Doctoral Dissertations

Peter Osei

Date of Award

12-1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

K. R. Robbins

Committee Members

J. K. Miller, H. V. Shirley, H. Eiler, S. L. Melton

Abstract

Series of experiments utilizing broiler chicks were performed to determine the role of the pineal gland and light in chick growth and metabolic status. Chicks were pinealectomized, sham operated on, or left intact. Other groups of chicks were also treated with 15 ppm melatonin. The lighting schedules employed were (1) diurnal light/dark 16L:8D and (2) constant light or 24L:0D. The parameters measured were body weight gain, feed consumption and feed efficiency, energy retention, efficiency of energy utilization for gain, rate of hepatic lipogenesis, jejunal glucose absorption, as well as plasma triiodothyronine (T3) and throxine (T4) levels. Light treatment and dietary melatonin affected feed intake only slightly. However, gain, gain/feed ratio, and energy retention were significantly lower in birds housed under constant light. Dietary melatonin increased gain, gain/feed ratio, and energy retention by an average of 19%. The gain response to melatonin was significantly less when birds were housed under constant light; but there was not a significant light x melatonin interaction for either gain/feed ratio or energy retention. Pinealectomized birds grew significantly more slowly and less efficiently and were little affected by light treatment. However, the response of pinealectomized birds to dietary melatonin was of the same magnitude as either unoperated or sham operated birds. Constant light significantly depressed and dietary melatonin significantly increased liver lipogenesis, jejunal glucose uptake, and plasma T3 and T4 concentrations.

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