Effect of melatonin and lighting regime on physiological responses and haematological profile of isa brown laying birds

Abstract

Background: Melatonin is the main neurohormone synthesized and released by the pineal gland. It stimulates several antioxidative enzymes which increase its efficiency as an antioxidant and enhance the maturation of oocytes and the development of follicles in animals. Artificial lighting on the other hand improves bird’s performance especially reproductive performance and behavior. By providing artificial light, growers can manipulate this natural cycle to their advantage and increase the egg laying. Therefore, this current study was aimed to evaluate the effect of melatonin and increased lighting on the welfare of laying birds. Methods: In November 2018 to December 2019, a total 162 sixteen weeks Isa Brown hens were used for the experiment which was grouped into 9 treatments. Melatonin and lighting at three levels (0mg, 5mg, 10mg and 12hrs, 15hrs and 18hrs) were administered orally to the birds four times weekly within a day interval for 30 weeks from 16 weeks to 46 weeks. Data on rectal temperature, respiratory rate and heart rate were collected and analysed. Blood samples were also collected and analysed for haematological parameters Result: Results showed that rectal temperature (RT), respiratory rate (RR) and heart rate (HT) were significantly (p<0.05) influenced by both melatonin and lighting. Melatonin at 5mg significantly (p<0.05) reduced the rectal temperature (40.55°C), respiratory rate (139.44bpm) and heart rate (320bpm) while lighting at 18 hours significantly (p<0.05) increased the rectal temperature, respiratory rate and heart rate due to heat stress among the parameters. The haematological profiles were influenced (p<0.05) by the administration of melatonin. Treatments levels on melatonin administration (5mg and 10mg) had increased circulating packed cell volume of 28.00% and 28.11% respectively compared to the control group which had 25.66%. The results indicates that melatonin at 5mg and 10mg improved the welfare of the birds but increased lighting beyond 12 hours compromised immunity of the birds.