Study On The Precision, Variation And Additivity For Determining The Metabolizable Energy Of Duck Feedstuffs Using Bionic Digestion System (SDS-Ⅰ)

Four experiments were conducted to study the control accuracy of enzymatic reaction of bionic digestive system, the repeatability and precision for measuring the metabolizable energy of duck feedstuffs, the additivity of the results of metabolizable energy of four duck feedstuffs.The first part set up the parameters for controlling the accuracy of enzymatic reaction in three sets of the bionic digestive system. The results showed that the variation of temperature, flow rate of buffer, rotational speed were controlled within 2%, power 0.52KW, continuous operation time longer than 120 h when the bionic digestive system was oprated in 18～24℃. The system needed to be preheated 1.5 h before measuring.The second part was mainly on the variation of the values of dry matter digestibility and metabolizable energy of duck feedstuff using bionic digestive system. The results showed that the variation coefficients of within-batch, between-batch, total of in vitro dry matter digestibility and metabolizable energy of corn, soybean meal, cottonseed meal and wheat bran by the same bionic digestive system were all less than 1.4%, and the variation coefficients of within-equipment, between-equipment and total of these three bionic digestive systems were all less than 1.64%. The normality test and 95% confidence interval of in vitro dry matter digestibility and metabolizable energy in the 4 duck feedstuffs showed that the maximum absolute bias of repeated measures were 0.94 %,1.00%,1.02%,0.88% in dry matter digestibility and 0.18 MJ/kg,0.29 MJ/kg,0.18 MJ/kg,0.24 MJ/kg in metabolizable energy of corn, soybean meal, cottonseed meal and wheat bran, respectively. In repeated determinations, the maximum absolute bias of 85% data were lower than 0.75% in in vitro dry matter digestibility and lower than 0.22 MJ/kg in in vitro metabolizable energy. The results indicated that the system can be used to determinate effective energy of duck feedstuffs convenientlyrapidly and precisely.The third part aimed to obtain the best operating condition of the bionic digestive system. The potential interfering factors including particle size, washing time of digestion and reserve time of dialysis bagwere studied. The results showed there were significant difference in the dry matter digestibility and metabolizable energy values of duck feedstuffs with different particle sizes (P<0.05), and 60 screen mesh was the optimal crush size. Dry matter digestibility and metabolizable energy values of corn and soybean meal increased gradually with the increasing washing time and stabilized at last. Washing 6 times was the optimal frequency. No significant effect was found with dialysis bags at 4℃in 90 days on the dry matter digestibility and metabolizable energy of corn and soybean meal.The fourth part was on the additivity of determined metabolizable energy values of corn, soybean meal, cottonseed meal, and wheat bran by bionic digestive system. The 4 duck feedstuffs were formulated in diets with different percentages. The difference between the measured values and calculated ones were less than 0.20 MJ/kg. The results showed that the metabolizable energy of duck feedstuffs were additive.