Growth, maturity and carcase specifications
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19 2003 Armidale Feeder Steer School Growth, maturity and carcase specifications NSW Agriculture Beef Industry Centre, UNE Armidale NSW 2351 Ph: 02 6770 1812 Fax: 02 6770 1830 Email: [email protected] Bob Gaden Session 2a Introduction The aim of this session is to set a simple foundation for understanding the main principles of growth and maturity. This is the basis for deciding how to find the best combination of frame size, muscling, breed type and nutrition to meet market specifications for weight and fat depth. A general growth curve Let’s imagine Figure 2a-1 is the growth curve for a typical steer from birth to maturity, with adequate nutrition to meet his basic needs: As the animal grows from birth to maturity, there are changes in the proportion of fat, muscle and bone (Figure 2a-2). Stage 1 Stage 1 Calf Calf Growout Growout Finish Finish Age Age Weight Weight Three phases of growth Stage 2 Stage 2 Stage 3 Stage 3 Bone Bone Muscle Muscle Fat Fat Figure 2a-1. General growth curve Age Age Weight Weight Composition of growth bone bone muscle muscle fat fat Figure 2a-2. Composition of growth Stage 1 - Birth to weaning (say 6-7 months) After birth, bone growth is first priority, to establish frame for future body growth. New muscle cells are being formed and muscle weight increases rapidly. Fat is only deposited in small quantities. A calf requires nutrition of very high quality to develop bone and muscle, and this is mainly ensured by milk from its mother. Inadequate nutrition at this stage affects future development. The carcase at this stage has a high bone content, high muscle, low fat, with low gut weight. The meat from calves is tender, has little hard connective tissue, and not much flavour. Stage 2 - Growing out In mid growth (say after weaning at 6-9 months) bone growth continues but the animal’s main priority becomes muscle growth. Normally, fat is only deposited in small quantities. This is the “backgrounding” or “growing out” phase. The growing animal requires high quality protein-rich diet, and the rate of development during this phase is very sensitive to feed quality. After weaning, gut weight increases markedly to cope with digesting roughage diets – this keeps dressing percentage down. The carcase itself has an increasing ratio of muscle to bone, and very little fat, so generally has a high yield (percentage of saleable meat). Meat is tender at this vealer/yearling stage,
Transcript of Growth, maturity and carcase specifications
192003 Armidale Feeder Steer School
Growth, maturity and carcase specificationsNSW AgricultureBeef Industry Centre, UNEArmidale NSW 2351Ph: 02 6770 1812Fax: 02 6770 1830Email: [email protected]
Bob Gaden
Session 2a
IntroductionThe aim of this session is to set a simple foundation for understanding the main principles ofgrowthandmaturity.Thisisthebasisfordecidinghowtofindthebestcombinationofframesize,muscling,breedtypeandnutritiontomeetmarketspecificationsforweightandfatdepth.
A general growth curveLet’simagineFigure2a-1isthegrowthcurveforatypicalsteerfrombirthtomaturity,withadequatenutritiontomeethisbasicneeds:
Astheanimalgrowsfrombirthtomaturity,therearechangesintheproportionoffat,muscleandbone(Figure2a-2).
Stage 1Stage 1
CalfCalf
GrowoutGrowout
FinishFinish
AgeAge
WeightWeight
Three phases of growth
Stage 2Stage 2 Stage 3Stage 3
BoneBone
MuscleMuscle
FatFat
Figure 2a-1. General growth curveAgeAge
WeightWeight
Composition of growth
bonebone
musclemuscle
fatfat
Figure 2a-2. Composition of growth
Stage 1 - Birth to weaning (say 6-7 months)After birth, bone growth is first priority, toestablish frame for future body growth. Newmuscle cells are being formed and muscleweight increases rapidly.Fat is onlydepositedinsmallquantities.
A calf requires nutrition of very high qualityto develop bone and muscle, and this ismainly ensured by milk from its mother.Inadequatenutritionatthisstageaffectsfuturedevelopment.
