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- Physiologic responses of heatstressed broiler chickens (Gallus gallus...
Physiologic responses of heatstressed broiler chickens (Gallus gallus domesticus L.) subjected to early thermal conditioning and feed restriction
Dissertation Abstract:
Three experiments were conducted to evaluate the physiologic consequences of early thermal conditioning (ETC) and early feed restriction (EFR) in broiler chickens.
In Study 1, chicks were exposed to ETC (ambient temperature of 36 ± 1°C) for 24 h at d 3; 12 h at day 3 and 5; 8 h at day 3, 5, and 7; and control (no exposure). In Study 2, chicks were subjected to 60 percent feed restriction (EFR) at day 4, 5, and 6; day 7, 8, and 9; day 9, 10, and 11; and control (ad libitum feeding). A combination of ETC (38°C for 8 h at day 3, 5, and 7) and EFR (70% feed restriction at day 4, 6, and 8) using a 2 × 2 factorial design was employed in study 3.
Growth, body temperature, respiratory rate, hematocrit, total RBC, carcass, and bone ash were not affected regardless of the previous exposures to the two methods. Both ETC and EFR significantly reduced abdominal fat individually but not their combination. Free fatty acid levels were significantly different in EFR and ETC + EFR but not in ETC birds. Differential leukocyte count and H/L ratio did not vary except in Study 3, wherein a higher heterophil and lower lymphocyte count in ETC birds resulted to higher H/L ratio while monocyte values were highest in ETC and EFR birds and lowest in the untreated groups. No significant difference was observed in mortality rate.