Effect of egg composition and oxidoreductase on adaptation of Tibetan chicken to high altitude

Abstract

Tibetan chickens have good adaptation to hypoxic conditions, which can be reflected by higher hatchability than lowland breeds when incubated at high altitude. The objective of this trial was to study changes in egg composition and metabolism with regards the adaptation of Tibetan chickens to high altitude. We measured the dry weight of chicken embryos, egg yolk, and egg albumen, and the activity of lactate dehydrogenase (LDH) and succinic dehydrogenase (SDH) in breast muscle, heart, and liver from embryos of Tibetan chicken and Dwarf chicken (lowland breed) incubated at high (2,900 m) and low (100 m) altitude. We found that growth of chicken embryos was restricted at high altitude, especially for Dwarf chicken embryos. In Tibetan chicken, the egg weight was lighter, but the dry weight of egg yolk was heavier than that of Dwarf chicken. The LDH activities of the three tissues from the high altitude groups were respectively higher than those of the lowland groups from d 15 to hatching, except for breast muscle of Tibetan chicken embryos on d 15. In addition, under the high altitude environment, the heart tissue from Tibetan chicken had lower LDH activity than that from Dwarf chicken at d 15 and 18. The lactic acid content of blood from Tibetan chicken embryos was lower than that of Dwarf chicken at d 12 and 15 of incubation at high altitude. There was no difference in SDH activity in the three tissues between the high altitude groups and the lowland groups except in three tissues of hatchlings and at d 15 of incubation in breast muscle, nor between the two breeds at high altitude except in the heart of hatchlings. Consequently, the adaptation of Tibetan chicken to high altitude may be associated with higher quantities of yolk in the egg and a low metabolic oxygen demand in tissue, which illuminate the reasons that the Tibetan chicken have higher hatchability with lower oxygen transport ability.

High altitude hypoxia as a factor that promotes tibial growth plate development in broiler chickens

“…Hypoxia refers to low partial pressure of oxygen (O 2 ) in the inspired air and threatens the survival, development, and reproduction of both humans and animals [ 3 – 10 ] because of its physiological challenges on the body. Jia et al .…”

“…Jia et al . [ 10 ] have revealed the unique physiological responses and adaptation mechanism of animals in response to high altitude hypoxia. Chickens provide a proper model to study physiological adaptations under hypoxic stress conditions, and TBCs are a unique aboriginal breed that has undergone selection for such trials to inhabit the high altitude Tibetan plateau.…”

Genome methylation and regulatory functions for hypoxic adaptation in Tibetan chicken embryos

“…The increased hatchability of the Tibetan chicken compared with lowland breeds under hypoxia, even for individuals that have migrated to and remained at lower altitudes for several years, shows the stable genetic mechanism underlying hypoxic adaptation ( Zhang et al, 2008a ). Tibetan chicken embryos have the physical foundations for hypoxic adaptation, including hatchability, mitochondrial respiratory function, embryonic organ system development, and oxidoreductase ( Bao et al, 2007 ; Jia et al, 2016 ; Zhang & Burggren, 2012 ; Zhang et al, 2008a ). Furthermore, genome variation analysis has identified a series of pathways and genes related to hypoxia in the Tibetan chicken ( Wang et al, 2015a ; Zhang et al, 2016 ).…”

Pectoral muscle transcriptome analyses reveal high-altitude adaptations in Tibetan chickens

“…Recent studies have explored the molecular mechanisms underlying various aspects of the adaptations of TCs to hypoxia. These have revealed physiological differences in TC embryos lower lactate dehydrogenase activity in the heart (Jia et al, 2016), lower water loss (Zhang et al, 2008) and lower complex I activity in the brain (Bao et al, 2007) than lowland chicken embryos incubated under hypoxic conditions. Several studies have also linked single-gene variations to the high-altitude adaptations of TCs.…”