Study On Digestible Methionine And Lysine Requirement Of Cherry Valley Ducks

Two experiments were conducted to study the effect of dietary digestible methionine (DMet) and lysine(DLys) on the growth performance,carcass traits and nitrogen emission of Cherry Valley Ducks,aiming at combining with the specific feed resources of HuBei province in China and determining the optimum DMet and DLys levels in the duck diets under the present raising conditions.In experiment 1,320 Cherry Valley Ducks were randomly assigned to 1 of 4 dietary treatment groups with eight replicates of ten ducks according to initial weight. Supplemental amino acids were added to meet essential amino acid levels of diet(with the exception of Met).The DMet levels fed were:0.32,0.38,0.44 and 0.50%(0～14d), respectively;0.28,0.31,0.34,and 0.37%(15～42d),respectively.In fact,the ratio of Met and Lys were:33:100,40:100,46:100 and 52:100(0～14d),respectively;37:100,41: 100,45:100,and 49:100(15～42d),respectively.After the final weighing at 42 d of age, eight ducklings with body weight close to pen average were selected randomly from each treatment group,individually tagged and slaughtered after 12 hours fasting for carcass characteristics.The results of experiment 1 were as follows:(1) Body weight was significantly affected by gradient DMet levels to the dose-response diet(P＜0.05).Body weight(y,g) depending on dietary DMet concentration(x,%) were described by y=-4794.2x²+3955.3x-425.86,R²=0.9474, P=0.089(on the 14th day) and y=-62155x²+39721x-3817.3,R²=0.8433,P=0.096(on the 42th day),respectively.According to this model,the DMet requirement for obtaining the fastest growth rate was 0.413%(0～14d) and 0.325%(15～35d),respectively.That was equal to the ratio 43:100 of Met to Lys.Excess dietary Met could go against growth of ducks and reduce feed conversion.(2) The experimental results showed that addition of Met in duck diets has reduced abdominal fat percentage by 33.3%(P=0.0706) and subcutaneous fat percentage by 21.6%(P=0.0512).(3) Economic benefit was significantly affected by gradient DMet levels to the dose-response diet(P＜0.05).The economic benefit(y,ï¿¥/kg) depending on the dietary DMet concentration(x,%) were described by y=16.748x²-13.735x+5.9861,R²=0.9137, P=0.073(0～14d) and y=69.163x² -43.7x+11.178,R²=0.9622,P=0.094(15～42d), respectively.According to this model,the DMet requirement for obtaining maximum economic benefit was 0.410%(0～14d) and 0.317(15～35d),respectively.In experiment 2,320 Cherry Valley Ducks were allotted on the basis of body weight to five treatments with eight replications of eight ducks each in a completely randomized design.Supplemental amino acids were added back to the diet(with the exception of Lys) to meet essential amino acid requirements.The dietary DLys levels were:0.80,0.88,0.96, 1.04 and 1.12%(0～14d),respectively;0.60,0.68,0.76,0.84 and 0.92%(14～35d), respectively.After the final weighing at 35d of age,eight ducklings with body weight close to pen average were selected randomly from each treatment group,individually tagged and slaughtered after 12 hours fasting for carcass characteristics.At 35d of age a total of 40 male Cherry Valley Ducks with similar pen weight distributed among 40 wire battery cages(1 in each pen) and fed the experimental diets with 0.3%chromic oxide (Cr₂O₃) for 7 days.The first 3d of the balance trial was an adjustment period and the following 4d was for sample collection.Excreta were collected in vinyl disc placed under wire battery floor.10ml Hydrochloric Acid were added into 100g fresh manure to avoid ammonia nitrogen loss.The manure after drying was made into air dry samples and then stored at-20℃until analyzing for nitrogen content.The results of experiment 2 were as follows:(1) Body weight and feed/gain were significantly improved by gradient DLys levels to the dose-response diet(P＜0.05).Body weight(y,g) depending on dietary DLys concentration(x,%) were described by y=-866.4x²+1641.9x-384.81,R²=0.913,P=0.087 (on the 14th day) and y=-4308.7x²+6510.5x-458.86,R²=0.9177,P=0.082(on the 35th day),respectively.According to this model,the DLys requirement for obtaining the fastest growth rate was 0.948%(0～14d) and 0.756%(15～35d),respectively.The feed/gain(y) depending on dietary DLys concentration(x,%) were described by y=5.4281x² -10.815x+6.8803,R²=0.9709,P=0.029(0～14d) and y=5.8488x²-9.2696x +6.0233, R²=0.9173,P=0.083(14～35d),respectively.According to this model,the DLys requirement for obtaining minimum ratio of feed to gain was 0.996%(0～14d) and 0.792%(15～35d),respectively. (2) The different DLys levels in duck diets have significantly improved carcass composition and reduced fat depsition(P＜0.05).The breast meat yield(y,%) depending on the dietary DLys concentration(x,%) were described by y=-34.716x² +66.711x-24.256,R²=0.8918,P=0.110(0～14d) and y=-34.716x²+52.825x-12.303, R²=0.8918,P=0.110(15～35d),respectively.According to this model,the DLys requirement for obtaining maximum breast meat yield was 0.961%(0～14d) and 0.761% (15～35d),respectively.The subcutaneous fat percentage was significantly decreased with the incremental levels of the dietary DLys,following a linear trend,which were described by y=-9.8867x+39.855,R²=0.8703,P=0.068(0～14d);y=-9.8867x+37.878,R²=0.8703, P=0.068(15～35d).(3) In the balance trial,the different DLys levels in duck diets have significantly reduced N excretion and improved N availability for 35-day-old Ducks(P＜0.05).The N excretion(y,%) depending on the dietary DLys concentration(x,%) was described by y=100.85x²-153.17x+92.279,R²=0.9007,P=0.103.The N availability(y,%) depending on the dietary DLys concentration(x,%) was described by y=-153.81x²+234.7x+39.438, R²=0.9161,P=0.083.According to this model,the DLys requirement for obtaining minimum N excretion and maximum N availability was 0.760%and 0.763%, respectively.(4) The different DLys levels in duck diets have a significantly improved economic benefit(P＜0.05).The economic benefit(y,ï¿¥/kg) depending on the dietary DLys concentration(x,%) was described by y=16.533x²-31.658x+18.978,R²=0.8747,P=0.062 (0～14d) and y=14.125x²-21.429x+13.092,R²=0.928,P=0.046(15～35d),respectively. According to this model,the DLys requirement for obtaining maximum economic benefit was 0.957%(0～14d) and 0.755(15～35d).From the results all above,the conclusions are as follows:(1) The different DMet levels in duck diets have improved growth performance, increased breast muscle rate and reduced fat deposition.The DMet requirement for obtaining the fastest growth rate was 0.413%(0～14d) and 0.325%(15～35d),respectively. That was equal to the ratio 43:100 of Met to Lys.Excess dietary Met could go against growth of ducks and reduce feed conversion and breast meat yield. (2) The different DLys levels in duck diets have significantly effect improved growth performance,increased breast muscle rate and reduced fat deposition.The DLys level was quite different due to different production goal.The optimum DLys requirement based on the optimal feed efficiency(0～14d:0.996%;15-35d:0.792%) was higher than the optimum body weight(0～14d:0.948%;15～35d:0.756%),breast meat yield(0～14d: 0.961%;15～35d:0.761%) and subcutaneous fat percentage for ducks.And the DLys requirement for body weight is the lowest.In present study,the digestible Lys requirement for minimum N excretion was 0.760%for duck(15～35d).