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Relative importance of ear surface area on heat tolerance of composite rabbit population was evaluated. The study was conducted during the dry and rainy seasons, climatic data were recorded to obtain categorical heat stress index. Physiological parameters, growth performance, ear length and ear width of the rabbits were taken. Data collected were analysed using product-moment correlation analysis to show the relationship between ear surface area, growth traits and physiological traits (rectal temperature, respiratory and pulse rates) of the rabbits; trends of seasonal variation in THI, temperature and relative humidity within each season was monitored by Frequency Procedure of Statistics Analysis System SAS (2004). Moderate to high correlations (r = 0.43 – 0.61) were observed between growth traits and ear length; also high correlations (r = 0.57 and 0.80) were observed between respiratory rates, pulse rates and ear length. However, low correlations (r = 0.27) were detected between ear length and rectal temperature. Low correlation (r = 0.12) was observed between body weight and ear width. There were no correlations between ear width, respiratory rates and pulse rate. However, a residual correlation (r = -0.03) was obtained between ear width and body temperature. Large ear surface area in composite rabbits enhances better physiological performance and growth performance in hot climates.
Keywords: Composite rabbits, ear surface area, growth traits, physiological traits, season