Predator-induced maternal effects determine adaptive antipredator behaviors via egg composition

In high-risk environments with frequent predator encounters, efficient antipredator behavior is key to survival. Parental effects are a powerful mechanism to prepare offspring for coping with such environments, yet clear evidence for adaptive parental effects on offspring antipredator behaviors is missing. Rapid escape reflexes, or “C-start reflexes,” are a key adaptation in fish and amphibians to escape predator strikes. We hypothesized that mothers living in high-risk environments might induce faster C-start reflexes in offspring by modifying egg composition. Here, we show that offspring of the cichlid fish Neolamprologus pulcher developed faster C-start reflexes and were more risk averse if their parents had been exposed to cues of their most dangerous natural predator during egg production. This effect was mediated by differences in egg composition. Eggs of predator-exposed mothers were heavier with higher net protein content, and the resulting offspring were heavier and had lower igf-1 gene expression than control offspring shortly after hatching. Thus, changes in egg composition can relay multiple putative pathways by which mothers can influence adaptive antipredator behaviors such as faster escape reflexes.

Maternal Age and Maternal Environment Affect Egg Composition, Yolk Testosterone, Offspring Growth and Behaviour in Laying Hens

Maternal effects have been reported to alter offspring phenotype in laying hens. In this study, we investigated the effects of maternal environment and maternal age on egg traits and offspring development and behaviour. For this, we ran two experiments. First (E1), commercial hybrid hens were reared either in aviary or barren brooding cages, then housed in aviary, conventional cages or furnished (enriched) cages, thus forming different maternal housing treatments. Hens from each treatment were inseminated at three ages, and measures of egg composition, yolk testosterone concentration and offspring’s development, anxiety and fearfulness were assessed. In experiment 2 (E2), maternal age effects on offspring's growth and behaviour were further investigated using fertile eggs from commercial breeder flocks at three ages. Results from E1 showed that maternal age affected the majority of measures including egg composition, yolk testosterone, offspring growth, anxiety and fearfulness. Maternal rearing and housing affected fewer measures but included egg characteristics, offspring weight and behaviour. Effects of maternal age were not replicated in E2, possibly due to higher tolerance to maternal effects in commercial breeders. Overall, our research confirms that maternal environment and maternal age affect the offspring of laying hens in a variety of ways. These effects may be mediated by the natural decrease in egg yolk testosterone concentration over time.

Effect Of Length Of Lay Of Nigeria Indigenous Chickens On Their Egg Composition And Shell Quality

Three hundred and thirty eggs collected from the second to the seventh month of production, from a flock of the Nigeria indigenous (NI) chickens, were analysed to determine the effect of the length of lay on egg composition and shell quality. The weights of the whole egg and its components as well as shell thickness were measured monthly while the proportion of the various components; egg shape index, shell density and shell weight per surface area were calculated. The results showed that egg weight, albumen weight and % albumen increased (P<0.05) with length of lay by 2.6g, 3.5g, 3.5g and 5.6% respectively between 2nd and 7th months. The change in the weight of the yolk, shell and egg shape index was not significant (P>0.05) between the 2nd and 7th months while % yolk, % shell, shell thickness and the shell weight per surface area decreased (P<0.05) by 4.2%, 0.64%, 0.04mm and 0.003g respectively within the same period. Strong phenotypic correlations were observed between the weights of the whole egg and the albumen (r=0.81), shell (r=0.63) and yolk (r=0.46) and also between shell thickness and its weight per surface area (r=0.81). These results indicate that egg size increased as the NI hen advanced in lay. Eggs laid in the 6th and 7th months contained more albumen than those laid earlier and the shell thickness decreased as the hens advanced in lay thus making them more liable to breakage.

Effect of Allium Extract Supplementation on Egg Quality, Productivity, and Intestinal Microbiota of Laying Hens

The use of allium extract containing propyl propane thiosulfonate (PTSO) as hen feed supplement was evaluated to demonstrate its positive effect on egg production and intestinal microbiota modulation. The study was carried out on 90 laying hens whose feed was supplemented with allium extract for 28 days. Nutritional properties of eggs were not affected, whereas an improvement in productivity was observed based on the increase weight of eggs. In addition, a modulator effect on intestinal microbiota was confirmed by the increase in Lactobacillus spp. and Bifidobacterium spp., as well as by the reduction in Enterobacteriaceae populations. Finally, the preservation of egg composition was checked by monitoring the content of PTSO, using a new analytical method consisting of the use of solid phase extraction and ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Consequently, based on current results, Allium spp. extract rich in organosulfur compounds such as PTSO added to the diet had a beneficial effect on the microbiota and would seem to be a possible alternative to increase productivity, while not affecting the biochemical composition of egg. However, further studies on the effects of allium extract as feed supplement are necessary.

The Golden Egg: Nutritional Value, Bioactivities, and Emerging Benefits for Human Health

Egg is an encapsulated source of macro and micronutrients that meet all requirements to support embryonic development until hatching. The perfect balance and diversity in its nutrients along with its high digestibility and its affordable price has put the egg in the spotlight as a basic food for humans. However, egg still has to face many years of nutritionist recommendations aiming at restricting egg consumption to limit cardiovascular diseases incidence. Most experimental, clinical, and epidemiologic studies concluded that there was no evidence of a correlation between dietary cholesterol brought by eggs and an increase in plasma total-cholesterol. Egg remains a food product of high nutritional quality for adults including elderly people and children and is extensively consumed worldwide. In parallel, there is compelling evidence that egg also contains many and still-unexplored bioactive compounds, which may be of high interest in preventing/curing diseases. This review will give an overview of (1) the main nutritional characteristics of chicken egg, (2) emerging data related to egg bioactive compounds, and (3) some factors affecting egg composition including a comparison of nutritional value between eggs from various domestic species.