Genetic parameters for subjective and objective wool and body traits in the Tygerhoek Merino flock
Loading...
Date
2007-12
Authors
Matebesi-Ranthimo, Puleng Agathah
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
English: Genetic evaluation systems require accurate estimates of genetic parameters. The genetic, phenotypic and environmental parameters for objectively measured wool, subjectively assessed wool and conformation traits as well as 16-month live weight were estimated for South African Merino sheep. Records of the Tygerhoek Merino resource flock were used to estimate these parameters. The database consisted of records of 4 495 animals, the progeny of 449 sires and 1 831 dams born in the period 1989 to 2004. The pedigree records used have been collected between 1969 and 2004. In this data, four lines were represented, namely a line selected on clean fleece weight, a line selected against rearing failure, a fine wool line, as well as an unselected control line. Single trait linear mixed models were used. Fixed effects that were assessed included birth status (single/multiple), sex (male/female), age of the dam in years (2-6+years), year of birth (1989-2004) selection line (1-4) and the sex*birth year interaction. Preliminary analysis showed that all the fixed effects had significant (P<0.05) effects on all the traits studied. The random effects included a combination of direct additive, maternal additive and maternal permanent environmental effects as well as the covariance between direct and maternal additive effects. The direct heritability estimates (h²a) for objectively measured traits were 0.38 for 16- month live weight (LW), 0.36 for greasy fleece weight (GFW), 0.40 for clean fleece weight (CFW), 0.65 for clean yield (CY), 0.37 for staple length (SL), 0.20 for staple strength (SS), 0.68 for fibre diameter (FD), 0.61 for coefficient of variation of fibre diameter (CVFD) and 0.61 for standard deviation of fibre diameter (SDFD). The maternal heritability estimates were 0.05 for LW, 0.09 for GFW, 0.10 for CFW and 0.05 for FD. The proportion of the total phenotypic variance due to the maternal permanent environment (c²pe) amounted to 5% for fleece weights. The correlation between direct and maternal genetic effects for LW, GFW and CFW were -0.28, -0.65 and -0.70 respectively. These results suggested that worthwhile responses to selection for objectively measured traits would result from directed selection. Estimates of h²a for subjectively assessed wool traits were 0.49 for wool quality (QUAL), 0.28 for regularity of crimp (ROC), 0.33 for wool colour (COL), 0.23 for wool oil (OIL), 0.21 staple formation (STAPL), 0.22 belly and points (BANDP), 0.50 for woolly face score (WFS), 0.15 for face cover score (FCS), and 0.45 for pigmentation (PIGM). Maternal genetic effects were significant for QUAL, ROC and COL amounting to 0.06, 0.03 and 0.07 respectively. The correlation between direct and maternal genetic effects for QUAL, ROC and COL were -0.62, -0.70 and -0.45 respectively. The h²a estimates for subjectively assessed conformation traits were 0.13 for topline (TOPL), 0.39 for total fold score (TOT), 0.15 for front quarters (FQ), 0.16 for pastern score (PS), 0.32 for hocks (HOCKS) and 0.37 for the general conformation score of the head (GEN). Among the subjectively assessed conformation traits the maternal genetic effects were significant only for PS at 0.05 while GEN was affected by c²pe at 5%. The correlation between direct and maternal genetic effects was -0.71 for PS. The improvement of subjectively assessed wool and conformation traits by selection seems possible from