Effects Of Diet Treatment On Net Energy Utilization And Performance Of Broilers

In 2022,China’s broiler production reached 14.30 million tons,ranking the second largest in the world.Diet is an important part of broiler production,and its cost accounts for more than70%of the total cost.Proper diet treatment can effectively improve the utilization rate of diet and reduce the cost of diet,which has great significance for the precise feeding system of broiler.In this study,AA broilers were used as test animals to explore the effects of different dietary treatments on broilers during production.The experiment was divided into two parts:Experiment 1:Effects of Corn and soybean meal pulverized size on Feed Quality,Energy Metabolism and Growth Performance of broilers of different days of age.This experiment was divided into two parts,each using a single factor completely randomized experiment design.The experimental diets were divided into two groups:corn and soybean meal.The corn group was crushed by 1 mm,2mm and 3mm crushing sieve,the other large raw materials were crushed by 2mm crushing sieve,the soybean meal group was crushed by 1 mm,2mm and 3mm crushing sieve,and the other large raw materials were crushed by2mm crushing sieve.A total of 288 broilers aged 11 days and 192 broilers aged 24 days were divided into 6 groups per day.Groups 1 to 3 were used for corn grinding grain size experiment and groups 4 to 6 were used for soybean meal experiment with 8 replicates per group and 4 or 6broilers per replicate.The experiment lasted for 6 days(3 days in pre-feeding period and 3 days in test period).The results are as follows:1.1 The geometric mean particle size of corn and soybean meal increased with the increase of sieve size.The geometric mean particle size of soybean meal was higher than that of corn under the same grinding sieve.There was a linear relationship between the geometric mean particle size of corn and sieve size:y=90x+359.33(P<0.001,R~2=0.983),and the geometric mean particle size of soybean meal and sieve size:y=110x+359.00(P<0.001,R~2=0.990).The hardness of pellet feed was significantly decreased with the increase of grinding size(P<0.05).1.2 Different grinding sizes of corn and soybean meal had no significant effect on energy metabolism of chickens in metabolizable energy level.1.3 At 11 to 16 days of age,the feed intake of broilers in soybean meal group was significantly higher than that in 1mm crushing screen(P<0.05),and the feed to gain ratio of3mm crushing screen in corn and soybean meal groups was the lowest(P<0.05).The grain size of corn and soybean meal had no significant effects on average daily gain,average daily feed intake and feed to gain ratio of broilers aged 24 to 29 days.Experiment 2:Effects of adding protease in low protein diet on performance and net energy utilization of broilersThe experiment was a 2×2 factorial design,and protein levels were reduced by 1%and 2%,respectively,according to the Arbor Acres(AA)Broiler Feeding Management Manual 2019,and protease supplemental levels were 0 and 300mg/kg.The experimental diet was corn-soybean meal type.The grain size of corn and soybean meal was crushed under 3mm sieve,which was recommended by experiment I.A total of 288 one-day-old AA broilers with similar body weight were randomly divided into 4 groups with 6 replicates per group.The experiment lasted for 21 days.Respiratory calorimetry and slaughter tests were carried out at 14 and 21 days of age,respectively.The results are as follows:2.1 Reducing dietary protein had no significant effects on body weight gain feed intake and feed to gain ratio of broilers aged from 1 to 10 and 1 to 21 days.Adding enzymes significantly increased body weight gain of broilers aged 1 to 10 and 1 to 21 days(P<0.05,P<0.01)had no significant effect on feed intake to gain ratio.2.2 Decreased protein significantly increased fat deposition energy(REf)(P<0.05),NE/AME,NE/AMEn(P<0.05),but had no significant effects on other energy metabolism indexes of broilers.Adding protease can significantly reduce N excretion,but has no significant effect on other energy metabolism indexes.Crude protein level and protease interact with THP,HI,N excretion,NE/AME,NE/AMEn of broilers.2.3 Decreasing crude protein level could significantly reduce breast muscle percentage and leg muscle percentage of broilers 1 to 10 days(P<0.01),but had no significant effect on slaughter performance of broilers 1 to 21 days;The addition of enzymes had no significant effect on the slaughter performance of broilers.Protein level and protease had interaction effects on carcass rate and leg muscle rate of broilers at 1～10 days.2.4 Neither crude protein level nor protease addition had significant effects on jejunal intestinal morphology of broilers.In conclusion,for corn-soybean meal type diet,the optimal grain size of corn and soybean meal is 638,681μm.Reducing dietary crude protein level by 1-2%has no effect on growth performance of broilers,but can change the allocation of deposited energy,increase fat deposition and improve net energy use efficiency.In conclusion,the growth performance of broilers is not significantly affected by the reduction of crude protein level by 1%or 2%,and the protein level can affect net energy use efficiency and other net energy indexes.Adding enzymes can improve the growth performance of broilers.