Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 30, 2012
Publication Date: March 15, 2013
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2013. Interactive effects of photoperiod and light intensity on blood physiological and biochemical reactions of broilers grown to heavy weights. Poultry Science. 92:1029-1039. Interpretive Summary: The poultry industry has made rapid progress in improving the genetics and nutrition along with changes in environmental management, resulting in more rapid broiler growth. In order to maximize the genetic potential of modern heavy weight broilers (3.0 kg and above) while ensuring bird health, microenvironmental factors (light, air, temperature, humidity) recommendation are important. Although many studies have been conducted to evaluate the effect of the lighting programs in broilers production, still more studies are necessary to examine the interrelationship of photoperiod and light intensity related to the mechanisms that control the modern heavy broilers’ blood physiology (acid-base, electrolytes, metabolites, endocrine). Exposure of chicks to 3 photoperiods (long/continuous [23L:1D] from d 8 - d 56; regular/intermittent [2L:2D], and short/non-intermittent [8L:16D] from d 8 - d 48 and 23L:1D from d 49 - d 56, respectively) along with concurrent exposure to 3 light intensities (10, 5.0 and 0.5 lx) from d 8 through d 56 days of age on blood gases, electrolytes, acid-base balance, and their involvement on welfare in broiler chicken was examined. Result indicated that the effects of photoperiods were more pronounced than that of light-intensity on blood physiological variables and the conditions worsened as the length of photoperiods decreased. It was concluded that exposure of modern heavy weight broilers to short photoperiod in comparison with long/continuous and regular/intermittent photoperiods has a negative effect on some blood physiological variables. There was no effect of light intensity on most of the blood variables examined. In addition, the photoperiods and light intensity that we used in this study apparently did not act together or separately to affect plasma corticosterone that is a measure of well-being, suggesting that these factors may not pose as stressors to the modern heavy broiler chickens. The results indicate that continuous exposure of broiler chickens to low varying light intensities along with moderate photoperiod had a minor effect on blood physiological variables to enable them to maximize their genetic potential whereas a short photoperiod markedly affected most blood physiological variables without inducing physiological stress in broilers.
Technical Abstract: The effects of photoperiod, light intensity, and their interaction on blood acid-base balance, metabolites, and electrolytes in broiler chickens under environmentally controlled conditions were examined in 2 trials. The experiment was consisted of a factorial arrangement of treatments in a randomized complete block design. In each trial, all treatment groups were provided 23L:1D with 20 lx of intensity from placement to 7 d, and then subjected to the treatments. The 9 treatments consisted of 3 photoperiods (long/continuous [23L:1D] from d 8 - d 56; regular/intermittent [2L:2D], and short/non-intermittent [8L:16D] from d 8 - d 48 and 23L:1D from d 49 - d 56, respectively) and exposure to 3 light intensities (10, 5.0 and 0.5 lx) from d 8 through d 56 at 50% RH. Feed and water were provided ad libitum. Venous blood samples were collected on d 7, 14, 28, 42, and 56. Combined over days analysis indicated that short/non-intermittent photoperiod significantly (P < 0.05) reduced BW, pH, pO2, sO2, Na+, K+, Ca2+, Cl-, mOsm, T3, and TP along with significantly (P < 0.05) elevated pCO2, Hct, Hb, and lactate concentrations. In addition, there were no effects of photoperiod on HCO3-, glucose, anion gap, and T4. Plasma corticosterone was not affected by photoperiod, light intensity, or their interaction. There was no effect of light intensity on most of the blood variables examined. Acid-base regulation during photoperiod and light intensity exposure did not deteriorate despite a lower pH, and higher partial pressure of CO2 with normal HCO3- because of a compensatory increase in HCO3- concentration to normalize pH. These results indicate that continuous exposure of broiler chickens to varying light intensities had a minor effect on blood physiological variables, whereas the short photoperiod markedly affected most blood physiological variables without inducing physiological stress in broilers.