The carcase at this stage has a high bonecontent, high muscle, low fat, with low gutweight.
Themeatfromcalves istender,has littlehardconnectivetissue,andnotmuchflavour.
Stage 2 - Growing outInmidgrowth(sayafterweaningat6-9months)bone growth continues but the animal’s mainpriority becomes muscle growth. Normally, fatisonlydepositedinsmallquantities.Thisisthe“backgrounding”or“growingout”phase.
The growing animal requires high qualityprotein-rich diet, and the rate of developmentduring this phase is very sensitive to feedquality.
After weaning, gut weight increases markedlyto cope with digesting roughage diets – thiskeeps dressing percentage down. The carcaseitselfhasanincreasingratioofmuscletobone,andverylittlefat,sogenerallyhasahighyield(percentageofsaleablemeat).
Meat is tender at this vealer/yearling stage,
20 2003 Armidale Feeder Steer School
andhasmoreflavour.Fatteranimalsgenerallyhavebettereatingquality,withlessriskofcoldshorteningandenhanced juiciness fromsmallamountsofmarbling.
Stage 3 - Finishing/maturingWhengrowthofbone is largelycompletedandallmusclecellshavebeenestablished,allthatisleftisformusclecellstofillout,andafterthat,surplusenergyisstoredasbodyfat.
Asanimalsmature,theycanexistonquitepoorqualityfeed,butiffeedqualityisgood,theycanexpresstheirmusclepotentialandaccumulatefatveryquickly.
As fattening takes place, fat is deposited inthe gut and carcase depots (subcutaneous orselvedge fat, intermuscular or seam fat, andintramuscular or marbling fat). The carcasebecomes an increasing proportion of the totalbody,sodressingpercentagerises.Theyieldofsaleablemeatinthecarcasefallsastheneedforfattrimmingrises.
Meat flavour reaches its maximum in theprime cuts of amature, finished steer, but asconnective tissue increases with age, thereis a decline in tenderness, especially in thesecondarycuts.
Cattle with different growth curvesSex
Heifers–giventhesameaccesstonutritionassteers,heifersgrowalittlelessbone,considerablylessmuscle,andputonconsiderablymorefat.They follow a “flatter” growth curve with anearlierendpointi.e.areearlier maturing.
Bulls – they grow moremuscle and bone, andare less inclined to putonfat.Theyhavealongerperiod in Stage 2 andgreateramountofmuscleinStage3–theyarelater maturing.
Frame size
Large framed cattle growtoahighermatureweightandtakealittlelongertoreachmatureweight(latermaturing).
Small framed cattle growtoalightermatureweightand get there earlier(earliermaturing).
Muscling
Heavilymuscled cattle at the same frame sizetake a little longer in Stage 2 to fill out theirmuscling, and carrymoremuscle and less fatlater in life. They are heavier, and effectivelylater maturing than average-muscled cattle ofthesameframesize.
Lightlymuscledcattlearelikeheifers,andfinishtheir muscle growth earlier and at a lighterweight,puttingthesurplusintoextrafat.
CattlethatareBOTHlargeframedANDheavilymuscled,suchasmostEuropeanbreed types,canbeverylatematuring.Thismeanstheyarevery difficult to fatten at lighter weights, andneedtobecarriedtoveryheavyweightstofinishadequately.
Maturity and market specificationsMarket specifications are mainly described intermsofage,sex,weightandfatdepth.Asmostof our target markets focus on young growingsteers,weight and fat depth are the twomainfactorstothinkabout.
It is therefore important to know what makescattleputonfatfasterorslowerastheygrow.Thiswilldeterminewhethertheyare“finished”and meet the target specifications for anyparticularmarket.
Changing the growth curve for a particular animalThere aremany factorswhich can change theactual growth path of a particular animal,and therefore arrive at different combinationsof weight and fat depth, to determine market
suitability. The mainfactorsarenutritionandgenetics.
