also persistency of lay has improved. As such, this must have implications on the optimal amino acid nutrition of current laying hen strains. Simply stated, increasing egg mass output per hen means an increased amino acid output which has...

Mammalian fertilization requires sperm to penetrate the cumulus mass and egg zona pellucida prior to fusion with the egg. Although sperm penetration through these physical barriers is essential, the molecular mechanism has not yet been completely elucidated. In addition to sperm motility, hyaluronan-hydrolyzing and proteolytic enzymes of sperm have been suggested to participate in the penetrati...

lysozyme is one of the bioactive components of eggs with well known antibacterial potential, widely used in food industry, medicine and pharmaceutics. in this study, the possibility of quail’s egg lysozyme concentration and activity (modified via amino acids dietary supplementation) was investigated. in accordance with lysozyme amino acids profile, four amino acids of: asparagine, arginine, gly...

An experiment was conducted that examined the effect of day-to-day variability of dietary energy on feed intake behavior. Three levels of average daily dietary ME composition (2,580, 2,814, and 3,009 kcal/kg) and three levels of day-to-day variability of ME (low, medium, and high) were assigned to nine groups of DeKalb-XL laying hens in a 3x3 factorial design. Each of the nine treatments contai...

This experiment was conducted to investigate the effects of different levels of L-carnitine on productive performance, egg quality and blood parameters in laying hens. Forty-eight Hy-Line W-36 egg Layers were weighed at 90 weeks of age and randomly allocated into 16 cages (three hens per cage). Four dietary treatments were prepared by supplementing L-carnitine (0, 50, 100 and 150 mg/kg of diet)...

the objective of present study was to determine the effects of β-mannanase-based enzyme (hemicell®) on productive performance and egg quality in diets containing graded levels of whole date waste (wdw) fed to laying hens. a total of 336 hy-line leghorn hens after production peak were randomly divided into 56 cages. eight iso-energetic and iso-nitrogenous experimental diets in a 4 × 2 factorial ...

Life history trade-offs are often hierarchical with decisions at one level affecting lower level trade-offs. We investigated trade-off structure in female side-blotched lizards (Uta stansburiana), which exhibit two evolved strategies: yellow-throated females are K-strategists and orange-throated are r-strategists. Corticosterone treatment was predicted to differentially organize these females' ...