Effect of coat colour on heat stress among West African Dwarf sheep
This experiment was conducted to investigate the effect of coat colour on heat stress among West African Dwarf sheep. A total number of twenty-four West African Dwarf sheep with different coat colour types were used for the experiment. Rectal temperature (RT), respiratory rate (RR) and pulse rate(PR) were taken on each animal before sunrise and when they returned from grazing in the afternoon during late dry season ( January March) and early rainy season (April June ). Blood samples were collected for evaluation of packed cell volume (PCV), red blood cell count (RBC), white blood cell count (WBC), plasma sodium (Na+) and potassium (K+). Coat colour had significant (P<0.01) effect on PT, RR, PR and heat stress index (HI). Animals with black coat colour (aaB-SS) had the highest mean value for all parameters followed by brown mouflon and brown with extensive white, while the badger face coloured sheep(A-B-ss) had the least mean value. There were significant (P<0.01) differences between males and female in RT (38.69± 0.02 and 38.83± 0.02oC), RR (56.09± 0.58 and 59.94± 0.65 breaths/min), PR (74.67 ±0.39 and 77.92± 0.46 beats/min) and HI (1.60±0 0.19 and 1.63± 0.02) respectively. Season had significant (P<0.01) effect on RT, RR, PR, HI. Coat colour also had significant (P< 0.05) effect on RBC, WBC, Na + and K+. There were appreciable difference between female and male in RBC, WBC, Na+ and K+. Seasonal variation also significantly affected these blood parameters. However, PCV was not significantly (P>0.05) affected by variation in coat colour, sex and season. From the results obtained, it can be concluded that coat colour type had significant effect on heat stress in West African Dwarf sheep.
Keywords: Coat colour, heat stress, sheep, rectal temperature, respiratory rate, pulse