[Show abstract][Hide abstract] ABSTRACT: Two experiments were conducted to test that broilers, reared under intermittent light program or fed a diet containing melatonin, would dampen the deleterious effects of heat stress on their performance and immune response. In the first experiment, two groups of one-day-old male broiler chicks received 23h Light: 1h Dark (CL), while another two groups received intermittent light (IL) (1hL: 3hD) programs. From 4-6 weeks of age, a group from each lighting program was exposed to heat stress (35 Ã‚Â°C). The other two groups were kept under 24 Ã‚Â°C. At 35 Ã‚Â°C, birds under IL program had 5 times less mortality and 41% higher body weight at six weeks of age compared to the CL birds. Moreover, heat-stressed birds under IL program had 11% better feed conversion and higher T<SUB>3</SUB> concentrations and antibody production, compared to the CL group. In the second experiment, two groups of one-day-old male broiler chicks were fed a diet containing 40 ppm melatonin (MEL) while another two groups received a MEL-free diet, from 4-6 weeks of age. Concurrently, a group from each MEL treatment was reared under 35 Ã‚Â°C. The other two groups were kept under 24 Ã‚Â°C. Under 35 Ã‚Â°C, birds receiving MEL had less mortality, better feed conversion and higher antibody production, compared to the MEL-free diet group. There were no significant differences in body weight, feed consumption and T<SUB>3</SUB> concentrations between these two groups. These results indicate that IL program may be used effectively to improve broiler's ability to alleviate the negative effects of heat stress more than MEL administration does.
International Journal of Poultry Science 08/2008; 7(8). DOI:10.3923/ijps.2008.749.756
[Show abstract][Hide abstract] ABSTRACT: Understanding the role of photoperiod regimens in regulating broiler performance and the immune response is becoming highly important. The objectives of the current investigation are to analyze the effects of photoperiod regimens on humoral and cell-mediated immune response as well as production characteristics in broiler chicken. A total number of 300 one day old male broiler chicks were divided randomly into three equal groups. For 6 weeks, the first group received continuous light (23L:1D) and the second and Third group received non-intermittent restricted light (12L:12D) and intermittent light (2L:2D) respectively. Intermittent light regimen induced activation of both peripheral T and B lymphocyte proliferation and energized antibody production significantly compared to the other two regimens. Furthermore, in the non-intermittent restricted light group, plasma Corticosterone concentration and H/L ratio were significantly higher compared to continuous and intermittent light groups. In addition, intermittent light treatment caused elevation of total white blood cells (WBC) and plasma T<SUB>3</SUB> concentration significantly compared to control. Moreover, intermittent light regimen reduced mortality rate 3 times and improved body weight by 10% compared to control. On the other hand, non-intermittent restricted light regimen had no effect on mortality rate, and suppressed body weight by 10% compared to control. In general, both intermittent and non-intermittent restricted light regimen improved feed conversion significantly compared to continuous light regimen. Even though the intermittent and non-intermittent restricted light regimens have the same period of darkness, the intermittent light regimen would be more beneficial than non-intermittent restricted light program.
