| Three experiments were conducted to investigated the regressive relationship between total mixed ration (TMR) and the production performance of fattening lamb, forage utilization and dressing rate of fattened lamb, in order to formulate optimal ration.In experiment I (feeding experiment) a design of guardratic rotation regression was used to study the effect of nine kinds of TMR on the production performance of fattening lambs with forty male crossbreed (Texel X local breed) lambs, which were randomly divided into 9 dietary treatments, including 8 with 4 lambs each group and 1 with 8 lambs. All nine kinds of TMR containing different proportion of corn straw, mixed concentration and alfalfa powder were pelleted. Lambs were free choice fed individually .The finishing stage was 60 days. Daily feed intake (DFI)and daily gain (DG)were measured .The cost of feed (CF)for fattened lambs were calculated.In experiment II ,after feeding experiment the digestion experiment was conducted according to the same design as experiment I .Apparent nutrient digestibility of each group were determined by means of all feces collection, including DMD.. OMD~ CPDNDFD and ADFD.In experiment III two fattened lambs of every group from 1st to 8th ,weighting approximately the mean value of each group, were selected to slaughter .All of the 9th group were slaughtered. The regressive relationship between the different TMR and the dressing rate (DR) was set up.The results showed:I .There were negative associative effect of corn straw and mixed concentration on DO feed efficiency(FE) ~CF~ DM1)~ NDFD~ ADFD~ OMD and DR .There were active associative effect of corn straw and mixed concentration on DFI and CPD.2.There were negative associative effect of alfalfa and mixed concentration on DFI. DMD~ CPD~ NDFD and ADFD. There were active associative effect of alfalfa and mixed concentration on DG~ FE~ CF~ OMD and DR.3 .There were negative associative effect of corn straw and alfalfa on DO~ FE ~. CFOMD and DR. There were active associative effect of corn straw and alfalfa on DFI..DMI)~ CPD~ NDFD and ADFD.4.The regression equation of TMR formula composition on performance was as follows:Y, IndexZ1, proportion of corn straw in TMR,0.20~Z1~0.58,Z2, proportion of mixed concentration in TMR,0.26 ~ Z2 ~ 0.66,Z3, proportion of alfalfa in TMR,0.01 ~Z3~0.32Y(DG,g)200.03+98.49 Z12+98.49 Z,2-60.32 Z32-66.46 Z14-66.46 Z2-45.22 Z3 -196.99 Z,Z2+259.36 Z2Z3-259.3Z,Z3Y(DFI,g)?1292.06 ?13.87Z,?513.87 Z~-2O84.42 Zo~-458.50 Z1+4S8.50 Z.2 +1232.31Z,+!027 75Z,Zr823 94 Z,Z,+823.94 Z,Z0Y(FE,glg)=6.56 ?.48Z12-I.48 Z22-4.30 Z32+O.14 Z1-O.14 Z2+7.06 Z3+2.96Z1Z2-19.43 Z2Z3+19.43 Z1Z3Attending the maximum DG, the optimal formula is corn straw 19.65%, mixed concentration 53.5 1%, alfalfa 26.83%. The ratio of concentration to forage was 54:46, the expected DG would be 241g. Attending the maximum DFI, the optimal formula is corn straw 25.25%, mixed concentration 50.06%, alfalfa 24.69%. The ratio of concentration to forage was 50:50, the expected DFI would-be 1500g. Attending the highest FE, the optimal formula is corn straw 19.03%, mixed concentration 52.83%, alfalfa 28.1 4%.The ratio of concentration to forage was 53 :47,the highest FE would be 6.14:1.5.The regression equation of TMR formula composition on CF was as follows:Y (CF,Y/kgWG) 3.79-2.19Zi2-2.19Z~-5.2OZ32-3.14Z1+3.14Z2+6.47Z3+4.3sz1z2~Io.2sz2z3+1o.2sZ1z3(F1< F0.01. F2>F001)Attending the lowest CF, the optimal formula is corn straw 58.97%,mixed concentration 39.1 7%,alfalfa I .86%.The ratio of concentration to forage was 39:61 ,the lowest CF would be 3.24Y/kg wg.6.The regression equations of TMR formula composition on apparent nutrient digestibility were as follows:V (DMD%)?6.96+45.97Z12+45.97Z~2+99.64Z32-6.86 Z1+6.86 Zr14.86 Z3-91.94Z,Z2-O.78Z2Z~+O.78Z1Z3V (OMD%)?9.O8+4L29Z12+41.29Z22+79.08Z32-7.74Z1+7.74 Z2-1O.74 Z3-82.58Z1Z2+2.ISZ.Z3-2.18Z1Z3V (CPD%)?1.15-92.99Z12~92.99Z22~345.92Z3k65.81Z1+65jtZ2+t58.76 Z3+185.98Z1Z2-219.96Z2ZG+219.9...
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