Author:

Keywords:

temporal secretory patterns, growth-hormone, chickens, protein, lines, Science & Technology, Life Sciences & Biomedicine, Agriculture, Dairy & Animal Science, Agriculture, TEMPORAL SECRETORY PATTERNS, GROWTH-HORMONE, CHICKENS, PROTEIN, LINES, 0702 Animal Production, Dairy & Animal Science, 3003 Animal production

Abstract:

In the present experiment, the effect of the intermittent lighting schedule 1 h light (L):3 h darkness (D) on energy and nitrogen metabolism of female broilers at different ages was compared with continuous illumination (24L:0D) by using open circuit respiration chambers. Changing from continuous to intermittent lighting at 9 days of age induced a transient depression in growth rate that was followed by compensatory-growth. At a younger age, when growth was retarded, chickens reared under 1L:3D produced less heat per kilogram metabolic body weight, retained more energy as protein, retained dietary protein with a higher efficiency and deposited less fat, resulting in a higher protein: fat ratio of the achieved body weight gain. At 35 days of age, when compensatory growth was manifested, chickens reared under 1L:3D produced more heat which can be explained by the leaner body weight gain. The efficiency of dietary protein retention was also higher for chickens kept in intermittent than in continuous lighting. At 44 days of age however, the protein:fat ratio was lower for the heavier 1L:3D chickens. It is suggested that when the growth trajectory is altered by imposing intermittent lighting at a young age, the onset of the fat growth wave is postponed initially but does not persist when chickens attain a heavier body weight.