Heat treatment of canola meal and subsequent availability of rumen escape protein and amino acids in ruminants
Onyango, Tobias Atali
As a continuing effort to increase the level of rumen escape protein and post ruminially available amino acids (AA) in high producing ruminants of today such as dairy cows in early lactation, three trials were conducted using three non-lactating Holstein cows fitted with rumen and T-shape proximal duodenal canulae; fifty adults Single Comb White Leghorn cockerels; and thirty two lactating cows. The purpose was to determine the effect of moist heat treatment of canola meal (CM) as a source of rumen escape protein as measured from in situ rumen and lower gastro intestinal (GI) tract degradability of: dry matter (DM), fiber, protein, essential (EAA) and non essential (NEAA); availability of EAA, NEAA and true nitrogen-corrected metabilizable energy (TMEn) in precision-fed cockerels; and feed intake, milk production, milk composition and body weight change in dairy cows in early lactation. Four different batches of commercial CM were exposed to moist heating at 110oC for 0 (CM 0), 23 (CM 23), 45 (CM 45) and 60 (CM 60) min through a steam jacketed conveyor and slowly steeped at passage rates of 200, 110 and 90 kg h-1 respectively. A bypass protein supplement (Bi) made from a mixture of animal-vegetable products was formulated for comparison with CM 60, based on similar calculated rumen escape EAA... (P<0.05) neutral detergent fibre (NDF), acid detergent insoluable nitrogen (ADIN) and neutral detergent insoluble nitogen (NDIN) contents. Rumen degradation of protein from CM 0 was higher (P<0.05) than other levels of heat treated CM. Type of protein in cows' diet affected (P<0.05) rumen protein degradation and subsequent rumen disappearance of nitrogen. Protein and EAA degradation was higher (P<0.05) in monofilament bag type than multifilament type. Lower GI tract degradation of protein from both bag types was not affected (P<0.05) by removal of pepsin-HCI digestion step. Heat treatment did not (P<0.05) change individual EAA and NEAA but tended to decrease (P<0.05) fecal excretion of arginine, leucine, lysine, methionine, and valine. Disappearance of EAA 12 h post rumen incubation was reduced (P<0.05) in the rumen but increased (P<0.05) in the lower GI tract with 60 min heat treatment and resulted in increased (P<0.05) fecal excretion of arginine, histidine, isoleucine, lysine, methionine and threonine. These changes resulted in an increased (P<0.05) 80-90% available EAA quantity in the small intestine... Results from these trials indicated decreased (P<0.05) rumen degradation of CM with increased heating, resulting in higher levels of protein and AA availability post-ruminally. Although the potential for rumen escape of heat treated CM increased P<0.05), milk yield and composition did not differ (P<0.05) from the unheated CM> It is suggested that higher temperatues above 110oC or longer heating times than 60 min be adopted with continued use of CM in dairy rations.