The effect of methods of castration on live weight, dressed percentage and linear body measurements of indigenous Tswana goats raised under semi-intensive management in Southeast Botswana

摘要

Theaimsofthisstudyweretoinvestigatetheeffectofdifferentmethodsofcastrationonbodyweight,linearbodymeasurementsanddressedpercentageofindigenousTswanagoatsraisedundersemi-intensivemanagementovertime.Thirty-two(32)maleindigenousTswanagoatsaged4monthswererandomlydividedintofourgroupsofeight,balancingforweightinsummer.Onegroupwasrandomlychosentobeacontroli.e.notcastratedandtheotherthreerandomlyallocatedtogroupswhichwereimmediatelycastratedusingburdizzo,rubberringandshortscrotumrespectively.Theinitialaverageliveweightswere12.50±1.69kg,13.75±1.69kg,12.25±1.69kgand12.00±1.69kgforcontrol,burdizzo,rubberringandshortscrotumcastratesrespectively.Thegoatsweremanagedasasinglemobtogetherwithalargegroupoffemalesundersemi-intensivesystemwithregularsupplementaryfeeding,adequatemedicalcareandwaterwasprovidedadlibitum.Allthegoatswereweighedmonthly.At12monthsofagetheshortscrotumandcontrolhadthetypicaltaintedsmell,whichwouldrenderthemeatunsuitableforhumanconsumption.At14monthsofagethreegoatswererandomlyselectedfromeachgroupandslaughteredbyexsanguinations,whiletheremaininggoatswereslaughteredat22monthsofage.DatawithunequalsubclasseswereanalysedusingGeneralLinearModelprocedure,whiledatawithequalsub-classeswereanalysedusingANOVAprocedureinStatisticalSystemAnalysis.Liveweightwasnotsignificantlyaffectedbymethodofcastration(P0.05)atthesameageandstageofdevelopment.Liveweightincreasedsteadilyinallgroupsfromaround12kgtoamaximumofapproximately29kgat22monthsofage.Thedressedpercentagesweresignificantlyhigherinburdizzo(47.86±1.37and42.07±0.88%)andrubberring(43.44±1.37and42.05±0.76%)thancontrol(42.50±1.37and36.80±0.88%)andshortscrotum(41.73±1.37and37.02±0.88%)at14and22monthsofagerespectively.Noneofthelinearmeasurementsdifferedsignificantlyat14monthsofage.However,at22monthsofage,heightatwitherswassignificantlyhigherintheburdizzo(61.00±1.26cm),shortscrotum(59.23±1.26cm)andrubberring(58.75±1.09cm)groupsthanthecontrolgroup(53.16±1.26cm).Diagonallengthalsodifferedsignificantlybetweentheburdizzo(54.50±1.59cm)andcontrol(47.33±1.59cm)groupsonly.Togetherthehigherdressingpercentage,andlongeranddeeperbodylinearmeasurementsofthegoatscastratedusingburdizzosuggeststhatfarmersshouldusethismethodofcastration.