Effect of brooding conditions on the blood chemistry and performance of turkey poults

Abstract

Hematologic parameters and the levels of certain plasma metabolites offer an objective measure, and real-time insight into the physiological status of an animal. We hypothesized that blood chemistry analysis in brooding poults varies with even minor differences of temperature and can affect poult performance. A total of 2,240 one-day-old turkey hens were assigned randomly to 1 of 4 treatments [Control (C) = 32C and 60%RH; cold stress (CS) = 29C and 60%RH; heat stress (HS) = 35C and 60%RH; and heat stress plus humidity (HHS) = 35C and 75%RH]. In all the treatments, the temperatures were lowered 2°C the first week, and 1.5°C each week thereafter. The relative humidity was maintained constant, as much as possible, throughout the 35 d duration of the experiment. Brooding treatment affected pH, partial carbon dioxide (pCO₂), potassium (K), and sodium (Na). The treatments HS and HHS had higher pH and K, and lower pCO₂ and K in the blood. These changes suggest an attempt by the poults to cool down by increased water intake and panting. Furthermore, by the end of the experiment more birds in these 2 treatment groups had distended crops, possible to increased water intake also. The increase of ketone in the plasma, at 3 d of age, of poults from the 2 warmest brooding conditions (HS and HHS) suggests that these birds were consuming less feed and using more fat as its main fuel source. Furthermore, at 28 d of age significantly more poults from HS and HHS had reduced ventricular contractility of their hearts. However, no significant differences in the concentration of creatinine kinase (CK) or cardiac troponin I (cTnI) were found between treatments. In conclusion, this research revealed that blood parameters were influenced by minor temperature and humidity changes. Warmer brooding temperatures resulted in a higher incidence of pendulous crop. Overall, there were no significant differences in the estimated BW between the treatments. Further research is needed to optimize the number of samples needed and the time of sampling to optimize brooding conditions. We also need to investigate blood parameters that can reveal reduced contractility of the heart and if the reduced myocardial contractility from birds kept at a higher temperature and relative humidity predisposes them to dilated cardiomyopathy or other metabolic diseases.