Genetic adaptive potentials of four breeds of rabbit to heat stress in the humid tropics

Abstract

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.