the results of present study. Genetic correlations (rg) among objectively assessed traits general agreed with literature values. Among the subjectively assessed traits favourable rg estimates were estimated between ROC and COL (0.31), for QUAL with ROC (0.49) and COL (0.26) and between STAPL and BANDP (0.58). The relationships between ROC and STAPL (-0.49) and for QUAL with STAPL (-0.45) and BANDP (-0.20) were unfavourable. Estimates of rg among subjective conformation traits were generally low, variable in sign and not significant. The only exceptions were rg’s between HOCKS and FQ (0.71) and of GEN and TOPL with TOT (-0.31 and -0.47 respectively). Phenotypic and environmental correlations among objective, subjective wool and conformation traits were low to moderate. Maternal relationships of respectively 0.86 and 0.19 were found between GFW and CFW and between CFW and FD. The rg of LW with subjective wool traits were not significant, with the exception of moderate and favourable rg for LW with ROC (0.20) and for LW with WFS (0.20). These results suggested that heavier sheep are likely to have more even fleeces and higher scores for WFS. The rg were favourable with COL (-0.19), STAPL (0.35) and BANDP (0.42). CFW and CY were also favourably related to COL, STAPL, BANDP and QUAL where sheep with higher fleece weights and yield had wool with higher quality and better scores for COL, STAPL as well as BANDP. SL was favourably related to COL, BANDP and WFS and negatively related to OIL. These results indicated that sheep with longer staples had better scores for COL, BANDP and WFS as well as lower scores for OIL. Among the subjective wool traits only ROC was significantly related to SS at 0.33. Moderate and unfavourable genetic correlations were estimated for FD with QUAL, ROC and FCS, where sheep with a good quality wool that have more even fleeces and softer wool covering the face had reduced FD. The corresponding relationship with STAPL and BAND were unfavourable. Genetic correlations of CVFD and SDFD with QUAL and ROC were favourable and while these traits were unfavourably related to a number with STAPL. Phenotypic and environmental relationships between objectively measured traits and subjectively assessed wool traits were low to high and variable in sign. On the genetic level LW was favourably related to all the subjectively assessed conformation traits studied. Heavier sheep were generally plainer, had better scores for GEN, HOCKS, and FQ as well as for TOPL. Estimates of rg were favourable for CY with GEN (0.25), HOCKS (0.19), TOT (-0.26) and FQ (0.18), for FD with PS (-0.16) and TOPL (-0.18), for CVFD with HOCKS (-0.17), FQ (-0.33) and TOPL (-0.25), between CFW and GEN (0.23), and between SS and FQ (0.39). The relationships of SDFD with FQ and TOPL were negative. Unfavourable correlations occurred between SS and TOT (0.25), between FD and HOCKS and FD and TOT at 0.13, for fleece weights with TOT (GFW 0.48 and CFW 0.28) and TOPL (GFW 0.34 and CFW 0.29) and between CY and TOT at -0.26. Phenotypic and environmental relationships between objectively measured traits and subjectively assessed wool traits were low to high in magnitude and variable in sign. The results showed that selection for LW and objective wool traits will thus not seriously compromise subjective wool and conformation traits. The exception is FD, CVFD and SDFD, where unfavourable genetic relationships with STAPL and BANDP were found. Furthermore, from these results, it was clear that unrestrained discrimination against wrinkles in Merino sheep would adversely affect economically important objectively measured wool traits such as SS, FD and wool weight. Selection against wrinkles should be carefully monitored to minimise the risk of animals producing reduced fleece weights with broader fibres. It is therefore, proposed that animals with excessive wrinkles be culled from the breeding stock.
