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1408
Effect of pelleting at different temperatures and times on nutrient supply of co-products form canola oil processing
The objective of this study was to evaluate effects of conditioning temperatures (70, 80 and 90°C) and conditioning time (50s and 75s) and their possible interaction during pelleting on predicted truly absorbed protein supply of canola meal. Truly absorbed protein supply were measured for dairy cows according to DVE/OEB system and NRC-2001 model. The treatments were designed in 3×2 factorial arrangement and experiment design was RCBD. Statistical analysis was performed using the PROC MIXED of SAS 9.3. The results showed that conditioning time had a quadratic effect (P<0.05) on total protein supplied to the small intestine (TPSI), microbial protein synthesized in the rumen based on available nitrogen (N_MCP), truly absorbed microbial protein in the small intestine (AMCP),rumen bypass feed crude protein (BCP) and truly absorbed bypass protein (ABCP). Samples conditioned at 80°C were highest in AMCP and N_MCP while lowest in TPSI and ABCP between pellets. Pelleting decreased (P<0.01) TPSI, BCP and ABCP (261.39 vs. 241.66 g/kg DM, 195.68 vs. 174.20 g/kg DM and 55.49 vs. 41.61 g/kg DM, respectively) but increased AMCP of canola meal (55.86 vs. 57.34 g/kg DM). Pelleting induced decreased truly digested protein in the small intestine (DVE; 99.26 vs. 86.77 g/kg DM) and increased degradable protein balance (OEB; 115.26 vs. 135.27 g/kg DM) were observed (P<0.01). In NRC-2001 model, affected by quadratic effect of conditioning temperature (P<0.05), samples conditioned at 80°C between pellets were lowest in rumen undegradable feed crude protein (RUP), truly absorbed rumen undegradable protein in the small intestine (ARUP) and metabolizable protein (MP). Rumen endogenous protein (ECP) and truly absorbed rumen endogenous protein in the small intestine (AECP) were decreased by increasing conditioning time (10.58 vs.10.21 g/kg DM and 4.23 vs. 4.08 g/kg DM, respectively; P<0.01). Pelleting decreased (P<0.01) MP, AECP and ECP of canola meal (107.09 vs. 94.65 g/kg DM, 4.43 vs. 4.16 g/kg DM and 11.08 vs. 10.39 g/kg DM, respectively). RUP and ARUP of canola meal were decreased by pelleting as well (176.29 vs. 156.94 g/kg DM and 49.99 vs. 37.49 g/kg DM, respectively; P<0.01). Summarily, pelleting changed potential protein supply of canola meal; alteration of pelleting conditions caused differences between pellets in predicted protein supply profiles.