An experiment was conducted to explore the effects of digestible amino acid(dAA)concentrations and supplemental protease on live performance and energy partitioning in broilers.Ross 308 male broilers(n=288)were distributed into 24 floor pens and offered 1 of 4 dietary treatments with 6 replicates from 1 to 35 d of age.Dietary treatments consisted of a 2×2 factorial arrangement with dAA concentrations(standard and reduced[34 g/kg below standard])and supplemental protease(without or with)as the main factors.At 1,15,28,and 35 d of age,feed and broilers were weighed to determine live performance.From 20 to 23 d of age,a total of 32 birds(2 birds/chamber,4 replicates)were placed in closed-calorimeter chambers to determine respiratory exchange(heat production,HP),apparent metabolisable energy(AME),retained energy(RE),and net energy(NE).From 29 to 35 d of age,supplemental protease in the reduced-dAA diet decreased broiler feed conversion ratio(FCR)by 5.6 points,whereas protease supplementation in the standard-dAA diet increased FCR by 5.8 points.The indirect calorimetry assay revealed that supplemental protease decreased(P＜0.05)the heat increment of feed(HIF)by 0.22 MJ/kg.Also,from 20 to 23 d of age,broilers offered the reduced-dAA diet with supplemental protease had a higher daily body weight gain(BWG)(+10.4％),N intake(+7.1％),and N retention(+8.2％)than those offered the standard-dAA with supplemental protease.Broilers offered the reduced-dAA without supplemental protease exhibited a 3.6％higher AME-to-crude protein(CP)ratio than those offered other treatments.Protease supplementation in the standard-and reduced-dAA diets resulted in 2.7％and 5.6％lower AME intake-to-N retention ratios,respectively,compared with the unsupplemented controls.Reduced-dAA increased(P＜0.05)AME intake(+4.8％),RE(+9.8％),NE intake(+5.8％),NE intake-to-CP ratio(+3.0％),and RE fat-to-RE ratio(+8.6％).Protease supplementation increased(P＜0.05)respiratory quotient(+1.2％)and N retention-to-N intake ratio(+2.2％),NE-to-AME ratio(+1.9％),and reduced HP(-3.6％),heat increment(-7.4％),and NE intake-to-N retention(-2.5％).In conclusion,protease positively affected FCR and energy partitioning in broilers;responses were most apparent in diets with reduced-dAA concentrations.

Klint W.McCafferty;Mingan Choct;Sosthene Musigwa;Natalie K.Morgan;Aaron J.Cowieson;Amy F.Moss

USDA-ARS Poultry Research Unit,School of Environmental and Rural Sciences,Mississippi State,39762,United States;University of New England,Armidale,NSW,2351,Australia;DSM Nutritional Products,Kaiseraugst,4303,Switzerland

动物营养（英文）

[1]Klint W.McCafferty;Mingan Choct;Sosthene Musigwa;Natalie K.Morgan;Aaron J.Cowieson;Amy F.Moss-.Protease supplementation reduced the heat increment of feed and improved energy and nitrogen partitioning in broilers fed maize-based diets with supplemental phytase and xylanase)[J].动物营养（英文）,2022(03):19-25

phytase,dAA,metabolisable,BWG,Broilers,unsupplemented

Protease,supplementation,reduced,heat,increment,feed,improved,energy,nitrogen,partitioning,broilers,fed,maize,diets,supplemental,xylanase,An,experiment,was,conducted,explore,effects,digestible,amino,acid,concentrations,protease,live,performance,Ross,male,were,distributed,into,floor,pens,offered,dietary,treatments,replicates,from,age,Dietary,consisted,factorial,arrangement,standard,below,without,main,factors,At,weighed,determine,From,total,birds,placed,closed,calorimeter,chambers,respiratory,exchange,production,HP,apparent,AME,retained,RE,net,NE,decreased,conversion,FCR,by,points,whereas,increased,indirect,calorimetry,assay,revealed,that,HIF,MJ,Also,had,higher,daily,body,weight,gain,+10,intake,+7,retention,+8,than,those,exhibited,crude,protein,CP,other,resulted,lower,ratios,respectively,compared,controls,Reduced,+4,+9,+5,+3,fat,quotient,+2,In,conclusion,positively,affected,responses,most

0.389902