Impact of management systems on selenium and zinc levels, heterophil: Lymphocyte ratio as biomarkers of immunity in chickens

This study investigated the impact of poultry management systems (intensive and extensive) on selenium and zinc concentrations and heterophil to lymphocyte ratio in chickens. Sixty chickens comprising 20 broilers, 20 local chickens and 20 layers obtained from poultry markets and houses around Ibadan, Oyo State, Nigeria were used in this study. Five millilitres of blood were collected through the brachial vein to analyse for selenium, zinc and complete blood count using atomic absorption spectrophotometry and standard haematological methods, respectively. There was a significantly (P<0.05) higher red blood cell, haemoglobin and pack cell volume values in local chickens raised in the extensive management system compared to broilers and layers raised in the intensive management system. There was no significant difference (P>0.05) in the white blood cell count between layers and local chickens. However, layers had higher white blood cell counts than local chickens. In contrast, local chickens had significantly (P<0.05) lower white blood cell count than broilers. The respective lymphocyte and heterophil counts were significantly (P<0.05) higher and lower in local chickens raised extensively compared to layers raised intensively. There were no significant differences (P>0.05) in monocyte, eosinophil and basophil count in chickens raised from both management systems. Chickens raised in the extensive management system had a significantly (P<0.05) higher selenium concentration with a lower heterophil to lymphocyte ratio than those raised in the intensive management system but had a significantly (P<0.05) lower zinc concentration. Therefore, high selenium levels and low heterophil to lymphocyte ratio could contribute to the resistance of chickens to various stressors associated with an extensive management system as selenium is a known immunomodulator.