INFLUENCE OF DRY HEAT-TREATMENT OF CANOLA-MEAL ON SITE AND EXTENT OF NUTRIENT DISAPPEARANCE IN RUMINANTS

A study was conducted to determine the effects of temperature and dura tion of heating (125 or 145 degrees 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 ru men and duodenal cannulas were utilized. The effects of heating on rum inal 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 disa ppearance between the rumen, intestines (small and large) and total tr act was accomplished using the mobile nylon bag technique. Relative to the unheated control meal, heating at 125 or 145 degrees C reduced (P < 0.05) ruminal DM and CP disappearance. Relative to the control, no effects of heating to 125 degrees C were observed on intestinal DM or CP disappearance with the exception that samples heated for 20 or 30 m in and incubated in the rumen for 24 h had higher (P < 0.05) intestina l DM disappearance values. Heating to 145 degrees C reduced (P<0.05) i ntestinal DM disappearance relative to the control, particularly for s amples heated for 30 min. Heating to 145 degrees C reduced (P < 0.05) intestinal CP disappearance across all rumen incubation times. No diff erences between the control and meals heated to 125 degrees C were fou nd in total tract DM and CP disappearance, indicating no negative effe cts of heating to 125 degrees C on nutrient digestion. Heating to 145 degrees C reduced (P < 0.05) both total tract DM and CP disappearance, Acid detergent insoluble nitrogen content of the treated meal was neg atively 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 degrees C will reduce ruminal and total tract availability of the DM and CP fractions. Heating to 125 degrees C for 10, 20 or 30 min will reduce rumen disappearance of both DM and CP but will not signif icantly reduce the disappearance of CP over the total tract of the rum inant. These results indicate that short duration heating of canola me al to 125 degrees C, is an effective method of increasing rumen undegr adable protein content without impairing intestinal digestibility.