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Background: Chicken embryos emerge from their shell by the piercing movement of the hatching muscle. Although considered a key player during hatching, with activity that imposes a substantial metabolic demand, data are still limited. The study provides a bioenergetic and transcriptomic analyses during the pre-post-hatching period. Methods: Weight and morphology alongside content determination of creatine and glycogen were analysed. Transcriptome identified differentially expressed genes and enriched biological processes associated with hatching muscle development, catabolism, and energy provision. Using gene set enrichment, we followed the dynamics of gene-sets involved in energy pathways of oxidative phosphorylation, protein catabolism, glycolysis/gluconeogenesis, and glycogen metabolism. Results: Results show several significant findings: (A) Creatine plays a crucial role in the energy metabolism of the hatching muscle, with its concentration remaining stable while glycogen concentration is depleted at hatch and placement. (B) The hatching muscle has the capacity for de-novo creatine synthesis, as indicated by the expression of related genes (AGAT, GAMT). (C) Transcriptome provided insights into genes related to energy pathways under conditions of pre-hatch oxygen and post-hatch glucose limitations (oxidative phosphorylation: NDUF, MT-ND, SDH, UQCR, COX, MT-CO, ATP5, MT-ATP; glycolysis/gluconeogenesis: FBP,G6PC, PFKM; glycogen metabolism: PPP1, PYGL, GYG1). (D) The post-hatch upregulation of protein catabolic processes genes (PSMA, RNF, UBE, FBX), which align with the muscle's weight dynamics, indicates a functional shift from movement during hatching to lifting the head during feeding. Conclusions: There is a dynamic metabolic switch in the hatching muscle during embryo-to-hatchling transition. When glycogen concentration depletes, energy supply is maintained by creatine and its de-novo synthesis. Understanding the hatching muscle's energy dynamics is crucial, for reducing hatching failures in endangered avian species, and in domesticated chickens. [ABSTRACT FROM AUTHOR]

This experiment was carried out at hatcheries and laboratories of Animal Production Department - College of Agricultural Sciences - University of Sulaymaniyah, by using 240 fertilized egg (Ross 308), distributed to four treatments,T1= first treatment control treatment without hearing any sound, T2= second treatment hearing the hen call , T3= treatment third hearing chicks hatched call and T4= treatment fourth hearing chick with hen call, each treatment divided to three replicates and each repeater 20 eggs, hearing the sound from the age of 5 days form incubation and until the day of hatching, the sound was given for a period of 15 minutes per hour in 24 hours, the results showing: significantly (P≤0.01) improvement in embryonic development traits for all experimental treatments in embryonic test second and third compared with the control treatment, significantly (P≤0.01) improvement in the quality specifications for the hatching muscle and histological test for all experimental treatments compared with control treatment. [ABSTRACT FROM AUTHOR]

One of the most obvious adaptations to the brood parasitic mode of reproduction is the formation of eggs with unusually strong shells, which apparently reduce chances of egg breakage during laying and puncture ejection attempts of parasitic eggs by the hosts. We tested a hypothesis that strong eggshells of the Common Cuckoo, Cuculus canorus, may have also led to a stronger hatching muscle, musculus complexus. First, the Cuckoo hatching muscle had a higher density of fibers than that of the similarly sized Great Reed Warbler Acrocephalus arundinaceus chicks; and second, the cross-sectional area of fibers of the hatching muscle was smaller in the Cuckoo than in the Great Reed Warbler. We propose that the increased density of muscle fibers in the Cuckoo facilitates hatching out of structurally strong eggshells because chicks possessing this trait should be able to exert greater pressure on the shell during the hatching process. Our results are consistent with the hypothesis that the higher density of fibers in the musculus complexus represents another adaptation facilitating hatching from unusually strong parasitic eggs that has presumably evolved during coevolution involving the Cuckoo and its hosts. [ABSTRACT FROM AUTHOR]

Growth performance and meat yield of commercial broilers and turkeys has improved linearly each year during the past four decades (Havenstein et al., 2003b; Havenstein et al., 2003a; Havenstein et al., 2007), and this trend is likely to continue in the future as new technologies in genetics, biotechnology and developmental biology are adopted by the poultry industry. As the time it takes meat birds to achieve market size decreases, the period of embryonic development becomes a greater proportion of a bird's productive life. Therefore, incubation and embryonic development towards hatch is of greater relative importance to the successful rearing of meat poultry than ever before (Hulet 2007; Foye et al., 2007b). Consequently, anything that supports or limits growth and development during the incubation period will have a marked effect on overall growth performance and health of modern strains of meat poultry. Many poultry researchers now realize that future gains in genetic and production potential of poultry will come from advancements made during the incubation period and embryogenesis (Elibol et al., 2002; Peebles et al., 2005; Christensen et al., 2007; Collin et al., 2007; Leksrisompong et al., 2007). The urgent need to explore and understand the biology of incubation has been emphasised by several symposia: two held at the annual conference of the U.S. Poultry Science Society (July 2006-Edmonton, Alberta, Canada “Managing the embryo for performance”, and July 2007-San Antonio, TX Informal Nutrition Meeting “The impact of imprinting on biological and economical performance in animals”), and one held by the European Federation of World Poultry Science Society (October 2007-Berlin, Germany “Fundamental physiology and perinatal development in poultry), which were specifically devoted to demonstrating the importance of the embryonic period on poultry performance. This review will summarise the metabolic events and pathways in four of the most active tissues of embryos during the period just prior to hatch, and the hormonal control that coordinates the marked changes as the embryo prepares for its post-hatch life. [ABSTRACT FROM PUBLISHER]