Melatonin and the Enhancement of Immune Responses in Immature Male Chickens

Abstract

Understanding the role of melatonin in affecting different physiological functions, especially immune responses, is becoming increasingly important in the basic and applied sciences. Enhancing the immune response will result in increasing disease resistance and, therefore, improve production efficiency. The purpose of the present study was to investigate the effects of melatonin, administered during the light or dark period, on BW, feed consumption (FC), and immune responses of immature chickens. Eight-week-old Cornell White Leghorn males were used in this study. The doses of melatonin were 0, 5, 10, 20, and 40 mg/kg BW. Melatonin was administered s.c. every 24 h for 7 consecutive d. The chicks were randomly divided into two groups; one group received injection during the middle of the light period, and the other group received injection during the middle of the dark period. All birds received 16 h light and 8 h darkness during a 24-h period. Body weights were measured before and after melatonin treatment, and FC was also measured. After the seven injections, blood samples were collected from the brachial vein, and total white blood cell (WBC) counts, differential cell counts, and activities of T and B lymphocytes were measured. Body weight was not significantly affected by dose of melatonin or time of injection. Furthermore, melatonin did not significantly affect FC; however, FC was significantly lower in the group that was injected in the dark vs. light period. The WBC counts of birds injected with 40 mg melatonin/kg BW were significantly higher than the WBC counts of saline-injected birds. The heterophil/lymphocyte (H/L) ratios of birds injected during the light period were significantly higher than those of birds injected during the dark period. T- and B-lymphocyte proliferation were significantly higher in birds injected with 40 mg melatonin/kg BW compared to saline-injected birds. These results indicate that melatonin in vivo is important in enhancing not only circulating WBC but also activities of B and T lymphocytes of immature male chickens without adversely affecting BW.

Melatonin implantation improved the egg-laying rate and quality in hens past their peak egg-laying age

“…It was reported that under stressful heat conditions, melatonin application improved the feeding efficiency of Japanese quail and reduced their oxidative stress47. Moreover, melatonin could enhance immunity in chickens against disease144849. As a result, these activities of melatonin may also help the hens preserve their egg-laying rate after their egg-laying peak age.…”

“…In birds, melatonin also functions as an immunoenhancement agent12. Its supplementation elevated cellular and humoral immune responses in Japanese quail13 and chicken141516. The signalling pathway analysis showed that both cellular and humoral immunoresponses triggered by melatonin were exclusively mediated by its receptor subtype MT2 (Mel 1b)17.…”

Seasonal immune function and sickness responses

“…Melatonin enhances in vitro production of interleukins and interferons by circulating human CD4 þ cells [53]. The number of white blood cells of chickens injected with melatonin was significantly higher than that of saline-injected birds [54]. Melatonin should not be considered a miracle drug, but it does have immunomodulatory effects that might have clinical relevance [55].…”

Effect constant and natural illumination on physiological state in rats

“…Особенно существенна роль мелатонина как иммуномодулятора при нарушениях иммунологического статуса, вызванных снижением эндогенного уровня гормона при функциональных и фармакологических воздействиях (Srinivasan et al, 2005;Moore et al, 2002). Уровень мелатонина положительно коррелирует как с гуморальным (Akbulut et al, 2001), так и с клеточным иммунитетом (Brennan et al, 2002;Champney et al, 1997). Введение экзогенного мелатонина в периоды, когда наблюдается снижение активности пинеальной железы (Nelson, Drazen, 1999;Haldar et al, 2001), приводит к усилению отдельных показателей иммунитета.…”