COMPARATIVE-STUDY OF RECTAL TEMPERATURE AND OF THE 24-HOUR ACTIVITY IN CATTLE (HOLSTEIN-FRIESIAN AND SIBONEY-DE-CUBA) ON TROPICAL PASTURE

The level of heat tolerance of Holstein Friesian and Siboney de Cuba ( 5/8 Holstein Friesian x 3/8 Zebu) lactating cows was studied during th e dry- and the rainy season in the tropical climate of Cuba. Beside th e rectal temperature (Tr) the proportion of coupling between the rhyth m of a natural Zeitgeber like the light/dark cycle and the daily cours e of locomotory activity primarily endogenously regulated could be a s ign for trouble on some environmental influences. There were no differ ences of the degree of thermal load for both breeds in the dry season. In the rainy season the Holstein Friesian cattle had a higher level o f rectal temperature (Tr) than Siboney de Cuba even in the early morni ng. In the afternoon the Tr exceed the threshold temperature for a the rmal load (39-degrees-C) only in Holstein Friesian cattle. This indica tes a thermal load for this purebred taurine cattle in the rainy seaso n. In the rainy season a lower degree of synchronization between the r hythm of activity and the light/dark-cycle for Holstein Friesian cattl e was found. The calculated coupling degree was significantly lower fo r the purebred taurine cattle.