Circadian Rhythm of Hyla F1 Progeny and Grower Non- Descript Rabbits As Affected By Physiological Parameters Under the Tropical Conditions of Nigeria.
Circadian rhythm of physiological variables such as rectal temperature (RT), respiratory rate (RR) and heart rate (HR) were evaluated in the guinea savannah zone of Nigeria on three genetic groups (Hyla purebred, Hyla crossbred and grower non descript rabbits) at 64 days of age. Temperature humidity index (THI) was determined from the readings of AT and RH. Physiological and environmental readings were taken at 08:00 h to 10:00h in the mornings and 16:00 h to 18:00 h in the evenings from February through November, 2011. THI in the mornings was averaged 24.2 o C while evenings THI was averaged 27.8 o C. The THI values estimated averaged 27.3 o C during the cool period and 28.7 o C during the hot period. Overall, the results obtained indicated that THI in the evening was higher (P < 0.05) by 14% than THI in the morning. Also, THI in the hot was higher (P < 0.05) than THI in the cool season by 5%. There were significant (P<0.05) differences in the cycle of the day for all the thermoregulatory parameters (RR, HR, RT and ET) across the studied breed. The grower non descript rabbits showed the least values for both hour of the day for all the thermoregulatory parameters. In conclusion, grower non-descript rabbits had developed a better mechanism to adapt faster compared to the temperate Hyla rabbit during both cycles of the day.
Circadian rhythm; hyla rabbits; grower; non-descript; temperature humidity index
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