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Abstract

Sixty steers were used in a feeding trial under confined conditions in which the utilization of sugar cane was studied. As complement, six different levels of molasses were utilized (X= 0.10, 0.36, 0.69, 0.97, 1.36 and 1.74 kg of dry matter/100 kg of live weight/day along with a fixed level of protein (0.237 kg/100 kg of live weight/day). The protein source was provided by urea (60%) and meat and bone meal (40%). Chopped sugar cane was offered ad. lib. The equation Y₁= 0.387 + 0.411 X – 0.081 X² (R²= 0.99, P<.01), described the positive effect of molasses on daily gain, Y₁, (kg/animal/day). The expected maximun intake of sugar cane was 1.318 kg of dry matter/100 kg of live weight/day (about 16.2 kg of fresh sugar cane/animal/day). Sugar cane consumption decreased with increasing levels of molasses, following the equation Y₂= 1.318e – 0.401 X (R₂= 0.97, P<.01), where Y₂ represents sugar cane intake in kg of dry matter/100 kg live weight/day. Total crude protein and metabolizable energy consumption were positively related to the level of molasses. The efficiency of utilization of food and metabolizable energy varied in a curvilinear fashion with increasing levels of molasses. The optimun efficiencies were lower than others obtained with different molasses rations. Live-weight increments obtained were caused by the increase in dietary energy trough the use of molasses. Sugar cane had a secundary role in providing the energy necessary for high daily gains, because it provided about 18 per cent of energy intake. This study includes input-output relations that allow to know the economical situation under any level of molasses and the main ration ingredients.