Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2013
Publication Date: 6/2/2014
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2014. Effects of genetic strain and light intensity on blood physiological variables of broilers grown to heavy weights. Poultry Science. 93:970-978.
Interpretive Summary: The poultry industry has made rapid progress in improving the efficiency of broiler growth and production through genetics, nutrition, along with changes in environmental management, resulting in more rapid broiler growth. This improvement in growth performance and carcass characteristics have come with physiological, immunological, biochemical, and anatomical changes and the consequences are not clear. Manipulation of lighting programs is a strategy used to reduce the incidence of metabolic and skeletal disorders in broiler chickens. Rate of development differs among genetic strains and lighting needs may be genetic strain specific in order to optimize growth performance. Most studies have not evaluated gradient levels of light intensity at ranges typically used in commercial practice on blood physiology of early- and late-developing broiler chickens. To address this knowledge gap, we investigated the effects of genetic strain, Ross × Ross 308, which has been selected for fast growth and high efficiency, and Ross × Ross 708, which has been selected for high yield and light intensity that are typical of those found in commercial poultry production on various blood physiological parameters in broilers grown to heavy weights under environmentally controlled conditions. We observed the effects of genetic strain on most of the examined blood physiological variables, but all these changes are still within the normal acid-base homeostasis ranges. However, there was no main effect of light intensity or strain by light intensity interaction on most of examined blood physiological variables. In addition, exposure of modern broiler strains to varying light intensity produced no effect on plasma corticosterone, suggesting that these levels of light intensities did not induce physiological stress in modern broiler strains. The results of this study supplement current knowledge of physiological response to differing lighting levels and may be used for further investigations on the health and respiratory physiology of early- and late-developing broiler strains grown to heavy weights. This study shows the positive influence on profits to commercial poultry facilities that are using low lighting environment to reduce energy utilization costs, hyperactivity, and pecking damage without physiological stress effects on broiler health.
Technical Abstract: The effects of genetic strain, light intensity and their interaction were examined on blood physiological variables of broilers maintained in environmentally-controlled rooms in each of 5 trials. The study consisted of a 2 × 5 factorial arranged in a randomized complete block design with 10 treatments of 2 strains (Ross × Ross 308 and 708) and exposure to 5 light intensities (25, 10, 5, 2.5, 0.2 lx) with chicks equally and randomly distributed at 1 d of age. The 5 light intensities were randomly assigned from d 22 to 56 d of age. Feed and water were provided ad libitum. Venous blood samples were collected on d 21 (base line), 28, 42, and d 56 of age. Main effects indicate that Ross × Ross 308 had significantly (P = 0.05) increased in BW, pCO2, Ca2+, Na+, Cl-, and T4 along with significantly (P = 0.05) reduced pH level, pO2, HCO3-, and T3 in comparison with Ross × Ross 708. There was no main effect of light intensity on all examined variables. In addition, there was no significant main effects of strain, light intensity or their interaction on sO2, Hct, Hb, K+, McHc, Glucose, mOsm and Anion gap. Physiologically, although Ross × Ross 308 had a significantly increased BW in comparison with Ross × Ross 708, but Ross × Ross 708 with significant (P = 0.05) increased in pO2, and T3 along with lower blood pCO2, and T4 will be physically more active. The results of this study supplement current knowledge of physiological response to differing lighting levels and may be used for further investigations on the health and respiratory physiology of early- and late-developing broiler strains grown to heavy weights. Plasma corticosterone was not affected by either treatments or strain indicating that the treatments did not induce physiological stress in broilers.