Coat colour contributes to physiological adaptation in mammals and mediates response to thermal stress. Twenty-four adult West African Dwarf sheep of both sexes and with different coat colour types were used in this study. We measured rectal temperature (RT), respiratory rate (RR) and pulse rate (PR) before sunrise and sunset during the late dry season (January-March) and early rainy season (April-June) as well as packed cell volume (PCV), red blood cell (RBC) count, white blood cell (WBC) count, plasma sodium (Na(+)) and potassium (K(+)). Animals with black coat colour had the highest (P < 0.05) mean values of 38.92 ± 0.03 °C, 65.09 ± 1.06 breaths/min, 81.35 ± 0.78 beats/min, 1.70 ± 0.01 for RT, RR, PR and heat stress index (HSI), respectively, followed by brown mouflon and brown with extensive white, while the Badger Face coloured sheep had the least mean values. There were significant (P < 0.05) differences between male and female sheep for RT, RR, PR and HSI. Season had a significant (P < 0.05) effect on RT, RR, PR and HSI. Coat colour and sex also significantly (P < 0.01) affected RBC, WBC, Na(+) and K(+). Seasonal variation (P < 0.05) in all the blood parameters was observed, with the exception of PCV. Interaction effect of coat colour and sex was significant (P < 0.05) on RT and HSI. Correlation coefficients among the measured traits ranged from positive to negative values. These results indicate that selection of white-coloured sheep to attenuate heat stress is desirable in the hot humid tropics.
Rabbit production under tropical conditions is affected by environmental stress mainly from the effect of high ambient temperatures and high humidity, low wind speed and indirect solar radiation. This experiment was conducted to investigate the adaptive potentials of Californian, New Zealand white, Havana black and Palomino brown rabbits to heat stress when raised in humid tropics. A total number of ninety-six rabbits were used. Rectal temperature, respiratory rate, pulse rate and heat stress index were measured in these temperate breeds during rainy and dry season. The results showed that the breed of rabbit had a significant effect (P<0.05) on rectal temperature, respiratory rate, pulse rate and heat stress index. Havana black rabbit had the highest mean rectal temperature value (39.32 ± 0.03°C) followed by Palomino brown (38.97 ± 0.03°C), while the least value was recorded for New Zealand white (38.68 ± 0.02). Respiratory rate values followed the same pattern with that of rectal temperature with higher respiratory rate 69.09 ± 1.05 breaths/min recorded for Havana rabbits. The pulse rate values ranged from 163.23 ± 0.47 - 184.35 ± 0.78 beats/minutes. The highest pulse rate of 184.35 ± 3.78beats/minute was recorded for Havana black. The lowest heat stress index was obtained for New Zealand white followed by California and Palomino Brown while Havana black rabbit had the highest value (1.95± 0.01). The respiratory rate was significantly lower among males as compared to their female counterparts (63.09±0.58 versus 69.54 ± 1.65breaths per minute). The age of the rabbit also significantly affected (P<0.05) the rectal temperature, respiratory rate, pulse rate and heat stress index. 12 weeks old rabbit had the highest mean values while 4 weeks old rabbit had the least values. The heat stress index value obtained during dry season was higher (P< 0.05) than that obtained for rainy season (1.93± 0.02 versus 1.80 ± 0.01). Havana black rabbits and Palomino brown were more prone to heat stress than California and New Zealand white rabbits in tropical environment.
This study was carried out to evaluate the growth performance of Marshall, Cobb and Arbor acre strains of broiler chicken. A total number of three hundred (300) day-old broiler chicks of Arbor acre, Cobb and Marshall strains were raised under the same management condition. Data was obtained on the growth performance and analyzed. Cobb strain had the highest weight of 175.78 ± 2.51g at 2 weeks of age while Arbor acre and Marshall strain had similar (p>0.05) body weight at that age. Marshall had the highest body weight of 1804.37± 50.47g followed by Cobb with a weight of 1760.16 ±15.38g) while Arbor acre had the least body weight of 1683.43 ± 25.06g at 8weeks. Cobb strain had the highest body length (32.33 ± 0.10cm) at 8 weeks. All the strain studied had similar breast girth at 4 weeks. However, Marshall strain had the highest breast girth followed by Arbor acre while Cobb strain had the least breast girth at maturity. Marshall strain and Arbor acre had similar thigh lengths while the least thigh length was recorded for the Cobb strain. The effect of sex was significant (p<0.05) on all the growth parameters at 8weeks as male broilers had higher body measurements than their female counterparts. In conclusion, Marshall strain had better growth performance than Arbor acre and Cobb strain of broiler chicken.
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