Whether androgen deposition in eggs is physiologically costly for female birds has remained a crucial but unsolved question, despite a broad use of this assumption in functional studies. We tested whether females depositing high androgen concentrations experienced higher mass losses than females depositing low androgen concentrations. Analysing female body mass change during egg formation in ro...

The substitution effect of noug (Guzoitia abyssinica) seed cake with samma (Urtica simensis) leaf meal (SLM) was investigated on egg production and egg quality parameters in commercial layer hens. Five treatment (T) diets were formulated to contain SLM at 0% (T1), 3% (T2), 6% (T3), 9% (T4) and 12% (T5) by substituting noug seed cake. One-hundred fifty Isa Brown layer pullets w...

1. We used published data to investigate the combined influence of egg size and incubation temperature on embryonic development time for a broad assortment of aquatic insects at four different incubation temperatures (10, 15, 20 and 25 °C). 2. Embryonic development time (EDT) was positively correlated with egg size at each of the four temperatures, but with different relationships for univoltin...

In many organisms, large offspring have improved fitness over small offspring, and thus their size is under strong selection. However, due to a trade-off between offspring size and number, females producing larger offspring necessarily must produce fewer unless the total amount of reproductive effort is unlimited. Because differential gene expression among environments may affect genetic covari...

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...

It is necessary to distinguish new and old gypsy moth, Lymantria dispar (L.), egg masses when conducting gypsy moth population surveys. Egg masses within reach from the ground are touched to determine if they contain unhatched eggs and thus are considered new. The following 2 methods are used for egg masses not within reach: (1) visual discrimination between new and old egg masses or (2) by cal...

Egg production in oviparous vertebrates is assumed to be costly but the physiological basis of any costs remains unknown. The avian oviduct is a highly differentiated linear organ, with five functionally specific regions. Here we show that the oviduct regresses rapidly "from the top down" as soon as the more proximal regions have completed their function but while the distal regions still retai...

Rhizocephala, a group of parasitic castrators of other crustaceans, shows remarkable morphological adaptations to their lifestyle. The adult female parasite consists of a body that can be differentiated into two distinct regions: a sac-like structure containing the reproductive organs (the externa), and a trophic, root like system situated inside the hosts body (the interna). Parasitism results...

Rejection of the parasitic egg is the most important defence of hosts against brood parasites. However, this response is variable among and within species, and egg discrimination is not always followed by egg rejection. Low risk of parasitism and high risk of rejection costs may lead to the acceptance of the parasitic egg even if it has been previously recognized. The main aim of this paper is ...