Submitted to: International Journal of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 2011
Publication Date: September 30, 2011
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2011. Effect of varying light intensity on blood physiological reactions of broiler chickens grown to heavy weights. International Journal of Poultry Science. 11(2):81-87. Interpretive Summary: Although many studies have been conducted to evaluate the effect of light intensity on broiler performance, behavior and welfare, still more studies are necessary to examine how light intensity affects the mechanisms that control the bird’s physiology (acid-base, electrolytes, metabolites, endocrine). Determination of these factors are essential so that therapeutic or nutritional strategies can be applied to reduce negative effects, if any, and thereby optimize the environment in broiler houses to maximize the genetic potential of birds while reducing production costs. Most studies have not evaluated gradient levels of light intensity at ranges typically used in commercial practice on blood physiology with modern early- and late-developing broiler production systems. To address this knowledge gap, we evaluated the specific effects of varying levels of light intensities (25, 10, 5, 2.5, and 0.2 lx) on various blood physiological parameters in broilers grown to heavy weights under environmentally controlled conditions. Results indicated that lowest light intensity of 0.2 lx only altered some of examined blood physiological variables, but all these changes are still within the normal acid-base homeostasis physiological ranges. In addition, exposure of modern heavy broilers to varying light intensity produced no effect on plasma corticosterone, suggesting that these levels of light intensities pose no stressors to the modern heavy weight (> 2.5 kg) broiler chickens. This study shows the positive impact on profits to commercial poultry facilities that are using low lighting environment to reduce hyperactivity, pecking damage, and energy costs while ensuring poultry welfare and well-being.
Technical Abstract: This study investigated effects of varying levels of light intensities (25, 10, 5, 2.5, and 0.2 lx) from 22 to 56 d of age at 50% RH on blood acid-base balance, metabolites, and electrolytes of heavy broilers reared under environmentally controlled conditions. Four identical trials were conducted with two replications per trial. In each trial, 600 1-d-old Ross 308 chicks were randomly distributed into 10 environmentally controlled chambers (30 males and 30 females chicks/chamber). Each chamber was randomly assigned one of five light intensities from d 22 to 56 d of age. Birds were provided a four phase-feeding program (starter: 1 to 14 d, grower: 15 to 28 d, finisher: 29 to 42 d, and withdrawal: 43 to 56 d). Feed and water were provided ad libitum. Venous blood samples were collected on d 21 (base line), 28, 42, and 56. Lowest light intensity of 0.2 lx significantly (P = 0.05) increased pH, Na+, K+, Cl-, and reduced pCO2, Hb, and Hct. However, all these acid-base changes are still within the normal acid-base homeostasis physiological ranges. In addition, exposure of modern heavy broilers to varying light intensity produced no significant effect on pO2, sO2, Ca2+, mOsm, McHc, Angap, T3, T4 and CS. Acid-base regulation during light intensity exposure did not deteriorate despite a lower pCO2 that consequently increased blood pH due to a compensatory mechanism for mild alkalosis. This study shows the positive impact on profits to commercial poultry facilities that are using low lighting environment to reduce hyperactivity, pecking damage, and energy costs without the induction of physiological stress effects on broiler welfare.