|Lay Jr, Donald|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/23/2002
Publication Date: 9/12/2002
Citation: LAY JR, D.C., WILSON, M.E., SCOTT, K.A., SMITH, H.K., TOSCANO, M.J. EFFECT OF ELEVATED THERMAL TEMPERATURE AND EXOGENOUS CORTICOSTEROID DURING INCUBATION ON THE PHYSIOLOGY OF CHICKENS. 2002. V. 5 (SUPPL.1): ABSTRACT P. 103.
Technical Abstract: Previous research in our laboratory has shown that exposing developing chick embryos on day 16 of incubation to either elevated thermal temperature or exogenous corticosterone can alter the behavior and physiology of the developing chick. The current study examined the effect of application of these two treatments over a 5 day duration. A preliminary study was first conducted, which applied [3H] - corticosterone to eggs at 16 days of incubation to determine the proportion of hormone that would cross the egg and bind in the chicken central nervous system. To test the application of treatments over several days, 240 eggs were assigned to one of three treatments: Heat, Corticosterone (Cort), or Control. Eggs in the Heat treatment were subjected to 24 hours of increased temperature, from 37.5 to 40.6 degrees C, on days 14, 17, and 19 of incubation. Eggs in the Cort treatment had 60 ng of corticosterone applied to the egg (600 ng applied with 10% absorption through the shell) on days 14, 16, 18, and 20 of incubation. Upon hatching, chicks were placed in one of two pens such that each pen held equal numbers of chicks from the three treatments. At 11 weeks of age, a jugular blood sample was collected from 30 chickens (n = 10/trt) immediately prior to sacrifice by cervical dislocation. The hypothalamus and raphe nucleus were dissected from each bird and snap frozen for analysis of epinephrine, norepinephrine, and dopamine.Application of [3H] - corticosterone indicated that the hormone does cross the shell of the egg and binds in the hippocampus of the developing chick. At 11 weeks of age we found that plasma corticosterone was not different between treatments (pooled mean +/- SE; 7.1 +/- .7 ng/mL; P > .80). Epinephrine, norepinephrine and dopamine concentrations did not differ between treatments (P > .17) in either the hypothalamus nor the raphe nucleus. Results from this study indicate that although exposure to exogenous corticosterone and thermal stress during incubation have been shown to alter the behavior of adult chickens in previous research, these alterations are not reflected in baseline concentrations of compounds important in controlling the animals response to stress.