PHYSICAL PERFORMANCE, ENERGY-REQUIREMENTS AND PHYSIOLOGICAL ADAPTATIONS OF DRAFT HORSES WHEN PLOWING

A study to determine the performance and energy requirements needed to plough clay soils of the Quella series for rice crops was carried out . At the same time, to obtain effort indicators the power developed by horses was related to physiological and morphometric variables. With this purpose, five chilean draught horses, which pulled a mould board plough for five hours a day were used. The draught force (kN), distanc e (m), working time (s) and tile work done (kJ) were measured by an Er gometer. The width, depth and area of work were also measured. Theoric and effective work capacity as well as the field efficiency were calc ulated with these parameters. The heart rate was recorded and blood sa mples for lactic acid determination were taken previous to, during and alter ploughing. The horses developed a draught force of 0.91 kN and worked at 3.74 km/h. The depth and width of work were 8.85 and 20.66 c m respectively, ploughing an area of 3021 m/journey, with an energy re quirement of 14268 Kcal/journey. The theoric work capacity was 0.0982 ha/hr, while the effective capacity was 0.0667 ha/hr, giving a field e fficiency of 68%. The power developed by the horses reached 94.4 kgm/s ec, which is 16.4% higher than the estimated working capacity accordin g to body weight, indicating that the horses made a draught effort gre ater than their normal capacity. The over-effort was significantly cor related with increased heart rate and Lactic acid concentration. It is concluded that the measurement of heart rate and blood lactic acid co ncentration are good indicators of the effort level that draught horse s make during ploughing.