Researchers evaluate the effects of heat stress in poults

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USPOULTRY and the USPOULTRY Foundation announced the completion of a funded research project at North Carolina State University in which researchers evaluated the effects of heat stress in poults. The research was made possible in part by an endowing Foundation gift from Prestage Farms and proceeds from the International Poultry Expo, part of the International Production & Processing Expo (IPPE). The research is part of the Association’s comprehensive research program encompassing all phases of poultry and egg production and processing.

Dr. Rocio Crespo, Department of Population Health and Pathobiology, North Carolina State University, Raleigh, N.C

Project #F104: Blood chemistry led environment manipulations to reduce poult mortality

Dr. Rocio Crespo at North Carolina State University recently completed a research project to investigate the effect of heat stress on blood parameters as an objective measure of poult comfort and its association with early poult mortality. Findings indicated that heat stress may be associated with increased incidence of pendulous crop and decreased performance. However, further research is needed to better understand the effect of environment on blood chemistry.

Many turkey poults may experience poor starting performance for reasons that are not well understood. Turkey flocks may even suffer mortality up to 3% within the first three weeks of life. Factors, including delayed feeding, starvation, genetics and age of the parental flock have been investigated, but the true etiology remains elusive. Heat stress can cause serious physiological dysfunction that may result in heat stroke, cardiac dysfunction and death, yet its impact on young poult health has not been investigated. The only recognized measures of comfort in young birds today are subjective, such as visual (i.e., poult distribution) and noise (i.e., excessive noise may indicate inadequate temperature) observations.

Hematologic parameters and the levels of certain plasma metabolites offer an objective measure and real-time insight into the physiological status of an animal. Some analyzes change due to external stressors and health challenges before obvious behavioral or clinical signs are observed.

To investigate the effect of heat stress on blood parameters as an objective measure of poult comfort and its association with early poult mortality, the objectives of this project were to:
1) identify how temperature and relative humidity affect blood parameters of turkey poults.

2) investigate whether heat stress is associated with increased incidence of flip-over, dilated cardiomyopathy, higher mortality and overall poorer performance in turkey poults.

Four treatment groups were evaluated in the study, ranging from lowest temperature to highest temperature (T1, T2, T3 and T4). Maintaining temperatures and relative humidity within the target ranges was difficult due to the small variances in treatment group parameters. The brooding environmental temperature affected pH, partial carbon dioxide (pCO2), potassium (K) and sodium (Na) the most. The higher pH and lower pCO2 in treatments T3 and T4 were likely secondary to the poults’ effort to cool down through panting. Na was significantly depressed while K was increased in the two treatments with higher brooding temperatures (T3 and T4). While researchers did not measure water intake in each room, they hypothesized that the lower concentration of Na in the blood was due to increased water intake. Upon completion of the experiment, more birds in T3 and T4 groups had distended crops compared to poults in groups T1 and T2, possibly due to increased water intake. The increase of plasma ketones at 3 days of age for poults in T3 and T4 suggests that these birds were consuming less feed and using more fat as their main fuel source.

Findings supported the hypothesis that heat stress can be associated with increased incidence of pendulous crop and decreased performance. Further, warmer brooding temperatures may increase the incidence of dilated cardiomyopathy. There was not a significant difference in the concentration of creatinine kinase (CK) or cardiac troponin I (cTnI) between the groups. The results did not demonstrate that warmer brooding temperatures results in increased flip-overs. Low brooding temperatures were associated with higher mortality during the first week of age.

Further research is needed to better understand the effect of environment on blood chemistry. This research revealed that blood analysis could assist with the evaluation of poult thermal comfort in an objective manner.

The research summary can be found on the USPOULTRY website.
Information on other Association research may also be obtained by visiting the USPOULTRY website.