| Corn distillers dried grains with solubles（DDGS）is a by-product of corn fuel ethanol production.In this study,two feeding experiments were conducted to investigate the effects of corn DDGS on laying performance,egg quality,serum biochemical indexes and dietary nutrient availability of laying ducks,in order to determine the suitable dietary level of corn DDGS in laying duck.Furthermore,the apparent matabolizable energy and energy utilization of corn DDGS was evaluated through the metabolism experiment in laying ducks.The results would provide data to support the replacement of corn and soybean meal,and the application of corn DDGS in laying duck diet.Experiment 1:Effect of dietary DDGS level on laying performance,egg quality,serum biochemistry and nutrient availability of 50-62 week-old laying ducks.The purpose of this experiment was to study the suitable dietary level of dietary DDGS（CP 25.57.%）in laying duck at 50 to 62 weeks of age.A single factor randomized trial design was used,with DDGS levels were 0%,6%,12%,18%and 24%,respectively.All the diets were formulated based on isonitrogenous and isocaloric with same digestible lysine,methionine,tryptophan and threonine.A total of 600 healthy 50-week-old Jinding ducks with similar laying performance were randomly allocated to 5 treatments with 10replicates per treatment and 12 ducks per replicate.The experiment lasted for 12 weeks and the ducks were allowed to diet and water freely throughout the experiment.The results showed as follows:Dietary DDGS levels had no significant effect on the hen-housed laying rate,hen-day laying rate,average egg weight,average daily feed intake,feed to egg ratio and mortality of laying ducks（P>0.05）.With the increasing of dietary DDGS levels,a linear increase was observed in the yolk colour and eggshell percentage at week 8（P<0.05）,while eggshell strength and eggshell thickness showed a quadratic effect of first decreasing and then increasing（P<0.05）.At week 12,the yolk color and albumen percentage showed a linear increase（P<0.05）,and the yolk percentage showed a linear decrease（P<0.05）.Triglyceride（TG）and low-density lipoprotein cholesterol（LDL-C）concentrations in ducks were increased linearly with the increasing levels of dietary DDGS（P<0.05）.With the increasing of dietary DDGS levels,a linear decrease was observed in the utilization of dry matter（DM）,crude protein（CP）and energy（P<0.05）,and the utilization of ether extract presented a linear increase（P<0.05）.Compared to the 0%and 6%DDGS groups,the utilization of dietary threonine（Thr）,isoleucine（Ile）,histidine（His）,aspartic acid（Asp）,tyrosine（Tyr）,serine（Ser）and proline（Pro）in 12%,18%and 24%DDGS groups were significantly decreased（P<0.05）.In conclusion,the dietary level of corn DDGS in laying duck at 50-62 week old could reach 24%without negative effects on the egg production performance,but the suitable level of corn DDGS may be 6%based on the dietary nutrient utilization.Experiment 2:Effect of dietary DDGS level on laying performance,egg quality,serum biochemistry,digestive enzyme activity and nutrient utilization of 32-43 week old laying ducksThe purpose of this experiment was to determine the level of DDGS（CP 27.51%）in laying ducks at 32 to 43 weeks of age by investigating the effects of dietary DDGS level on laying performance,egg quality,blood biochemical indexes,intestinal enzyme activity and nutrient utilization.A total of 384 healthy 32-week-old Jinding laying ducks with similar laying performance were randomly divided into 4 treatments with 8 replicates per treatment and 12 ducks per replicate.All the diets were formulated based on isonitrogenous and isocaloric with same digestible lysine,methionine,tryptophan and threonine.The corn DDGS level was 0%,6%,12%and 24%,respectively.The experiment lasted for 12 weeks and the ducks were allowed to diet and water freely throughout the experiment.The results showed that:Compared with other groups,the 24%corn DDGS group had a significantly increased feed to egg ratio（P<0.05）,significantly decreased average egg weight and average daily egg weight（P<0.05）for the whole trial period,and significantly decreased hen-housed laying rate,hen-day laying rate and hen-housed average egg number from 1 to 4 weeks（P<0.05）.The yolk color at weeks 4,8 and 12 increased linearly with increasing DDGS levels（P<0.05）.Globulin（GLB）,total cholesterol（TC）and LDL-C contents first decreased and then increased with increasing levels of DDGS in the diet（P<0.05）in62-week-old ducks.As DDGS levels increased,the jejunal lipase and chymase activities increased linearly（P<0.05）,α-amylase activity decreased and then increased（P<0.05）,and trypsin activity increased and then decreased（P<0.05）.As the level of DDGS increased,the utilization of DM,energy,CP,Thr,methionine（Met）,His,arginine（Arg）,Asp and total amino acids decreased linearly（P<0.05）and there was a linear decrease in the apparent utilization of essential amino acids（EAA）in ducks（P=0.055）.The profit of12%DDGS group was higher than the control group,and the profit of 6%and 24%DDGS groups were lower than the control group in the whole trial period.Considering the results of laying performance,egg quality,serum biochemical indexes,intestinal digestive enzyme activity,dietary nutrients utilization and economic benefits,the suitable level of corn DDGS in laying duck at 32-43 week old may be 12%.Experiment 3:Study on the metabolic energy of corn DDGS in laying ducksIn this experiment,the metabolic energy values and energy utilization of the two corn DDGS in experiment 1 and experiment 2 for laying ducks were evaluated.Thirty-two healthy,46-week-old Jinding ducks with similar egg production were divided into three groups,including one basal diet group and two corn DDGS replacement groups.Each group consisted of eight replicates,with two ducks in each replicate.The metabolic test was conducted by using DDGS to replace the basal diet at 20%`with 0.5%Ti O2 as exogenous indicator,and the excreta were collected after feeding experiment diets for 3days.The results showed that:The experimental 1 DDGS showed 83.58%,13.53 and 11.44 MJ/kg of energy utilization,apparent metabolic energy（AME）and nitrogen corrected apparent metabolizable energy（AMEn）for laying ducks,respectively;and the experimental 2DDGS showed 71.56%,12.00 and 8.71 MJ/kg of energy utilization,AME and AMEn for ducks,respectively,while the energy utilization,AME and AMEn of this DDGS were significantly lower than that of test 1 DDGS（P<0.05）.In conclusion,the dietary level of DDGS（CP 25.57%）in the laying duck at 50-62weeks could reach 24%,while the suitable level is 6%;the suitable dietary level of DDGS（CP 27.51%）in the laying duck at 32-43 weeks is 12%;the apparent metabolic energy of two kinds of corn DDGS for ducks is 13.53 and 12.00 MJ/kg,and the apparent metabolic energy of nitrogen correction is 11.44 and 8.71 MJ/kg,respectively. |
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