Leukocyte Responses to Acute Heat Stress in Turkey Toms Either Fed Restricted or Ad Libitum During Growth Period


XXII World Poult. Cong.,, Türkiye, 1 - 04 Mayıs 2004

  • Basıldığı Ülke: Türkiye


The effect of environmental stressor, climatic or nutritional, on avian leukocyte has been widely considered in a number of researches. Leucocyte responses are considered as better indicators of stress. Heterophil:lymphocyte (H:L) ratio in the avian blood refers to stress status only when mild to moderate stress exist. However, extreme stress conditions result in a heterophenia and basophilia. Several reports showed that food restriction resulted in significant basophilia in broilers and ducks except with turkeys. The effects of climatic changes or food restriction on turkeys have not received a high level of attention. The food restriction is not commonly used in turkey production except in compensatory growth studies and breeders. Turkeys are also known to be less sensitive to heat stress due to better heat dissipation from their relatively large wattles. However, economic losses in poultry production due to acute heat waves during summer season are of importance in many parts of Turkey. Therefore, this study investigated the differential of leucocyte cell counts, H:L ratio, and body temperatures of turkey toms close to marketing age under acute heat exposure. A total of 28 commercial heavy line turkey toms which had been subjected to two different feeding regimen either restricted (intermittent) including consequent two h of on-feed and off-feed periods that give a total of 8 h feeding time in each day or ad libitum till 15 wk were used in the present study. At 15 wk of age, 14 birds from each feeding group were randomly chosen, were bled, and rectal temperatures were measured. Birds were gently moved to warm room where mean temperature and humidity was 31.85±0.31 °C and 51.19±0.70% during the 2 h of heat exposure of turkey toms. Heat stressed birds were bled for leucocyte counts and body temperatures were measured. Feeding treatment which was used during rearing period did not affect the leucocyte response and body temperature of turkey toms. Body temperature, heterophils, basophils, and monocyte proportions , and H:L ratio increased with acute heat exposure while the lymphocytes lowered. Eosinophil remained unchanged under acute heat stress. In conclusion, significant arise in basophil numbers reported here and lowered lymphocytes accompanied with high H:L ratios showed the severe effect of heat stress on turkey toms, either fed restricted or ad libitum during growth period, under the experimental conditions . Keywords: turkey tom, heat stress, leucocyte, H:L ratio, body temperature