Enhancing nutritive value of palm kernel expeller through physical treatments for use as poultry feed ingredient

Poultry production in Malaysia is heavily dependent on imported feed ingredients. The palm kernel expeller (PKE) is a potential feed ingredient to sustain the poultry industry. However, PKE had to be treated before it could be incorporated in poultry feed to reduce the anti-nutritive factors like indigestible mannan, lignin and broken kernel shells.. Hence, this study aimed at reducing these factors of PKE by extrusion and static cling- electrostatic separation technique to reduce the mannan and broken shells, respectively, and to produce a poultry feed containing treated PKE with a potential for commercial application. Extrusion was conducted by using a custom made co-rotating twin-screw extruder and static cling–electrostatic separation by using a simple fabricated apparatus. Response surface methodology (RSM) was used to optimize both treatments. Extrusion of PKE at optimized conditions (temperature, 178 ºC; screw speed, 100 rpm; hopper speed, 5 Hz and PKE moisture, 75%), significantly (P<0.05) reduced non-starch polysaccharides from 63.3% to 57.6%, and crude fibre from 16.7% to 13.5%, and significantly (P<0.05) increased mannose, glucose, fructose, 1,4-β-D-mannobiose; 1,4- β-D-mannotriose; 1,4-β-D-mannohexaose and 1,4-β-D-mannopentaose content. The production rate of extruded PKE (EPKE) was 180 kg/h. The static cling–electrostatic method at optimized conditions (13% PKE moisture; <1.5 mm PKE particle size and 110 g/min feed rate), reduced shells, lignin and fibre of PKE from 8.0% to 1.6%; 15.8% to 8.1% and 17.1% to 10.2%, respectively, and increased crude protein from 16.5% to 18.4%. The production rate of less-shell PKE (LSPKE) was 50 kg/h. The study on the effects of control (0% PKE), UPKE (untreated), EPKE, LSPKE and ELSPKE at 10%, 20% and 30% inclusion rates in finisher diets (d 21-42) showed that growth performance of broilers (Cobb 500) fed 10% PKE (irrespective of treatments), 20% LSPKE and ELSPKE, were comparable to control birds. At 30% PKE inclusion, broilers performance was significantly (P<0.05) reduced. Birds fed PKE diets, irrespective of treatments and inclusion levels had lower LDL and total cholesterol, and similar villi height and crypt depth compared to control. At 30% PKE inclusion level, although energy metabolism was enhanced, as indicated by the up-regulation of hexokinase I and phosphofructokinase, but broilers growth performance did not improve. The feeding trial showed that broilers fed 25% or 30% LSPKE (grower feed, d 16-24), followed by 20% LSPKE (finisher feed, d 25-35) containing feed supplements 0.02% commercial enzymes and 0.30% humic acid), had comparable FI, BWG and FCR to broilers fed commercial feeds. Broilers fed 25% or 30% UPKE (grower feed, d 16-24) followed by 20% UPKE (finisher feed, d 25-35) showed significantly higher (P<0.05) FCR compared to birds fed commercial feeds. The cost of feeds for production of birds fed LSPKE feeds (2.27-2.29 RM/kg liveweight), was lower than those fed commercial feeds (2.36 RM/kg liveweight). The study showed that physical treatments enhanced the nutritive value of PKE and feeds containing 25-30% and 20% LSPKE as grower and finisher rations, respectively, could attain broilers growth performance comparable to broilers fed commercial feeds. These diets could be potential feeds for commercial poultry production.

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