MVSc

The draught performance of Bos indicus x Bos Taurus crossbred bullocks was compared with that of bullocks belonging to a South Indian draught breed (Kangayam type) under the agro - climatic conditions of Kerala, with a hot – humid tropical climate.
Two pairs of adult cross – bred bullocks (Jersey x Red Sindhi) and two pairs of adult indigenous bullocks (Kangayam type) were used for ploughing on dry land for 4 hours and 5 hours continuously on alternate days. Physiological responses like respiratory rate, pulse rate and rectal temperature and haematological parameters like haemoglobin per cent, erythrocyte sedimentation rate, packed cell volume, lactic acid and plasma bicarbonate were estimated before work, immediately after work and after 1 hour of rest after work. The dry matter intake and water intake on days of work and on days on which no work was done were measured and compared. In order to evaluate the relative efficiency of work, the average speed of walking and the total area ploughed in 1 hour were compared.
The cross – bred bullocks had significantly higher physiological responses even before the start of work. As a result of work the physiological responses increased significantly and during rest, the values declined but did not reach the pre – exercise values after one hour rest. The haemoglobin per cent of blood, packed cell volume and plasma bicarbonate content decreased significantly and the erythrocyte sedimentation rate and blood lactic acid content showed a significant increase as a result of work. One hour of rest was not sufficient to bring these parameters to pre – exercise values.
The indigenous bullocks consumed more dry matter per metabolic body size than the cross – breds. However, the total dry matter intake by the indigenous bullocks was less due to smaller body size. It was found that work had no effect on dry matter intake as the dry matter intake of indigenous and cross – bred bullocks on days of work and on days on which no work was done was almost similar. The cross – breds consumed more water per day matter per metabolic body size on days of work and no work.
The total area ploughed by indigenous bullocks in 1 hour was significantly more than the cross – bred bullocks. Also, the average speed of walking of indigenous bullocks was greater than that of the cross – breds.
The enhanced physiological reactions in the cross – breds even before the work pointed to the fact that they were under some degree of thermal stress due to the hot – humid climate. Exercise (work) increased the stress and widened the gap between the cross – breds and indigenous bullocks. The lower total feed intake and greater speed and more area ploughed per unit time make the indigenous Kangayam type bullocks a more economical animal. Their higher feed intake and lower water intake per unit metabolic size indicates that they can better sustain energy supply to the tissues for work and manage under lower water availability. Coupled with these advantages, their greater heat adaptability make them a superior draught animal.