Afrikaans: Genetiese evaluasie-stelsels het die akkurate beraming van genetiese parameters nodig. Genetiese, fenotipiese en omgewingsparameters vir objektiewe wol, subjektiewe wol, subjektiewe bouvorm, sowel as vir 16-maande gewig is vir Suid-Afrikaanse Merinoskape beraam. Rekords van die Tygerhoek Merino navorsingskudde, insluitende waarnemings op 4 495 diere, die nageslag van 449 vaars en 1 831 moers en gebore in die periode 1989 tot 2004, is gebruik om hierdie parameters te beraam. Die rekords wat gebruik is, is tussen 1969 en 2004 versamel. Vier lyne is in die data verteenwoordig, naamlik: ‘n lyn geselekteer op skoonvaggewig, ‘n lyn geselekteer teen grootmaakverliese, ‘n fynwollyn, sowel as ‘n ongeselekteerde kontrolelyn. Enkel-eienskap gemengede modelle is gebruik. Vaste effekte sluit die effek van geboortestatus (enkel/meerling), geslag (manlik/vroulik), ouderdom van ooi (2-6 jaar), jaar van geboorte (1989-2004), seleksielyn (1-4), en die geslag*geboortejaar interaksie in. Voorlopige ontledings het aangedui dat al die vaste invloede ‘n betekenisvolle (P<0.05) effek op al die kenmerke wat bestudeer is, gehad het. Die toevallige effekte het kombinasies van direkte additiewe, maternale additiewe en maternale permanente omgewingsinvloede sowel as die korrelasie tussen direkte en matrenale additiewe invloede ingesluit. Die direkte oorerflikheid beramings (h²a) vir objektiewe eienskappe was 0.38 vir 16- maande gewig (LW), 0.36 vir rouwol gewig (GFW), 0.40 vir skoonwolgewig (CFW), 0.65 vir skoonopbrengs (CY), 0.37 stapellengte (SL), 0.20 vir stapelsterkte (SS), 0.68 vir veseldeursnit (FD), 0.61 vir die koeffisient van variasie van veseldeursnit (CVFD) en 0.61 vir standaardafwyking van veseldeursnit (SDFD). Die maternale oorerflikheidsberamings was 0.05 vir LW, 0.09 vir GFW, 0.10 vir CFW en 0.05 vir FD. Die proporsie van die totale fenotipiese variansie as gevolg van die maternale permanente omgewing (c²pe) het 5% tot die vaggewigte bygedra. Die korrelasie tuseen die direkte en maternale genetiese effekte vir LW, GFW en CFW was -0.28, -0.65 en -0.70 onderskeidelik. Hierdie resultate wys dat ‘n response op seleksie vir objektief gemete eienskappe hoogs waarskynlik is. Skattings vir h²a vir subjektiewe woleienskappe was 0.49 vir wolkwaliteit (QUAL), 0.28 vir eweredigheid van karteling (ROC), 0.33 vir wolkleur (COL), 0.23 vir wololie (OIL), 0.21 vir stapelformasie (STAPL), 0.22 pens en punte (BANDP), 0.50 vir wolgesigpunt (WFS), 0.15 vir gesigbedekking (FCS), en 0.45 vir pigmentasie (PIGM). Maternale genetiese effekte was betekensivol vir QUAL, ROC en COL, en was 0.06, 0.03 en 0.07 onderskeidelik. Die korrelasie tussen direkte en matrenale genetiese effekte vir QUAL, ROC and COL was -0.62, -0.70 en -0.45 onderskeidelik. Die h²a beraming vir subjektiewe bouvorm-eienskappe was 0.13 vir toplyn (TOPL), 0.39 vir totale plooitelling (TOT), 0.15 vir voorkwart (FQ), 0.16 kote (PS), 0.32 vir hakke (HOCKS) en 0.37 vir die algemene punt vir kop (GEN). Tussen die subjektief beoordeelde bouvormeienskappe was die maternale genetiese effekte slegs betekenisvol vir PS (0.05) terwyl GEN deur c²pe (5%) beïnvloed is. Die korrelasie tussen direkte additiewe en direkte matrenale effekte vir PS was -0.71. Die verbetering van subjektiewe wol- en bouvorm eienskappe deur seleksie lyk waarskynlik op grond van die resultate van die huidige