Physiological Responses of Slow-Growing Chickens under Diurnally Cycling Temperature in a Hot Environment
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Fundação APINCO de Ciência e Tecnologia Avícolas
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Free-range chicken production has signicantly increased in recent years and it often entails exposing birds to cyclic environmental conditions. The objective of the current study was to investigate the effect of bird strain and sex, and rearing system on the physiological responses of Potchefstroom Koekoek (PK), Ovambo (OV) and Naked Neck (NN) chickens reared in a hot environment. Body weight (BW), rectal temperature (RT), respiratory rate (RR) and heart rate (HR) were determined weekly for 4 weeks, in 3 slow-growing chicken strains under cyclic environmental conditions. A total of 288, 20-week old Potchefstroom Koekoek (PK), Ovambo (OV) and Naked Neck (NN) chickens were separated by sex and allocated to extensive and intensive rearing systems. Ambient temperature and relative humidity (RH) were used to compute a temperature humidity index (THI). A Proc MIXED model was used to analyze xed effects and a linear regression model was tted to test the relationship between THI and response parameters. All factor s studied inuenced ( p< 0.05) BW while none affected ( p> 0.05) RT. Higher BW ( p< 0.05) were obtained with OV in both rearing systems. Sex inuenced ( p= 0.0021) HR but not RR ( p> 0.05). Week and rearing system affected ( p> 0.05) RR. THI showed signicant correlation with RR and HR. THI was higher in intensive than extensive rearing. Physiological responses of PK, OV and NN are comparable under similar rearing conditions.
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