International Journal of Poultry Science 07/2008; 7(7). DOI:10.3923/ijps.2008.665.671
[Show abstract][Hide abstract] ABSTRACT: Two experiments were conducted with male broiler chickens to study the effect of light program and melatonin injection on enhancing the immune response and reducing the inflammatory response induced by lipopolysaccharide (LPS) injection. In the first experiment, one-day-old broiler chicks were divided into two groups: The first group was exposed to continuous light (CL) (23L: 1D), whereas the other group was exposed to intermittent light (IL) (1L: 3D). At 6 wks of age, within each light program, chickens were injected intravenously (iv.) with either 3 mg/kg BW LPS, or with sterile saline. Blood samples were collected at 0, 3, 12 and 24 h post-injection. Total white blood cells (WBC), at 3, 12 and 24 h, were significantly higher in the IL-LPS group compared to the CL-LPS group. Body temperature and plasma corticosterone concentration at 3 and 12 h, were significantly lower in the IL-LPS group, compared to the CL-LPS group. Interleukin-1-like activity and IL-6 concentration were significantly lower in the IL-LPS group compared to the CL-LPS group at 3, 12 and 24 h. In the second experiment, 6 wk-old broiler chicks raised under CL, were divided into three groups. The first group was injected i.v. with 40 mg/kg BW melatonin, followed by 3 mg/Kg BW LPS 1 hour later. The second group was injected with saline followed by LPS 1 hour later. The third group received two saline injections 1 hour apart. Blood samples were collected at 0, 3, 12 and 24 h after the second injection. T lymphocyte proliferation were significantly higher in the melatonin-LPS group compared to the saline-LPS group. Plasma corticosterone concentration and body temperature were significantly lower in the melatonin-LPS group compared to the saline-LPS group at 3 h. IL-1-like activity and IL-6 concentration were significantly higher in the saline-LPS group compared to the other two groups at 3 and 12 h post injection. Total WBC was significantly higher in the melatonin-LPS group compared to the saline-LPS group at 12 and 24 hr. Our results indicate that intermittent light and melatonin injection can enhance the immune response and reduce the inflammation induced by LPS injection.
International Journal of Poultry Science 02/2008; DOI:10.3923/ijps.2008.193.201
[Show abstract][Hide abstract] ABSTRACT: Two experiments were conducted to study the effect of lighting program and melatonin addition to the diet on the immune responses of broiler chickens under chronic heat stress. In the first experiment, two groups of male broiler chickens received Continuous Light (CL) (23L: 1D) while another two groups received Intermittent Light (IL) (1L: 3D). From 4 to 6 wk of age, a group from each light program was exposed to 35 Ã‚Â°C versus 24 Ã‚Â°C for the other two groups. Heat stressed chickens under IL had significantly lower (p<0.05) body temperatures, pro-inflammatory cytokines levels and corticosterone concentrations in their plasma, compared to the heat stressed chickens under CL. Furthermore, in the heat stressed groups, the IL group had a significantly higher (p<0.05) cutaneous basophil hypersensitivity response and T-cell proliferation, compared to the CL group. In the second experiment, two groups of male broiler chickens were fed a diet containing melatonin (40 ppm), while the other two groups received a melatonin free diet (0 ppm), from 4 to 6 wk of age. Concurrently, a group from each melatonin treatment was exposed to 35 Ã‚Â°C versus 24 Ã‚Â°C in the other group. The heat stressed chickens receiving melatonin had significantly lower (p<0.05) body temperatures, pro-inflammatory cytokines IL-1 and IL-6 and corticosterone concentrations. Furthermore, in the heat stressed birds, the melatonin group had a higher but not significant cutaneous basophil hypersensitivity response and T-cell proliferation. The current study indicates that intermittent light and melatonin administration can be used to ameliorate immunosuppression associated with heat stress in broiler chickens.
International Journal of Poultry Science 09/2007; 6(9). DOI:10.3923/ijps.2007.651.660
[Show abstract][Hide abstract] ABSTRACT: The present study was conducted to determine the adverse effects of high temperature and humidity not only on live performance and egg quality but also on immune function in commercial laying hens. One hundred eighty 31-wk-old laying hens at peak production were used in this study. Hens were housed in cages (15 cages of 4 birds/cage) in each of 3 environmental chambers and received 1 of 3 treatments. The 3 treatments were control (average temperature and relative humidity), cyclic (daily cyclic temperature and humidity), and heat stress (constant heat and humidity) for 5 wk. Different production and immune parameters were measured. Body weight and feed consumption were significantly reduced in hens in the heat stress group. Egg production, egg weight, shell weight, shell thickness, and specific gravity were significantly inhibited among hens in the heat stress group. Likewise, total white blood cell (WBC) counts and antibody production were significantly inhibited in hens in the heat stress group. In addition, mortality was higher in the heat stress group compared to the cyclic and control groups. Even though T- and B-lymphocyte activities were not significantly affected by any of the treatments, lymphocytes from hens in the heat stress group had the least activity at 1 wk following treatment. These results indicate that heat stress not only adversely affects production performance but also inhibits immune function.