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Genetic improvement of beef cattle in a tropical environment with special reference to the Gudali and Wakwa breeds in Cameroon

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dc.contributor Erasmus, G. J.
dc.contributor Tawah, C. L.
dc.creator Ebangi, Achenduh Lot
dc.date 2018-04-10T08:48:48Z
dc.date 2018-04-10T08:48:48Z
dc.date 1999-11
dc.date.accessioned 2018-06-24T05:29:50Z
dc.date.available 2018-06-24T05:29:50Z
dc.identifier http://hdl.handle.net/11660/8171
dc.identifier.uri http://hdl.handle.net/11660/8171
dc.description English:In an attempt to genetically Improve Gudali beef cattle JO Cameroon, two selection experiments were conducted between 1968 and 1988 at the Animal Production and Research Stations of Wakwa, Ngaoundere. The one experiment involved a two-breed synthetic beef breed, the Wakwa, obtained from inter se matings of the first filial generation of American Brahman (50%) x Gudali (50%) crosses. The other experiment involved recurrent selection of the indigenous purebred Gudali in an effort to enhance its beef production without any serious detrimental effects to its adaptational qualities.In order to assess the genetic progress of the two experiments, a study using mixed model methodology was carried out. The objectives were to quantify factors affecting growth traits, estimate (eo )variance components, predict genetic merit (breeding values) for direct and maternal performance and determine genetic progress by examining direct and maternal genetic trends for all animals. A total of 2886 records for birth weight (BWT), 2732 for average preweaning daily gain (ADG), 2899 for weaning weight (WWT), 2098 for yearling weight (YWT) and 1957 for eighteen months weight (EWT) of Gudali cattle were used in the study. Corresponding number of records for the Wakwa were 1793, 1656,1838, 1372and 1328. The results indicated that sire, sex, season (S), calf birth year (C), herd (H), HxSxC interaction, cowage group and ages at weaning (WAGE), yearling (YAGE) and eighteen months (EAGE), as well as covariates for weaning, yearling and eighteen month weights, were significant (p<0.05) sources of variation for these traits. Therefore, for reliablegenetic parameter estimations and evaluation of genetic merit of individual candidate animals for selection, these sources of variation should be taken into consideration. Hence the inclusion of these factors in the mixed model for the estimation of genetic parameters and prediction of breeding values.Estimates obtained for direct, maternal and total heritabilities were 0.37, 0.05 and 0.21 for BWT; 0.24, 0.17 and 0.07 for ADG; 0.27,0.19 and 0.11 for WWT; 0.51, 0.20 and 0.22 for YWT; and 0.18, 0.02 and 0.18 for EWT, respectively, in the Gudali. Corresponding estimates in the Wakwa were 0.55, 0.23 and 0.18 for BWT; 0.26, 0.07 and 0.12 for ADG; 0.28, 0.09 and 0.15 for WWT; 0.18, 0.00 and 0.17 for YWT and 0.14, 0.06 and 0.17 for EWT. Estimates for genetic correlations between direct and maternal effects were generally highly negative and ranged from -0.76 for ADG to -0.98 for YWT in the Wakwa and from -0.77 for WWT to - 0.88 for BWT in the Gudali. However, in both breeds the genetic correlation was nil for EWT. These estimates obtained are indicative that there are distinct possibilities of improving direct preweaning and/or postweaning growth in the both breeds through selection. However, a high selection intensity for direct performance may in the long run be detrimental to maternal performance as a result of the generally strong genetic antagonism between them. Although some estimates of genetic parameters for preweaning weight from one to seven months traits were not obtained for the Wakwa breed due to limited data, estimates obtained for the Gudali indicated that the highest, although moderate, estimate for maternal heritability (0.24) was for weight at two months of age. Therefore, an attempt to optimise direct and maternal performance in the Gudali through selection could be mosteffective at two months and at yearling, respectively. It is suggested that the apparent genetic antagonism generally found between direct and maternal ability be specifically investigated using more suitable data.An assessment of genetic progress indicated positive and significant (p<O.Ol) mean annual direct trends of 0.02 and 0.03 kg/year for BWT; 0.0005 and 0.0005 kg/year for ADG; 0.23 and 0.20 kg/year for WWT; 0.33 and 0.24 kg/year for YWT and 0.25 and 0.24 kg/year for EWT in the Gudali and the Wakwa, respectively. The difference between direct responses for all traits in both breeds were not significant. Corresponding trends for maternally influenced traits were -0.01 and -0.02; -0.1 and -0.3; -0.10 and -0.06; -0.15 and -0.00, -0.01 and 0.04. With the exception of ADG in the Gudali and EWT in the Wakwa, maternal trends were also significant (p<0.05) but negative. Considering the fact that the Wakwa breed has been shown to be more susceptible to streptothricosis and less tolerant to the tropical environment than the Gudali, it is economically justified to improve the purebred Gudali by selection rather than crossbreeding to the American Brahman or other exotic breeds.
