Comparative Study Ofthe Effects Of Season On Physiological Responses And Productivity Of Local And Exotic Breeds Of Layers

Abstract

The aim of this study was to evaluate the effects of season and breed on thermoregulation, blood constituents, blood metabolites, blood minerals, blood enzymes, egg production performance and egg quality in local and exotic breed (White Hisex) laying hens. The rectal temperature (Tr ) was significantly higher during the summer than the winter in both birds. The exotic breed showed significantly higher Tr than the local breed during summer and winter. The packed cell volume (PCV) was significantly lower during summer compared with winter in both breeds, and it was significantly higher in exotic breed than in local breed during summer. The haemoglobin concentration (Hb) was significantly higher in the exotic breed than the local breed in both seasons. The heterophil/lymphocyte ratio (H/L) was significantly higher during summer than the winter in both breeds. The plasma glucose level decreasedsignificantly during summer compared to winter in both breeds. The concentration of serum cholesterol was significantly higher during summer compared to winter in both breeds and it was significantly lowerin the local breed compared to the exotic breed during summer. Serum total protein concentration was significantly higher in exotic breed compared to the local breed only during summer. The serum Ca level decreased significantly during summer than the winter in both breeds and it was significantly lower in the local breed compared to the exotic breed in both seasons. Serum Na concentration was significantly lower in the local breed compared to the exotic breed during the summer and winter. Serum K concentration increased significantly during the summer compared to the winter in both breeds iv and was significantly lower in the local breed compared to the exotic breed during winter. The feed intake, egg production, egg weight and eggshell weight decreased significantly during the summerthan the winter in both breeds. These parameters also were significantly lower in the local breed compared to the exotic breed during summer and winter. The eggshell thickness was significantly greater in the exotic breed compared to the local breed in both seasons. Also the eggshell thickness was significantly lower during the summer compared to the winter in the exotic breed. The results indicated that the thermoregulation, haematological values, blood metabolites and blood electrolytes were affected by thermal load during summer inboth breeds. The summer hot environment was associated with decreased production performance (feed intake, egg production, egg weight and egg quality) in both breeds. These results have implications in environmental physiology and poultry industry under tropical conditions, were discussed critically in the light of the information previously reviewed in the literature