| The scientific evaluation technology on nutrient values of feeds is the basis of formulating high quality and efficient compound feeds for ducks.Bioavailable energy of duck feeds is generally measured by apparent metabolizable energy(AME)and true metabolizable energy(TME).However,there’s larger variation about AME and TME determinations and around 10% at most,which are labor-intensive,time-consuming and costly.Therefore,it is of extreme significance to study the techniques and methods for the accurate and rapid evaluation of duck feed ingredients to scientifically formulate duck feeds and improve the utilization.Based on different feed ingredients and mixed diets,four experiments were conducted to evaluate the energy efficiency and the feasibility of formulating duck feeds with enzymolysis method.The first experiment was to measure the general nutrient components(GNC)and enzyme hydrolysate gross energy(EHGE)of different feed ingredients and analyze their correlation.The GNC included crude protein(CP),ether extract(EE),crude fiber(CF),ash(Ash)and nitrogen-free extract(NFE).The results showed that the GNC of 16 corn were weakly correlated with EHGE(∣r∣<0.3);CP of 11 soybean meal was significantly and positively correlated with EHGE(r=0.622),but there was significantly negative correlation between EE or CF and EHGE(r=-0.672,r=-0.708).EE of 11 corn DDGS was remarkably and positively correlated with EHGE(r=0.769),but others were all negatively associated with EHGE(∣r∣<0.6);CF of 6 peanut meal was significantly and negatively correlated with EHGE(r=-0.95),and others were moderately correlated with EHGE,respectively(∣r∣<0.5);CP,EE and NFE of 7 rice bran were positively correlated with EHGE(r<0.5),but others were negatively correlated with EHGE(∣r∣<0.53);NFE of 6 corn gluten meal was positively correlated with EHGE(r=0.267),but others were negatively correlated with EHGE(∣r∣<0.6).CF and NFE of 5 flour were negatively correlated with EHGE(∣r∣<0.53),others showed a positive correlation with EHGE(r<0.71).Analyzing all feedstuffs’ GNC and EHGE,we could find there were significantly negative correlation between EE,CF,Ash and EHGE(r=-0.584,r=-0.812,r=-0.732),others were positively correlated with EHGE(r<0.25),which was different from the correlation of single feedstuffs.The results above show that there are different correlation between GNC and EHGE of feedstuffs,and it will be more targeted to analyze the correlation with a single feedstuff.The second experiment was to investigate the correlation between EHGE and AME or TME of different feed ingredients and mixed diets with various proportions and gradients and establish mathematical regression models.The corn and corn gluten meal,soybean meal and wheat bran were,respectively,prepared as high energy group and low energy group and formulated into 6 mixed diets(A)with CP 20%;Soybean hulls and peeled soybean meal were mixed into 5 soybean meal(C)with CP36%,38%,40%,42% and 44%,respectively,and then combined with corn starch to formulate 5 mixed diets(B)with CP 20%;5 representative corn DDGS(E)and corn starch were formulated into 5 mixed diets(D)with CP 20%.The results showed that there were significantly linear positive correlationsbetween EHGE and AME of TME of mixed diets(A)(r=0.998,P<0.0001;r=0.997,P<0.0001);For mixed diet(B),there were significantly linear positive correlations between EHGE and AME of TME(r=0.967,P=0.0071;r=0.978,P=0.042);For 5 formulated soybean meal(C),there were significantly linear positive correlations between EHGE and AME of TME(r=0.956,P=0.011;r=0.968,P=0.007);For mixed diets(D),there were significantly linear positive correlations between EHGE and AME of TME(r=0.998,P<0.0001;r=0.999,P<0.0001);For representative corn DDGS(E),there were significantly linear positive correlations between EHGE and AME of TME(r=0.995,P=0.0004;r=0.996,P=0.0003).The results above indicate that there are significantly positive linear correlations between EHGE and AME or TME of feedstuffs and mixed diets for ducks,and EHGE can be predicted by ME by establishing regression model.The third experiment was designed to study the additivity of EHGE on the basis of mixed diets with different proportions and gradients.In addition to the mixed diets in experiment 2,mixed diets(F)formulated by corn,soybean meal and wheat bran(40:30:30,50:25:25,60:20:20,70:15:15,80:10: 10),mixed diets(G)formulated by corn,soybean meal and wheat bran from different origins(40:30:30,50:25:25,60:20:20,70:15:15,80:10:10),mixed diets(H)formulated by corn,corn gluten meal and wheat bran(40:30:30,50:25:25,60:20:20,70:15:15,80:10:10).According to t test,we found there was insignificant difference between real and calculated EHGE of 5 formulated soybean meal(C)(P=0.696);For mixed diets(B),the difference between real and calculated EHGE was significant(P<0.0001);For diets(D),real and calculated EHGE was remarkably different(P=0.03);For diet(F),there was significant difference between real and calculated EHGE(P=0.011);For diet(G),real and calculated EHGE wasn’t significantly different(P=0.093);For diets(H),real and calculated EHGE wasn’t significantly different(P=0.227);For diets(A),there was extremely significant difference between real and calculated EHGE(P<0.0005).So EHGE of mixed diets can be additive,but the additivity could be down with increasing feedstuffs and certain variation could turn out in terms of different types and mixed diets formulated by same materials but from different origins.The fourth experiment was to investigate the requirement of EHGE for starter ducks.Six EHGE levels of mixed diets with 2600,2720,2840,2960,3080,3200 kcal/kg were arranged,8 duplicates per level and 8 1-day male ducks per duplicate.The results indicated that the optimal EHGE requirement for ducks of 0~14 and 0~21 days old were 2850,2937 kcal/kg(87% DM)based on corresponding average body weight(ABW)and average daily gain(ADG)with the broken line model.Considering real EHGE and ABW,the real and optimal EHGE requirement of 0~14 and 0~21 days old were 3095 and 3182 kcal/kg(real 91% DM),respectively. |
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