Production and Physiological Parameters of Broiler Chickens Administered Chilled Drinking Water under High Ambient Temperature During Finisher Period

High environmental temperature is of great concern in production of broiler chickens in the tropics, and this experiment was conducted to evaluate the ameliorative effect of chilled drinking water on the production and physiological parameters of broiler chickens reared in the tropics. This 56 -day experiment contained 3 treatments (T 0 , T 1, and T 2 ), replicated 3 times to contain 16 birds per replicate. T 0 (control) was offered non-chilled drinking water without increasing ambient temperature; T 1 was offered non-chilled drinking water with an increased ambient temperature of 30°C between 11:30 – 15:30 GMT, daily; T 2 was offered chilled drinking water (8-10 ºC) with the increased ambient temperature of 30°C between 11:30 – 15:30 GMT, daily. The total body weight gain of the birds was similar (P> 0.05) in T 0 and T 2 , which were significantly (P <0.05) higher than that of T 1 . Feed intake was significantly (P<0.05) higher in T 0 than in T 1 and T 2 , which were similar (P>0.05), while feed conversion ratio (FCR) was significantly (P< 0.05) higher in T 1 than in T 0 and T 2 , which were similar (P> 0.05). Water intake was significantly (P<0.05) higher in T 2 than in T 1 , which was significantly (P<0.05) higher than the water intake of T 0 chickens. Hemoglobin (Hb) concentration and red blood cell (RBC) count were similar (P> 0.05) between T 0 and T 2 , which were significantly (P< 0.05) higher than values for T 1 . Packed cell volume (PCV), white blood cell (WBC), lymphocyte and platelet counts, and blood coagulation time were similar (P >0.01) between T 0 and T 2 , which were significantly (P <0.01) higher than those of T 1 . The serum globulin of T 0 chickens was similar (P>0.05) to that of T 2 , but significantly (P<0.05) higher than the serum globulin of T 1 chickens, which was similar (P>0.05) to that of T 2 . Serum sodium (Na+) and potassium (K+) ions were significantly (P< 0.05) higher in T 0 than in T 1 and T 2 , which were similar (P>0.05), while serum hydrogen carbonate ion (HCO 3- ) was significantly (P<0.05) higher in T 2 than in T 1 which was similar (P>0.05) to that of T 0 , and that of T 0 similar to that of T 2 . Respiratory rate and cloacal temperature were significantly (P ≤ 0.01) different among the treatments (T 1> T 2> T 0 ), while body temperature was significantly (P <0.05) higher in T 1 than in T 0 and T 2, which were similar (P >0.05). Therefore, administering chilled drinking water (8 -10 ºC) to broiler chickens during periods of high ambient temperature can ameliorate heat stress through improved FCR, weight gain, stabilization of blood parameters and constituents, and reduction of high respiratory rate, body, and cloacal temperatures.