| With the need of animal husbandry development, serious shortage in the raw materials of protein feed occurs in our country. The double low rapeseed meal as by-products of oil processing has high protein content and its amino acid composition is complete and rich, and has been exploited as important protein raw materials, but it contains massive amount of anti-nutrients which limit the supplementation in animal feed. Extrusion expansion technique has the characteristics of lowering material anti-nutrients and improving the utilization ratio of nutrient, thus has received increasing attention.The present study uses TSE65 type twin-screw extruder to process the double low rapeseed meal to reduce the anti-nutrients contents and improve the bioavailability of nutrients. Based on series of extrusion and poultry feeding experiments, the results obtained are shown as follows:(1) Double low rapeseed meal as raw material, fixing the rotational speed of host screw, feed rate, die hole size and other factors, the moisture content of rapeseed meal was adjusted to conduct a single factor experiment to investigate the changes in nutrient and anti-nutrient contents. The results showed that with the increase of the moisture content of double low rapeseed meal, protein solubility and total amino acid content increased, protein digestion rate in vitro increased early and then reduced, tannins and sinapine contents decreased along with the change in moisture content which was not significant(P > 0.05), and isothiocyanates and oxazolidine thione were destroyed after extrusion processing.(2) Double low rapeseed meal as raw material, expansion chamber temperature, the moisture content of rapeseed meal and the screw speed as test factors, effects on tannins content, neutral detergent fiber content and protein digestibility in vitro were evaluated by the three factors, four levels orthogonal experiment. The optimum technique conditions are 150 ℃ of barrel temperature in the last zone, 16.10% of the moisture content, and 210 r/min of the screw speed, which was validated.(3) The 200 type of and mixed type of double low rapeseed meal were extruded under the optimal processing parameters, respectively. Since having brown fine powder, the mixed type of double low rapeseed meal could not be extruded in actual operation under 16.10% of low moisture content. Thus, the moisture content increased to 22.99% for extrusion expansion. It was shown that glucosinolate and sinapine contents in the 200 type of double low rapeseed meal decreased significantly after extruding(P <0.05), however, the contents of tannins, neutral detergent fiber and acid detergent fiber reduced but the changes were not significant(P > 0.05). The contents of glucosinolate, sinapine, tannins, neutral detergent fiber and acid detergent fiber in the mixed type of double low rapeseed meal were significantly decreased(P < 0.05), but the protein solubility were also significantly reduced(P < 0.05).(4) The extruded double low rapeseed meal was produced under the optimal processing conditions. Different levels of the extruded double low rapeseed meal(5%, 10%, 15%, 10%) were added into the corn-soybean meal type diet, the same levels of unextruded double low rapeseed meal used as control. The broiler growth performance, biochemical indexes, and the organ body ratio were compared through the broilers feeding experiment and observation of the thyroid pathological tissue slice. The results showed that extrusion processing could improve the feed conversion rate of the double low rapeseed meal and had more advantage of the broilers growth to unextrusion processing. But if the advantage of extrusion is made full use, it is better to consider the digestible amino acid balance in the practical formula. |
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