Circadian leucocytic and erythrocytic responses of Savannah brown goats to melatonin supplementation during the early rainy season

The research was conducted on two groups (n=5 per group) of Savannah brown goats with the aim of determining the circadian leucocytic and erythrocytic responses to daily oral melatonin supplementation during the early rainy season in Zaria, Nigeria. Melatonin(0.3mg/kg) was administered orally to the goats in one of the groups at 18:00 h of the day prior to taking blood sample and meteorological parameters at 6:00 h to 6:00 h of the next day. Experimental data for both groups were taken on days 1, 8 and 14 of the study periods. The overall mean circadian values of dry-bulb temperature, relative humidity and temperature-humidity index were 29.13 ± 1.21 ºC, 59.8 ± 5.70 % and 77.94 ± 1.09, respectively. The relative humidity values correlated significantly (P < 0.05) positive with the total white blood cell counts of the control (r = 0.2204) and melatonin-administered (r = 0.2792) groups and with the lymphocyte count (r = 0.2550) of the melatonin-administered group only. The total white blood cell counts at 12:00 h of day 1, neutrophil count at 6:00 h of day 14 of the melatonin-administered bucks were significantly (P < 0.05) higher than their corresponding control values. The overall circadian monocyte counts of day 8 was significantly (P < 0.01) higher in the control group. There was no significant difference between the examined erythrocytic parameters in the two groups. Inferentially, the oral melatonin administration to the bucks at 18:00 h seemingly boosted the immune status of the bucks during the early hours of the next day.