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The first part of the study compared a commercial, the Dorper as an arguably adapted commercial breed to the Namaqua Afrikaner as an unselected, indigenous, far-tail breed. The Dorper conclusively outperformed the Namaqua Afrikaner with reference to live weight and growth traits. On the other hand, Namaqua Afrikaner lambs were superior to Dorpers for an adaptive trait like total tick count. Lamb survival was unaffected by breed. When meat traits were considered, it was evident that Dorper lambs outperformed their Namaqua Afrikaner contemporaries for important attributes associated with size and meat yield, namely carcass weight and dressing percentage. Dorper carcasses also attained better grades and were more tender according to instrumental measurements (Warner Brazler equipment). Dorper lambs were fatter than Namaqua Afrikaner lambs, as derived from the backfat thickness at the 13th rib and the rump. While leaner meat would be preferred by health-conscious consumers, it is important to note that, under the conditions of the study, Dorper carcasses were more likely to be in the preferred grades. In the second part of the study, Dorpers were evaluated against the SA Mutton Merino (SAMM; the most numerous dual-purpose breed in South Africa), as well as the reciprocal cross between the two breeds. No conclusive breed differences were found for weight traits, lamb survival, tick counts or meat traits. However, there was a suggestion that lamb survival of Dorpers was higher than that of their SAMM contemporaries (P = 0.08), but significance could not be demonstrated. Crossbred progeny outperformed the midparent value by 6.3% for weaning weight. The corresponding study on meat traits was constrained by low numbers. However, it was evident that the observed heterosis for weaning weight was also present a later growth stage. Direct heterosis estimates amounted to 7.7% for slaughter weight and 7.1% for carcass weight. These estimates were consistent with the literature for, Lesotho National Manpower Development secretariat (NMDS)

The study investigated genetic parameters and immunological responses to tick infestation in three South African sheep breeds (Namaqua Afrikaner [NA], Dorper and SA Mutton Merino [SAMM]). The study aimed to estimate genetic and crossbreeding parameters for tick count (TC) and weaning weight (WW), to examine the histology of tick attachment and control sites, to select reference genes for normalizing gene expression data in this study, to compare cytokines gene expression at tick attachment and control sites and finally to compare cutaneous hypersensitivity reactions to unfed larvae extracts (ULE) of Rhipicephalus evertsi evertsi between NA, Dorper and SAMM sheep. Genetic parameters for WW and TC were estimated using data of lambs maintained on the Nortier Research Farm from 2010 to 2015. Firstly, data of purebred commercial Dorper and SAMM lambs were combined with data of their reciprocal crosses to assess breed effects and the possible effect of non-additive genetic variation on WW and TC. In the second analysis, data of purebred commercial Dorper lambs were combined with data of the unimproved, indigenous NA and the NA x Dorper cross. In Analysis 1 the coefficient of variations (CV) were 24%, 95% and 50% for WW, untransformed total TC and square root transformed total TC, respectively. Genotype affected WW but not TC. A heterosis estimate of approximately 4% was derived for WW. A single-trait h² estimate for TC was 0.11±0.09. A model analysing across-genotype h² yielded a slightly lower h² estimate of 0.08 ± 0.07. In Analysis 2 the CV were 27% and 55% for WW and square root transformed total TC, respectively. WW and TC were affected by genotype. WW exhibited heterosis amounting to 8.5% while the corresponding value for TC amounted to -23%. The single-trait h² estimate for TC was 0.06±0.05. A model analysing across-genotype h² yielded a substantially higher h² estimate of 0.27±0.07. These results suggest that genetic variation in TC was primarily associated with di