studie. Genetiese korrelasiee (rg) tussen objektiewe eienskappe stem met literatuurwaardes ooreen. Tussen die subjektiewe eienskappe was daar gunstige genetiese korrelasies (rg) tussen ROC en COL (0.31), QUAL met ROC (0.49), QUAL met COL (0.26) en tussen STAPL en BANDP (0.58). Die rg tussen ROC en STAPL (-0.49), QUAL en STAPL (-0.45) en QUAL en BANDP (-0.20) was ongunstig. Ramings van rg tussend subjektiewe bouvormeienskappe was in die algemeen laag, wisselend en nie betekenisvol nie. Die enigste uitsonderings was rg’s tussen HOCKS en FQ (0.71), GEN en TOPL (-0.31) en GEN en TOT (-0.47). Fenotipiese- en omgewingskorrelasies tussen objektiewe en subjektiewe wol- en bouvorm eienskappe was laag tot matig. Maternale korrelasie van onderskeidelik 0.86 en 0.19 is tussen GFW en CFW en tussen CFW en FD gevind. Die rg van LW met subjektiewe woleienskappe was nie betekenisvol nie, met die uitsondering van ‘n matige en gunstige rg van LW met ROC (0.20) en LW met WFS (0.20) wat daarop dui dat swaarder skape waarskynlik meer eweredige wol en hoër punte vir WFS sal hê. Die rg was gunstig met COL (-0.19), STAPL (0.35) en BANDP (0.42). CFW en CY was gunstig verwant met COL, STAPL, BANDP en QUAL wat daarop dui dat skape met hoër vaggewigte en skoonopbrengs wol gehad met ‘n beter kwaliteit en beter punte vir COL, STAPL sowel as vir BANDP gehad het. SL was gunstig verwant aan COL, BANDP en WFS, en negatief verwant aan OIL. Hierdie resultate is ‘n aanduiding dat skape met langer stapels beter punte vir COL, BANDP en WFS sowel as laer tellings vir OIL behoort te hê. Onder die subjektiewe woleienskappe was slegs ROC betekenisvol verwant aan SS (0.33). Matige en gunstige genetiese korrelasies van FD met QUAL, ROC en FCS is beraam, wat daarop dui dat skape met goeie kwaliteit wol ‘n gelykmatige vag en sagter wol op die gesig, sowel and ‘n laer FD behoort te hê. Die ooreenstemmende verhouding van FD met STAPL en BAND was ongunstig. Genetiese korrelasies van CVFD en SDFD met QUAL en ROC was gunstig, maar die eienskappe was ongunstig verwant aan STAPL. Fenotipiese en omgewingskorrelasies tussen objektiewe eienskappe en subjektiewe eienskappe was laag tot hoog en veranderlik in rigting. Op die genetiese vlak was LW gunstig verwant tot al die subjektief beoordeelde bouvormeienskappe wat bestudeer is. Swaarder skape was oor die algemeen minder geplooid, en het beter tellings vir GEN, HOCKS, en FQ sowel as vir TOPL gehad. Beramings van rg was gunstig vir CY met GEN (0.25), HOCKS (0.19), TOT (-0.26) en FQ (0.18), vir FD met PS (-0.16) en TOPL (-0.18), vir CVFD met HOCKS (-0.17), FQ (-0.33) en TOPL (-0.25), tussen CFW en GEN (0.23), en tussen SS en FQ (0.39). Die korrelasies van SDFD met FQ en TOPL was gunstig. Ongunstige korrelasies is beraam tussen SS en TOT (0.25), FD en HOCKS, FD en TOT, tussen vaggewig en TOT sowel as TOPL asook tussen CY en TOT. Fenotipiese- en omgewingskorrelasies tussen objektiewe en subjektiewe woleienskappe was laag tot hoog en veranderlik in rigting. Die resultate dui daarop dat die seleksie vir LW en objektiewe woleienskappe nie die subjektiewe wol- en bouvormeienskappe sal benadeel nie. Die uitsondering is FD, CVFD en SDFD, waar ongunstige genetiese korrelsies met STAPL en BANDP gevind is. Verder, uit hierdie resultate is dit duidelik dat die diskriminsie teen plooie in Merinoskape ekonomies belangrike objektiewe woleienskappe soos SS, FD en vaggewig negatief kan beïinvloed. Seleksie teen plooie moet versigtig gemoniteer word om die risiko van diere met laer vaggewigte en met sterker vesels te verminder. Dit word aanbeveel dat diere met uitermate plooie uit die teeltrop verwyder word.