Nutrition
Nutrition in Stage 1
Ifnutritionisbetterthanadequate, it allows fulldevelopment of potentialbone and muscle, andmay even allow somesurplus to be depositedas fat. Such calves arehighly sought after forslaughter as vealers at7-10months.Iftheyhaveadequate frame size andmuscling, they still havethe potential to grow onand mature at heavyweights.
212003 Armidale Feeder Steer School
On the other hand, severe restriction inStage 1 results in impaired bone and muscledevelopment–thesecalvesdon’tcatchupwhentheyareputongoodfeedlater,andwillproducecarcases with lighter weight, less muscle andmorefat.Bewaryofbuyinglightweightweaners(sayunder180kg)tofinish,andbeawarethatearly weaned calves requires special attentionto their nutrition, to ensure they retain theirpotential.
Nutrition in Stage 2
Cattle receiving better than their basicrequirementsforgrowthinStage2canproduceplentyofmuscleanddepositsomefat.Mostofourtablebeefqualitydomesticandexportcattleareslaughteredinthisstageoflife,around50-70% of mature weight. High quality pasture,forage crops or feedlots will provide the goodnutritionrequiredtofinishcattlewhiletheyarestillactivelygrowing.
Restriction of nutrition in Stage 2 affects thesizeofmusclefibres,butiftheyhavehadagoodstartinlifethiswillbetemporaryandreversible.On returning to good feed they will recover,expressing compensatory gain. Fat depositionwillbedelayedalittle,resultinginleaner,higheryielding carcases. These benefits are used bycattlefinisherstoenhancetheirprofit.
Nutrition in Stage 3
InStage3,cattlefinishthedevelopmentoftheirbone and muscle structure. They can gain orlose weight according to available nutrition,withthemaineffectbeingontheproportionofbodyfat.
Recovering from poor condition, they fill outtheirmusclesfirst–thishappensquicklywhentheyhavefinishedgrowing-and thenput thesurplusbackonasfat.
Maturecattleareveryeasyandquicktofinish,once relievedof theirbreeding responsibilities,provided of course that they are sound(especiallyteeth)andhealthy.
VirtuallyallsteersareslaughteredbeforeStage3, so the main cattle in this group are cullfemalesandbulls.
Genetics
Breed effects
The main breed effects on maturity andcarcasecompositioncanbeexplainedintermsof muscling and frame size. Be aware thatgeneralisingisdangerous-thereisawide(andgrowing)variationbetweenanimalswithineachbreedinframesizeandmuscling.
Somebreedsgenerallyhavelargerframesizee.g.
Charolais,Simmental.Thesearelatermaturingandfinishatheavierweights
TheBritishbreedstendtohaveamoremoderateframe size, and finish at moderate weights.SomeBritishbreedshaveincreasedtheirframesize andmature weight significantly in recentyears.
Breeds which are strong in muscling (highmuscle to bone ratio) produce higher yieldingcarcases and are often prominent in carcasecompetitions.TheLimousinisaheavilymuscledbreedwithamoderateframe-itproduceshighyielding carcases at heavy weights, while theMurrayGreyhasasmallerframe,andproduceshigh yielding carcases at more moderateweights.
Breeds which are BOTH large framed ANDheavilymuscledwillbeverylatematuring.
Selection within breeds
It is very difficult to breed to amaturity typeif you select your bulls by eye, because whatyousee-theirframe,muscleandfatness-arestrongly influenced by non-genetic aspects oftheirupbringing.
In most breeds, BREEDPLAN produces EBVswhichproducerscanuse toselectsireswhichwill fine-tune carcase yield, fatness andmusclingandmaturesize.
Final commentsMatching genetics, nutrition and marketsuitability is a three-dimensional challenge,especially as all of them are dynamic. Cattlewithmoderateframesizeandmediumtoheavymuscling are most versatile, because withreasonable nutrition they can produce high-yielding,moderncarcases,whichfitnearlyallofourmainstreammarkets.
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