RESUMO
In semiarid parts of Africa animal traction is still one of the most reliable sources for rural work power. However, draught animals have to produce most of their work power at an unfavourable moment of the year that is at the end of the dry season when feedlot is scare. To improve their condition prior to the planting season, a short training could help. The effect of training can be expressed by the changes in contents of Na(+), K(+)-pumps in the muscle cell membrane. After a training period of 15 days all cattle showed a mean increase in Na(+), K(+)-ATPase of 24% (P < 0.01) in the semitendinosus muscle of the hind leg, whereas the control group showed no change. Bulls demonstrated already after 8 days of training an increase of 20% (P < 0.05). The principal factor responsible for this up-regulation of the Na(+), K(+)-pumps is most probably the excitation of muscles during exercise. In the course of the 15 days training period, the surge of plasma K(+) in during exercise showed a tendency to decrease, but this was not significant. Nevertheless, the reduced elevations of plasma [K(+)] may delay the moment of fatigue and so improve endurance. In conclusion, a training period of 8-15 days improves the contents of Na(+), K(+)-pumps and so the possible work output of draught cattle.
