Influence of dry heat treatment of canola meal on site and extent of nutrient disappearance in ruminants

Abstract

A study was conducted to determine the effects of temperature and duration of heating (125 or 145 °C for 10, 20 or 30 min) on ruminal, intestinal and total tract disappearance of the dry matter (DM) and crude protein (CP) fractions of canola meal. Two steers fitted with rumen and duodenal cannulas were utilized. The effects of heating on ruminal disappearance of DM and CP were determined by incubating samples in the rumen for 2, 4, 6, 8, 12, and 24 h. Partitioning DM and CP disappearance between the rumen, intestines (small and large) and total tract was accomplished using the mobile nylon bag technique. Relative to the unheated control meal, heating at 125 or 145 °C reduced ( P < 0.05) ruminal DM and CP disappearance. Relative to the control, no effects of heating to 125 °C were observed on intestinal DM or CP disappearance with the exception that samples heated for 20 or 30 min and incubated in the rumen for 24 h had higher ( P < 0.05) intestinal DM disappearance values. Heating to 145 °C reduced ( P < 0.05) intestinal DM disappearance relative to the control, particularly for samples heated for 30 min. Heating to 145 °C reduced ( P < 0.05) intestinal CP disappearance across all rumen incubation times. No differences between the control and meals heated to 125 °C were found in total tract DM and CP disappearance, indicating no negative effects of heating to 125 °C on nutrient digestion. Heating to 145 °C reduced ( P < 0.05) both total tract DM and CP disappearance. Acid detergent insoluble nitrogen content of the treated meal was negatively related to intestinal ( r 2 = 0.78) and total tract ( r 2 = 0.82) CP disappearance. It is concluded that heating CM to a temperature of 145 °C will reduce ruminal and total tract availability of the DM and CP fractions. Heating to 125 °C for 10, 20 or 30 min will reduce rumen disappearance of both DM and CP but will not significantly reduce the disappearance of CP over the total tract of the ruminant. These results indicate that short duration heating of canola meal to 125 °C, is an effective method of increasing rumen undegradable protein content without impairing intestinal digestibility.