Corticosterone and fat deposition in broiler chicks: effect of injection time, breed, sex and age.

1. Corticosterone (680 micrograms/kg body weight per day) given as six daily injections to 3- or 7-week-old chicks decreased weight gain, but increased food consumption, abdominal fat pad weight, skin dry matter, relative liver size and liver fat concentration. 2. Time of day of injection did not modify the response to corticosterone of 3-week-old chicks kept under natural daylight nor of 7-week-old broilers receiving additional illumination. 3. Pure White Rock chicks and Cornish X White Rock crossbred chicks responded similarly to corticosterone at 3 weeks of age. 4. Seven-week-old female birds treated with corticosterone had significantly larger abdominal fat pads than similarly treated males. 5. Corticosterone injection was more effective in increasing the proportion of liver fat in 7-week-old birds than in 3-week-old chicks. 6. The increased amount of abdominal and liver fat due to corticosterone injections administered at 3 weeks of age disappeared after 3 weeks, but growth depression was still evident.