Abstract
The nutrient composition and enzymatic in vitro nutrient digestibility of raw full-fat soybean (RFSB) were assessed prior to evaluating the influences of enzyme supplementation in diets in which commercial soybean meal (SBM) was partially (phase 1) or completely (phase 2) replaced by RFSB. A 2 x 2 + 1 arrangement was used in a two-phase feeding trial. In phase 1 (0 - 25 days) a positive control, commercial-type diet (PC), without RFSB or enzymes, and a negative control diet (NC), with 75 g RFSB/kg were used. The NC diet was supplemented with or without protease (0 or 15000 PRPOT/kg) and phytase (0 or 2000 FYT/kg). In phase 2 (26 - 31 days), RFSB (NC) or SBM (PC) was used as the sole source of crude protein (CP) for birds. Each treatment was replicated six times. Phases 1 and 2 had the same enzyme supplementation and treatment arrangements. The results showed that the concentration of trypsin inhibitors in RFSB as an ingredient was 16 564 TIU/g, and its CP in vitro digestibility was improved significantly by protease and protease plus phytase. Birds fed on PC and on NC plus protease and phytase finally consumed higher quantities of feed and had the highest bodyweight gain (BWG). Protease improved feed intake (FI), BWG and feed conversion ratio (FCR) by approximately 5.3%, 22.5% and 11.4%, respectively, in phase 2. Birds on the diet with protease plus phytase were 11.7% and 24.8% superior in BWG and FCR, respectively, to NC between 26 and 31 days. Supplementation with both enzymes reduced the weight of the pancreas. Supplementing NC with protease and phytase marginally improved the apparent ileal digestibility (AID) of protein and some amino acids (AA) at 25 and 31 days. Overall, BWG and feed efficiency of birds were improved by supplementation of both enzymes and, to a lesser extent, by protease on its own. Keywords: anti-nutritional factors, ileal digestibility, pancreas, trypsin inhibitors, sole source crude protein and amino acids
Highlights
Soybean meal (SBM) is the most important and preferred source of quality protein in animal feeds (Banaszkiewicz, 2011)
When the commercial soybean meal (SBM) was replaced with raw full-fat soybean (RFSB) at 25% (75 g/kg diet), the concentration of trypsin inhibitors (TI) was increased by about fivefold (NC)
These results suggest synergistic and combined effects of the two enzymes on anti-nutritional factors (ANFs)
Summary
Soybean meal (SBM) is the most important and preferred source of quality protein in animal feeds (Banaszkiewicz, 2011). SBM contains the highest crude protein (CP) and has the best AA profile, with only 6% crude fibre (Dei, 2011). The AAs in SBM are highly digestible by poultry (Newkirk, 2010). Based on the CP content, SBM can generally be classified as high protein (47% - 50%), or low protein (44% - 46%). Untreated soybeans contain several anti-nutritional factors (ANFs), including trypsin inhibitors, lectins and phytate (Liu, 1998; Newkirk, 2010). Trypsin inhibitors and lectins inhibit protease and other enzymes in the digestive tract, the activity of trypsin and chymotrypsin, and contribute to reducing protein digestion in non-ruminant animals and young ruminants (Leiner, 1994)
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