Afrikaans: Genetiese evaluasie-stelsels het die akkurate beraming van genetiese parameters nodig. Genetiese, fenotipiese en omgewingsparameters vir objektiewe wol, subjektiewe wol, subjektiewe bouvorm, sowel as vir 16-maande gewig is vir Suid-Afrikaanse Merinoskape beraam. Rekords van die Tygerhoek Merino navorsingskudde, insluitende waarnemings op 4 495 diere, die nageslag van 449 vaars en 1 831 moers en gebore in die periode 1989 tot 2004, is gebruik om hierdie parameters te beraam. Die rekords wat gebruik is, is tussen 1969 en 2004 versamel. Vier lyne is in die data verteenwoordig, naamlik: ‘n lyn geselekteer op skoonvaggewig, ‘n lyn geselekteer teen grootmaakverliese, ‘n fynwollyn, sowel as ‘n ongeselekteerde kontrolelyn. Enkel-eienskap gemengede modelle is gebruik. Vaste effekte sluit die effek van geboortestatus (enkel/meerling), geslag (manlik/vroulik), ouderdom van ooi (2-6 jaar), jaar van geboorte (1989-2004), seleksielyn (1-4), en die geslag*geboortejaar interaksie in. Voorlopige ontledings het aangedui dat al die vaste invloede ‘n betekenisvolle (P<0.05) effek op al die kenmerke wat bestudeer is, gehad het. Die toevallige effekte het kombinasies van direkte additiewe, maternale additiewe en maternale permanente omgewingsinvloede sowel as die korrelasie tussen direkte en matrenale additiewe invloede ingesluit. Die direkte oorerflikheid beramings (h²a) vir objektiewe eienskappe was 0.38 vir 16- maande gewig (LW), 0.36 vir rouwol gewig (GFW), 0.40 vir skoonwolgewig (CFW), 0.65 vir skoonopbrengs (CY), 0.37 stapellengte (SL), 0.20 vir stapelsterkte (SS), 0.68 vir veseldeursnit (FD), 0.61 vir die koeffisient van variasie van veseldeursnit (CVFD) en 0.61 vir standaardafwyking van veseldeursnit (SDFD). Die maternale oorerflikheidsberamings was 0.05 vir LW, 0.09 vir GFW, 0.10 vir CFW en 0.05 vir FD. Die proporsie van die totale fenotipiese variansie as gevolg van die maternale permanente omgewing (c²pe) het 5% tot die vaggewigte bygedra. Die korrelasie tuseen die direkte en maternale genetiese effekte vir LW, GFW en CFW was -0.28, -0.65 en -0.70 onderskeidelik. Hierdie resultate wys dat ‘n response op seleksie vir objektief gemete eienskappe hoogs waarskynlik is. Skattings vir h²a vir subjektiewe woleienskappe was 0.49 vir wolkwaliteit (QUAL), 0.28 vir eweredigheid van karteling (ROC), 0.33 vir wolkleur (COL), 0.23 vir wololie (OIL), 0.21 vir stapelformasie (STAPL), 0.22 pens en punte (BANDP), 0.50 vir wolgesigpunt (WFS), 0.15 vir gesigbedekking (FCS), en 0.45 vir pigmentasie (PIGM). Maternale genetiese effekte was betekensivol vir QUAL, ROC en COL, en was 0.06, 0.03 en 0.07 onderskeidelik. Die korrelasie tussen direkte en matrenale genetiese effekte vir QUAL, ROC and COL was -0.62, -0.70 en -0.45 onderskeidelik. Die h²a beraming vir subjektiewe bouvorm-eienskappe was 0.13 vir toplyn (TOPL), 0.39 vir totale plooitelling (TOT), 0.15 vir voorkwart (FQ), 0.16 kote (PS), 0.32 vir hakke (HOCKS) en 0.37 vir die algemene punt vir kop (GEN). Tussen die subjektief beoordeelde bouvormeienskappe was die maternale genetiese effekte slegs betekenisvol vir PS (0.05) terwyl GEN deur c²pe (5%) beïnvloed is. Die korrelasie tussen direkte additiewe en direkte matrenale effekte vir PS was -0.71. Die verbetering van subjektiewe wol- en bouvorm eienskappe deur seleksie lyk waarskynlik op grond van die resultate van die huidige studie. Genetiese korrelasiee (rg) tussen objektiewe eienskappe stem met literatuurwaardes ooreen. Tussen die subjektiewe eienskappe was daar gunstige genetiese korrelasies (rg) tussen ROC en COL (0.31), QUAL met ROC (0.49), QUAL met COL (0.26) en tussen STAPL en BANDP (0.58). Die rg tussen ROC en STAPL (-0.49), QUAL en STAPL (-0.45) en QUAL en BANDP (-0.20) was ongunstig. Ramings van rg tussend subjektiewe bouvormeienskappe was in die algemeen laag, wisselend en nie betekenisvol nie. Die enigste uitsonderings was rg’s tussen HOCKS en FQ (0.71), GEN en TOPL (-0.31) en GEN en TOT (-0.47). Fenotipiese- en omgewingskorrelasies tussen objektiewe en subjektiewe wol- en bouvorm eienskappe was laag tot matig. Maternale korrelasie van onderskeidelik 0.86 en 0.19 is tussen GFW en CFW en tussen CFW en FD gevind. Die rg van LW met subjektiewe woleienskappe was nie betekenisvol nie, met die uitsondering van ‘n matige en gunstige rg van LW met ROC (0.20) en LW met WFS (0.20) wat daarop dui dat swaarder skape waarskynlik meer eweredige wol en hoër punte vir WFS sal hê. Die rg was gunstig met COL (-0.19), STAPL (0.35) en BANDP (0.42). CFW en CY was gunstig verwant met COL, STAPL, BANDP en QUAL wat daarop dui dat skape met hoër vaggewigte en skoonopbrengs wol gehad met ‘n beter kwaliteit en beter punte vir COL, STAPL sowel as vir BANDP gehad het. SL was gunstig verwant aan COL, BANDP en WFS, en negatief verwant aan OIL. Hierdie resultate is ‘n aanduiding dat skape met langer stapels beter punte vir COL, BANDP en WFS sowel as laer tellings vir OIL behoort te hê. Onder die subjektiewe woleienskappe was slegs ROC betekenisvol verwant aan SS (0.33). Matige en gunstige genetiese korrelasies van FD met QUAL, ROC en FCS is beraam, wat daarop dui dat skape met goeie kwaliteit wol ‘n gelykmatige vag en sagter wol op die gesig, sowel and ‘n laer FD behoort te hê. Die ooreenstemmende verhouding van FD met STAPL en BAND was ongunstig. Genetiese korrelasies van CVFD en SDFD met QUAL en ROC was gunstig, maar die eienskappe was ongunstig verwant aan STAPL. Fenotipiese en omgewingskorrelasies tussen objektiewe eienskappe en subjektiewe eienskappe was laag tot hoog en veranderlik in rigting. Op die genetiese vlak was LW gunstig verwant tot al die subjektief beoordeelde bouvormeienskappe wat bestudeer is. Swaarder skape was oor die algemeen minder geplooid, en het beter tellings vir GEN, HOCKS, en FQ sowel as vir TOPL gehad. Beramings van rg was gunstig vir CY met GEN (0.25), HOCKS (0.19), TOT (-0.26) en FQ (0.18), vir FD met PS (-0.16) en TOPL (-0.18), vir CVFD met HOCKS (-0.17), FQ (-0.33) en TOPL (-0.25), tussen CFW en GEN (0.23), en tussen SS en FQ (0.39). Die korrelasies van SDFD met FQ en TOPL was gunstig. Ongunstige korrelasies is beraam tussen SS en TOT (0.25), FD en HOCKS, FD en TOT, tussen vaggewig en TOT sowel as TOPL asook tussen CY en TOT. Fenotipiese- en omgewingskorrelasies tussen objektiewe en subjektiewe woleienskappe was laag tot hoog en veranderlik in rigting. Die resultate dui daarop dat die seleksie vir LW en objektiewe woleienskappe nie die subjektiewe wol- en bouvormeienskappe sal benadeel nie. Die uitsondering is FD, CVFD en SDFD, waar ongunstige genetiese korrelsies met STAPL en BANDP gevind is. Verder, uit hierdie resultate is dit duidelik dat die diskriminsie teen plooie in Merinoskape ekonomies belangrike objektiewe woleienskappe soos SS, FD en vaggewig negatief kan beïinvloed. Seleksie teen plooie moet versigtig gemoniteer word om die risiko van diere met laer vaggewigte en met sterker vesels te verminder. Dit word aanbeveel dat diere met uitermate plooie uit die teeltrop verwyder word.
Description
Keywords
Dissertation (M.Sc.Agric. (Animal, Wildlife and Grassland Sciences))--University of the Free State, 2007, Merino sheep -- Breeding -- South Africa -- Western Cape, Merino sheep -- South Africa -- Western Cape -- Genetics, Wool, Subjective wool and conformation traits, Genetic parameters, Phenotypic and environmental parameters, Objective wool traits, Live weight