Effect of Roasting Temperatures on Soybean Utilization by Young Dairy Calves1,2

Abstract

Diets containing soybeans roasted at different temperatures were fed to investigate effects on growth and feed consumption by calves. In trial 1, Holstein calves (n = 71) were used from birth to 10 wk of age. Three of the diets contained 18% CP and soybeans roasted to achieve exit temperatures of 99, 127, or 143°C and air cooled immediately after they exited the roaster; the fourth diet contained 15% CP and soybeans roasted at 127°C. Calves fed the diet containing soybeans roasted at 143°C consumed more feed, gained mote BW, and were more efficient in converting feed and energy to gain than those fed soybeans roasted at 99 or 127°C. Performance was intermediate by calves fed the diet containing 15% CP. In the second trial, 84 Holstein calves were used from 0 to 8 wk of age and were fed diets containing soybeans that had been roasted to achieve exit temperatures of 132, 146, or 163°C, followed by 30min of steeping. performance of calves fed soybeans processed at 146°C was superior to that of calves fed soybeans processed at 132 or 163°C. Rumen-undegradable intake protein, determined by a protease method, increased with increasing roasting temperature, but unavailable protein, as calculated from ADIN, was high for soybeans roasted at 163°C. Lipase activity decreased with increasing roasting temperature and was absent for soybeans toasted at 163°C. Roasting temperatures that resulted in superior calf performance corresponded to corrected undegradable intake protein (undegradable intake protein minus indigestible intake protein) of 50 to 60% and a trace of lipase activity.