Elevated corticosterone before hatch disrupts bone development in Japanese quail.

Galliformes are precocial with well-developed bones before hatch. Adverse early life experiences can have detrimental effects on growth and development, and in commercial settings overcrowding of breeding poultry is both commonplace and stressful. Stressed hens deposit higher levels of the stress hormone corticosterone in the yolk of their eggs, and this increases corticosterone levels in hatched chicks (Hayward & Wingfield, 2004). The effect of elevated pre-natal corticosterone on the skeletal system is unknown for birds but in mammals, adverse conditions before birth can have detrimental effects on bone length (Dancause et al, 2012), and exposure to corticosterone after hatch can impact on bone growth and reduce bone density in chickens (Luo, et al 2013). To investigate the effects of pre-natal corticosterone on bone development, we injected a physiologically relevant dose of the hormone into Japanese quail eggs at embryonic day 8 (8.5 ng, dissolved in peanut oil; n=31) and collected tibiotarsus at day 16. Control eggs were injected with peanut oil alone (n=35). Animal care and use protocols were carried out under the UK Home Office licence guidelines [Animal Scientific Procedures Act (1986)]. Our data shows that pre-natal elevation of corticosterone significantly reduces bone weight and bone strength (p < .05). Although studies in mammals have found sex differences in effects of stress on bone (Dancause et al, 2012), we did not observe sex differences for any bone properties measured. Further studies to investigate the effects of elevating corticosterone before hatch on bone later in life are ongoing, as well as analyses of density and histology in the embryonic samples. Our findings have implications for the welfare of birds housed in commercial barn systems where there is a problem of bone fragility due to the increased risk of collision and breakage of bones. Research supported by the BBSRC and World’s Poultry Science Association. Key words: Corticosterone, pre-natal, Japanese quail, bone, embryo. References: Hayward, L. S., & Wingfield, J. C. (2004). Maternal corticosterone is transferred to avian yolk and may alter offspring growth and adult phenotype. General and comparative endocrinology, 135(3), 365-371.