Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/19/2010
Publication Date: 12/15/2010
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2010. Effect of ambient temperature and light intensity on physiological reactions of heavy broiler chickens. Poultry Science. 89:2719-2725. Interpretive Summary: The genetic potential of modern heavy broilers (2.5 kg and above) breeds for high productivity will not be fully realized until microenvironmental constraints (temperature, humidity, light intensity, air velocity, etc) have been fully addressed. Although many studies have been conducted to evaluate the effect of the thermal environment in broilers, still more studies are necessary to examine the interrelationship of temperature and light intensity in affecting the mechanisms that control the modern heavy broilers’ physiology (acid-base, electrolytes, metabolites, endocrine). Exposure of chicks to ambient temperatures of 15.5, 21.1, and 26.7 °C from 21 to 56 days of age concurrently with differing light-intensities (0.5, 3.0, and 20 lx) on blood gases, electrolytes, acid-base balance, and their involvement on welfare in broiler chicken was examined. Result indicated that the effects of ambient temperatures were more pronounced than that of light-intensity on blood physiological variables and the conditions worsened as the level of ambient temperatures increased. It was concluded that exposure of modern heavy weight broilers to high ambient temperature of 26.7 °C in comparison with low and moderate ambient temperatures has a negative effect on some blood physiological variables. In addition, the high ambient temperature 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 of this study show the positive impact of reducing microenvironmental factors (temperature and light intensity), suggesting that modern heavy broilers need to be grown under lower ambient temperature than previously reported due to their higher body weight and metabolic rates to enable them to maximize their genetic potential while reducing production costs.
Technical Abstract: The effects of ambient temperature, 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. The 9 treatments consisted of 3 levels (Low=15.6, Moderate=21.1, High=26.7 °C) of temperatures and 3 levels (0.5, 3.0, 20 lx) of light intensities from d 21 to 56 d of age at 50% RH. Five hundred and forty Ross 708 chicks were randomly distributed into 9 environmentally controlled chambers (30 males and 30 females chicks/chamber) at 1 d of age. Feed and water were provided ad libitum. Venous blood samples were collected on d 21 (base line), 28, 42, and 56. High ambient temperature significantly (P = 0.05) reduced BW, partial pressure of CO2 (pCO2), bicarbonate, hematocrit, hemoglobin, K+, and Na+ along with significantly (P = 0.05) elevated pH level, Cl-, glucose, osmolality, and anion gap concentrations. Partial pressure of O2 (pO2) was slightly increased in response to increased ambient temperature. There was no effect of light-intensity on most of the blood variables examined. Acid-base regulation during high ambient temperature and light intensity exposure did not deteriorate despite a lower pCO2 that consequently increased blood pH, due to a compensatory decrease in HCO3- concentration. Plasma corticosterone was not affected by temperature, light intensity or their interaction. These results indicate that continuous exposure of broiler chickens to high ambient temperature, high light intensity or their combination, markedly affects various blood variables without inducing stress in broilers.