dc.description Afrikaans:In 'n· poging om Gudali vleisbeeste in Kameroen geneties te verbeter, is twee seleksieproewe tussen 1968 en 1988 by die Wakwa dierproduksie- en navorsingstasie te Ngaoudere uitgevoer. Die een proef het 'n sintetiese ras behels wat ontstaan het uit 'n terminale kruis tussen die Amerikaanse Brahman (50%) en die Gudali 50%. Die ander proef het herhalende seleksie van die inheemse suiwer Gudali behels in 'n poging om sy vleisproduksie te verhoog sonder benadeling van aanpasbaarheid. Om genetiese vordering in die twee proewe vas te stel, is 'n studie, waar van gemengde model prosedures gebruik gemaak is, onderneem. Die doel was om die faktore wat groeieienskappe beïnvloed te kwantifiseer, (ko) variansiekomponente en gevolglike direkte en maternale genetiese tendense te beraam sowel as om die genetiese meriete (teeltwaardes) van al die diere vir direkte sowel as maternale prestasie te voorspel. 'n Totaal van 2886 rekords vir geboortegewig (BWT), 2732 vir gemiddelde daaglikse toename voor speen (ADG), 2899 vir speengewig (WWT), 2098 vir jaaroudgewig (YWT) en 1957 vir gewig op 18 maande (EWT) is gebruik vir die studie met die Gudali-ras. Ooreenstemmende aantal rekords vir die Wakwa was onderskeidelik 1993,1656,1838,1372 en 1328.Die resultate verkry het aangedui dat vaar, geslag, seisoen (S), kalf geboortejaar (C), kudde (H), HxSxC interaksie, koei-ouderdomsgroep en werklike ouderdom met speen (WAGE), jaaroud (YAGE) en agtien maande (EAGE) sowel as die kovariate vir speen, jaaroud en agtien maande betekenisvolle (p<0.05) bronne van variasie was. Vir betroubare beraming van genetiese parameters en teeltwaardes van individuele diere, sal hierdie bronne van variasie derhalwe in ag geneem moet word wat die geval was in hierdie studie. Beramings verkry vir direkte-, maternale- en totale oorerflikheid was onderskeidelik 0.37, 0.05 en 0.21 vir BWT; 0.24, 0.17 en 0.07 vir ADG; 0.27,0.19 en 0.11 vir WWT; 0.51, 0.20 en 0.22 vir YWT en 0.18, 0.02 en 0.18 vir EWT in die Gudali. Ooreenstemmende beramings vir die Wakwa was onderskeidelik 0.55, 0.23 en 0.18 vir BWT; 0.26, 0.07 en 0.12 vir ADG; 0.28, 0.09 en 0.15 vir WWT; 0.18, 0.00 en 0.17 vir YWT en 0.14, 0.06 en 0.17 vir EWT. eramings van genetiese korrelasies tussen direkte genetiese en maternale effekte was deurgaans hoogs negatief en het gewissel van -0.76 vir ADG en -0.98 vir YWT, albei verkry in die Wakwa ras. Die beramings verkry dui daarop dat genetiese verbetering van direkte voorspeense en/of naspeense groei deur seleksie 'n besliste moontlikheid in albei rasse is. 'n Hoë seleksieintensiteit vir direkte prestasie mag egter op die lange duur skadelik wees vir maternale prestasie as gevolg van die verkreë hoë genetiese antagonisme tussen die twee. Alhoewel beramings van sommige genetiese parameters vir voorspeense gewigte tussen een en sewe maande nie vir die Wakwa verkry is nie weens beperkte data, het beramings verkry vir die Gudali getoon dat die hoogste, hoewel slegs matig, beraming vir maternale oorerflikheid (0.24) vir gewig op twee maande ouderdom was. Seleksie vir gewig op twee maande ouderdom in die Gudali en op jaaroud in die Wakwa blyk derhalwe die mees effektief te mag wees om direk en maternale prestasie te optimaliseer. Dit word ernstig voorgestel dat die skynbare genetiese antagonisme wat redelik algemeen verkry word tussen direkte en maternale vermoë spesifiek ondersoek word deur gebruik te maak van meer gepaste data. 'n Beraming van genetiese vordering het betekenisvol (p<0.05) positiewe jaarlikse gemiddelde tendense getoon van 0.02 en 0.03 kg per jaar vir BWT, 0.0005 en 0.0005 kg/jaar vir ADG, 0.23 en 0.20 kg/jaar vir WWT, 0.33 en 0.24 kg/jaar vir XWT en 0.25 en 0.24 kg/jaar vir EWT vir onderskeidelik Gudali en Wakwa. Die verskil in tendense verkry vir die Gudali en Wakwa was nie-betekenisvol vir al die eienskappe. Ooreenstemmende tendense verkry vir die eienskappe soos maternaal beïnvloed was -0.01 en -0.02; -0.1 en - 0.3; -0.10 en -0.06; -0.15 en -0.00; -0.01 en -0.04. Met die uitsondering van ADG in die Gudali en EWT in die Wakwa, was maternale tendense ook betekenisvol (p<0.05) maar negatief. Siende dat dit reeds aangetoon is dat die Wakwa ras meer vatbaar vir streptothricosis en minder tolerant vir tropiese toestande as die Gudali is, kan dit ekonomies meer regverdig wees om die suiwer Gudali deur seleksie te probeer verbeter as om gebruik te maak van . die haltkruis Wakwa.
dc.language en
dc.publisher University of the Free State
dc.rights University of the Free State
dc.subject Beef cattle -- Breeding -- Cameroon
dc.subject Beef cattle -- Genetics -- Cameroon
dc.subject Thesis (Ph.D. (Animal Science))--University of the Free State, 1999
dc.title Genetic improvement of beef cattle in a tropical environment with special reference to the Gudali and Wakwa breeds in Cameroon
dc.type Thesis


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