Physiological responses of broiler chickens to heat stress and dietary electrolyte balance (sodium plus potassium minus chloride, milliequivalents per kilogram).
Individually caged male Cobb broilers (24), 44 d of age, were used to evaluate effects of heat stress (1 d of data collection) and dietary electrolyte balance (DEB; Na + K - Cl, mEq/kg from 1 d of age). During summer rearing, mortality was variable, but DEB 240 improved growth, feed conversion ratio, water intake, and water:feed ratio vs. DEB 0. The temperature sequence for heat stress was 24 to 32 degrees C in 30 min, 32 to 36 degrees C in 30 min, 36 to 37 degrees C in 15 min, and 37 to 41 degrees C in 45 min. Maximum temperature was held for 15, 60, 90, or 360 min for data collection (relative humidity averaged 42 +/- 7%). Results from the same room before and after heat stress were analyzed by DEB (1-factor ANOVA) and before vs. after heat stress compared across DEB (2-sample t-test). Heat stress decreased blood Na, K, and pCO2, and lymphocytes but increased heterophils. Blood HCO3 rose, Cl declined, and hematocrit gave a concave pattern (lowest at DEB 120) as DEB increased. After heat stress, DEB 0 decreased blood Na and K, and DEB 0 and 120 levels decreased blood HCO3. After heat stress blood pCO2 and hemoglobin decreased with DEB 240, but it had highest pCO2, a key factor. The DEB 120 gave longest times to panting and prostration with DEB 0 and 240 results lower but similar statistically. In heat stress, DEB 360 was excessive, DEB 120 and 240 were favorable, and DEB 0 was intermediate based on hematology, panting, and prostration responses.
Borges
S A
SA
Hooge Consulting Service, Inc., 8775 North Cedar Pass Road, Eagle Mountain, Utah 84043, USA.
Fischer da Silva
A V
AV
Majorka
A
A
Hooge
D M
DM
Cummings
K R
KR
D000136:Acid-Base Equilibrium / Q000502:physiology; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D002645:Chickens / Q000502:physiology*; D004032:Diet; D004326:Drinking / Q000502:physiology; D004573:Electrolytes / Q000097:blood; D006128:Growth / Q000502:physiology; D006359:Heat Exhaustion / Q000503:physiopathology; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006454:Hemoglobins; D008214:Lymphocytes / Q000097:blood / Q000166:cytology; D008297:Male; D009504:Neutrophils / Q000166:cytology; D014882:Water-Electrolyte Balance / Q000502:physiology*
D004573:Electrolytes; D006454:Hemoglobins; D002245:Carbon Dioxide