|Lay Jr, Donald|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2003
Publication Date: 3/17/2003
Citation: SCOTT, K.A., LAY JR, D.C., SMITH, H.K., TOSCANO, M.J., WILSON, M.E. EFFECT OF THERMAL AND HORMONAL MANIPULATION OF DEVELOPING CHICK EMBRYOS ON POST HATCH BEHAVIOR AND PHYSIOLOGY. MEETING ABSTRACT. 2003. V. 86(SUPPL.2): ABSTRACT P. 2.
Technical Abstract: Stressors applied to pregnant mammals can affect the behavior and physiology of offspring. However, specific effects are difficult to determine due to confounding maternal variables. Developing chick embryos may prove an effective model in studying prenatal stress without maternal influence. Fertile eggs were assigned to one of 3 treatments, Heat, Corticosterone (Cort) and Control. Heat eggs were moved to a 40.6 C incubator on days 14, 17 and 19 of development for 24 hours. Cort embryos were treated with 60 ng corticosterone on days 14, 16, 18 and 20 of incubation, and Control eggs received no treatment. At approximately 9 days of age, 20 chicks per treatment were weighed and beak-trimmed. Birds were weighed periodically up to 7 weeks of age, at which time birds underwent Tonic Immobility (TI) or Open Field (OF) tests. Chickens were weighed and sacrificed at 11 weeks. The OF was 3.7 x 2.4 m, divided into 24 squares. Individual birds were placed in the OF for 15 minutes, after which a novel object was placed in the center of the pen. The test ended 15 minutes after object placement. Number of squares entered, time spent in outer, inner and corner squares, flapping of wings, and flying at the front of the pen were quantified. At hatch, Cort and Control birds weighed more than Heat (p=0.001). Cort chicks were heavier than Heat for the duration of the study (p=0.04), while Control birds weighed more than Heat through week 4 (p<0.05). No differences in duration of TI were found among treatments (p>0.10). Frequency of flying at the front of the pen for Heat was not significant in comparison with Control and Cort during the OF test (p=0.10). Chickens from all treatments behaved similarly, spending more time in outer squares and corners after novel object placement (p<0.0001 and p<0.05), while spending less time in inner squares (p<0.0001). Number of squares entered was lower following object placement, as was wing flapping (p<0.0001). Right adrenals of Cort birds weighed more than Control (p<0.05) but not Heat birds (p=0.08). These results indicate that prenatal stressors affect the physiology of chicks, but the effects of these changes on behavior, if any, require more investigation.