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Acclimation to Heat During Incubation. 2. Embryo Composition and Residual Egg Yolk Sac Fatty Acid Profiles in Chicks

S. Yalçin^*,1, N. Badatliolu, V. Bruggeman, E. Babacanolu^*, . Uysal, J. Buyse, E. Decuypere and P. B. Siegel^#

^* Ege University, Faculty of Agriculture, Department of Animal Science, 35100 Izmir, Turkey; Celal Bayar University, Engineering Department, 45140 Manisa, Turkey; Laboratory for Physiology, Immunology, and Genetics of Domestic Animals, Department of Biosystems, Katholieke Universiteit Leuven, Kasteelpark Arenberg 30, 3001 Leuven, Belgium; Institute of Technology, Food Engineering Department, 35430 zmir, Turkey; and ^# Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061

¹ Corresponding author: servet.yalcin{at}ege.edu.tr

The aim of the research was to evaluate embryo composition and changes in egg yolk fatty acid composition during embryonic development as a function of incubation temperature and age of breeders. Eggs obtained from a common breeder stock at 3 ages: 32 (younger), 42 (mid age), and 65 (older) wk were divided into 2 groups and placed into 2 incubators: the control and the second where eggs were heat-acclimated (HA) at 38.5°C for 6 h daily from d 10 to 18 of incubation. Body composition of embryos and chicks were measured on d 14, 18, and at hatch, respectively. Fatty acid profiles of yolk and residual egg yolk sac of chicks were analyzed before incubation and at hatch, respectively. Moisture content of embryos was highest on d 14 and then decreased regardless of parental age and incubation temperature. Moisture content of chicks at hatch from 42- and 65-wk parents were lower than those of chicks from 32-wk parents, whereas the trend in chick fat content was opposite. Incubation temperature had no effect on composition of chicks. Consistently lower cis-4,7,10,13,16,19-eicosapentaenoic (docosahexaenoic acid, DHA; 22:6n-3) and cis-11,14,17-eicosatrienoic (20:3n-3) fatty acids in the residual yolk sac of chicks than in egg yolks before incubation may have resulted from preferential uptake from the yolk. The DHA content in the residual yolk sac was considerably higher in chicks from older parents incubated at HA, whereas, in contrast, levels of 18:3n-3 were lower. Also, chicks from younger parents in the HA treatment had lower transported 18:3n-3 and higher levels of transported DHA. It may be concluded that this process observed during the high incubation temperature may be related to a protective strategy and thus contributes to postnatal heat adaptation.

Key Words: parental age • heat acclimation • embryo composition • yolk sac composition • heat stress