ABSTRACT

Two experiments were conducted to evaluate the effect of melatonin and lighting regime on physiological responses and reproductive traits of two strains of laying birds using 324 laying birds. Each of the experiments consisted of 162 birds.  Experiment I was with Nera Black strain while experiment II was with Isa Brown strain. Each of the experiments was grouped into 9 treatments which were further subdivided into three replicates of six birds each in a 2×3 factorial in a completely randomized design. Melatonin and lighting at three levels were administered to the birds four times weekly for 30 weeks. The three levels of melatonin were 0mg, 5mg and 10mg while lighting were 12 hours, 15 hours and 18 hours daily. Melatonin was dissolved in 2mls warm water and the birds were drenched while 100 watt bulbs were used to provide lighting. Data on physiological, performance, haematological and serum was evaluated. Results from the physiological responses showed that rectal temperature (RT), respiratory rate (RR) and heart rate (HT) were significantly (p<0.05) influenced by both melatonin and lighting regime in the two experiments. Melatonin at 5mg significantly (p<0.05) reduced the RT,  RR and HT with values of 41.55oC, 142.56 and 327.11 respectively in experiment I and 40.55oC, 139.44 and 320.22 respectively in experiment II. Melatonin at 5mg significantly (p<0.05) reduced the dust-bathing, feather pecking and panting in both experiments. Lighting regime increased dust-bathing and panting rate in experiment II but not in experiment I. Performance characteristics were significantly (p<0.05) influenced by both melatonin and lighting regime. The hen day egg production, feed conversion ratio and egg weight of 91.66%, 1.73 and 61.52g respectively for experiment II and 84.77%, 1.61 and 70g respectively for experiment I were recorded. This indicates that melatonin at all levels significantly (p<0.05) had superior effects in both experiments compared to lighting. The weight of the reproductive organs and the number of follicles were significantly (p<0.05) improved by melatonin in both experiments. Large yellow follicles and small white follicles increased significantly with increasing level of melatonin in both experiments. The haematological profiles were influenced by the administration of melatonin in both experiments. Significant differences (p<0.05) were observed in most of the serum biochemical parameters in both experiments. Significant (p<0.05) differences occurred in the hormonal profile. 15hrs lighting regime improved the body weight of the birds, size and number of developing follicles in both experiments. Interaction between melatonin and lighting improved the overall performance of the birds as the groups on 5mg of melatonin and 15hrs lighting performed better than the other groups in both experiments. It is therefore concluded that 5mg melatonin and 15 hours of lighting improved hen day egg production and development of follicles in Isa Brown birds. Nera Black on 5mg melatonin and 15 hours lighting had improved body weight gain and immune response thereby enhancing survival rate. It is therefore recommended that 5mg melatonin and 15 hours lighting should be used to enhance egg production and improve the behavioural characteristics of laying birds during thermal stress.