Avian eggs contain a variety of maternally-derived substances that can influence the development and performance of offspring. The levels of these egg compounds vary in relation to environmental and genetic factors, but little is known about whether there are correlative links between maternal substances in the egg underlying common and different pathways of maternal effects. In the present study, we investigated genetically determined variability and mutually adjusted deposition of sex hormones (testosterone-T, androstenedione-A4 and progesterone-P4), antibodies (IgY) and antimicrobial proteins (lysozyme) in eggs of Japanese quail (Coturnix japonica). We used different genetic lines that were independently selected for yolk T concentrations, duration of tonic immobility and social reinstatement behaviour, since both selections for behavioural traits (fearfulness and social motivation, respectively) produced considerable correlative responses in yolk androgen levels. A higher selection potential was found for increased rather than decreased yolk T concentrations, suggesting that there is a physiological minimum in egg T levels. Line differences in yolk IgY concentrations were manifested within each selection experiment, but no consistent inter-line pattern between yolk IgY and T was revealed. On the other hand, a consistent inverse inter-line pattern was recorded between yolk IgY and P4 in both selections for behavioural traits. In addition, selections for contrasting fearfulness and social motivation were associated with changes in albumen lysozyme concentrations and an inverse inter-line pattern between the deposition of yolk IgY and albumen lysozyme was found in lines selected for the level of social motivation. Thus, our results demonstrate genetically-driven changes in deposition of yolk T, P4, antibodies and albumen lysozyme in the egg. This genetic variability can partially explain mutually adjusted maternal deposition of sex hormones and immune-competent molecules but the inconsistent pattern of inter-line differences across all selections indicates that there are other underlying mechanisms, which require further studies.
SUMMARYThe effects of maternal androgens on fitness-related traits of offspring are generally assumed to be epigenetic adaptations to the environment that may be encountered by the next generation. Possible constraints of high yolk androgen transfer are still not understood, although a suppressed immune response in offspring is frequently considered. The aim of our study was to examine the innate immune defence in high (HET) and low egg testosterone (LET) lines of Japanese quail, which differ in the hormonal milieu of their eggs, thus providing a good physiological model for the study of androgen-mediated maternal effects. Acute phase response was induced by a lipopolysaccharide injection in 12-day-old quail and plasma corticosterone and the heterophil:lymphocyte ratio were measured at 1 and 3h post-treatment. Basal levels of non-specific antibodies (IgY) were determined in the circulation. We found that HET quail were heavier than LET quail from the second week of age, indicating enhanced post-hatching growth. At 1h post-lipopolysaccharide challenge, plasma corticosterone concentrations increased in the HET but not in the LET line. The heterophil:lymphocyte ratio rose in both lines at 3h post-immune challenge, with a more pronounced response in HET quail. Moreover, HET chicks displayed higher IgY levels than LET chicks, suggesting either enhanced passive immunoprotection or stimulated endogenous antibody production. In conclusion, our data demonstrate that the genetic selection for high egg testosterone content positively influences growth and, simultaneously, does not limit the acute phase response in young quail.
Lighting conditions during incubation can influence embryonic development, post-hatching ontogeny and production efficiency. Previous studies revealed that different light colours differently affect pineal melatonin biosynthesis in embryos and postembryonic development of broiler chickens, but physiological mechanisms mediating these effects are not known. Cold and warm white light consists of different wavelengths and therefore the aim of the present study was to explore if these two lights can differently influence the development of circadian melatonin biosynthesis, production of thyroid hormones and corticosterone, concentration of metabolites (glucose, cholesterol and triacylglycerols) as well as expression of two important immune genes, presenilin 1 and avian beta-defensin 1 (AvBD-1). We evaluated these traits in embryos before hatching (456, 460, 465, 468 and 472 h of incubation) and in hatchlings. The rhythmic profile of pineal melatonin with higher concentrations during the dark time was determined in both treatment groups. Melatonin levels increased considerably in hatchlings in comparison with embryos, but we found no difference in rhythm characteristics between groups. We did not identify any daily rhythms in plasma corticosterone and thyroid hormone levels in either studied age and no differences were found between light treatments in concentrations of thyroid hormones, corticosterone, metabolites and expression of presenilin and AvBD-1. The expected developmental increase of thyroid hormones was proved. Gene expression of presenilin increased in the duodenum of hatchlings in comparison with embryos, but the expression did not change in the bursa of Fabricius. On the other hand, expression of AvBD-1 decreased in hatchlings compared to embryos in both tissues. Based on these results, we can conclude that the colour temperature of white light did not influence endocrine and immune parameters determined in this study and probably monochromatic rather than polychromatic light should be used to influence embryonic development and postembryonic ontogeny of broiler chickens.
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