English: Pedigree and performance data of a well-documented ostrich breeding resource flock was used to (1) investigate the flock structure, (2) estimate variance and (co)variance components for egg and day-old chick weight (individual traits), (3) estimate genetic and environmental parameters for egg and chick production, mean egg and day-old chick weights and hatchability within breeding seasons (hen traits) and (4) investigate early identification of superior animals using random regression models for repeated measures (longitudinal) data over years. The average level of pedigree completeness of 40 074 birds of a pair-breeding ostrich flock maintained from 1978 to 2005 at the Oudtshoorn Research Farm, South Africa was high (99.3%) in the first generation and the average level of inbreeding (F) was low at 0.51%. The estimated measures of variability were: effective genome equivalents = 47.3, effective number of founders = 59 and the effective number of ancestors = 58. The numbers of ancestors responsible for 100%, 50% and 20% of the variation in the reference population (birds with both parents known), were equal to 254, 21 and 6 respectively. The generation interval in years calculated as the average age of parents when their offspring which were kept for reproduction were born, amounted to 7.72 ± 4.79 years. The linear regressions of rate of inbreeding on year of hatch for the two distinct periods, 1995-2002 and 2003-2005, were 0.08% and -0.07% per year respectively. The estimate of effective population size (Ne) computed via the increase in the individual rate of inbreeding was 112.7 animals. The results of this study indicated that the population under study was at an acceptable level of genetic variability. Pedigree and performance data for 71 147 individual egg records collected between 1991 to 2005 were used to estimate genetic parameters for egg weight (EWT), live day-old chick weight (CWT) and hatchability (H). Heritability estimates (±SE) were 0.12 ± 0.0, Afrikaans: Stamboom-en prestasie-data van 'n goed gedokumenteerde volstruis telinghulpbron-kudde is gebruik om (1) ondersoek intestel na die kuddestruktuur, (2) beraamde variansie en (ko)variansie komponente vir eier- en dag-oud kuiken-gewigte (eienskappe van die individu), (3) genetiese- en omgewingparameters te beraam vir eierproduksie, kuikenproduksie sowel as vir gemiddelde eier- en dag-oudkuikengewig en uitbroeibaarheid binne teelseisoene (wyfie-eienskappe) en (4) die vroeë identifisering van diere met hoë genetiese meriete deur die gebruik/ ondersoek van toevalsregressiemodelle vir herhaalde metings van rekords oor jare. Die gemiddelde vlak van die stamboomvolledigheid van 40 074 eiers van 'n afgepaarde volstruisbroeitrop, vanaf 1978 tot 2005 op die Oudtshoorn Navorsingsplaas, Suid-Afrika was hoog (99.3%) in die eerste generasie en die gemiddelde vlak van inteling (F) was laag op 0.51%. Die beraamde maatstawwe van variasie was: effektiewe genoom ekwivalente = 47.3, effektiewe aantal stigters = 59 en die effektiewe aantal voorvaders = 58. Die getalle voorvaders verantwoordelik vir 100%, 50% en 20% van die variasie in die verwysingspopulasie (voëls met beide ouers bekend), was onderskeidelik 254, 21 en 6. Die generasie-interval, aangedui in jare, bereken as die gemiddelde ouderdom van die ouers wanneer hulle nageslag wat vir reproduksie doeleindes geselekteer is, gebore word, het 7.70 ± 4.87 jaar beloop. Die lineêre regressies van die tempo van inteling op jaar van uitbroei vir die twee afsonderlike periodes, 1995 - 2002 en 2003-2005, was onderskeidelik 0.08% en - 0.07% per jaar. Die beraming van die effektiewe bevolkingsgrootte (Ne) bereken deur middel van die toename in die individuele koers van inteling was 112.7 diere. Die resultate van hierdie studie het aangedui dat die populasie tans aanvaarbare vlakke van genetiese variansie handaaf. Stamboom- en prestasie-data van 71 147 individuele eierrekords tussen 1991 tot 2005 ingesamel, is gebruik om genetiese par

English: The length of productive life is of major economic importance in dairy cattle production. Simple breeding objectives such as selection for increased production in dairy cattle have led to a significant decline in fitness traits. A multi-purpose breeding objective that includes other traits such as length of productive life should be considered. Herd life reflects the ability of a cow to avoid being culled for low production, low fertility, or illness. Herd life can be used in breeding programs if genetic parameters are known. The objectives of the study were to: (1) estimate genetic parameters for functional herd life for the South African Jersey breed using a multiple trait linear model, (2) develop a prototype breeding value for functional herd life for the South African Jersey breed, (3) estimate genetic relationships between functional herd life and conformation traits in the South African Jersey breed and (4) assess inbreeding depression for functional herd life in the South African Jersey breed based on level and rate of inbreeding. A measure of herd life called functional herd life was considered in the current study. Functional herd life refers to herd life adjusted for milk production in the first lactation. In this study functional herd life was defined as survival in each of the first three lactations. Functional herd life was denoted by a 1 if a cow survived and 0 otherwise. Analyses to estimate genetic parameters for functional herd life were carried out as follows. Data and pedigree records on purebred Jersey cows that participated in National Milk Recording and Improvement Scheme were analyzed. Data before editing comprised test-day and lactation yields on milk, fat and protein yields from 252 629 Jersey cows born between 1968 and 2005. After editing, 181 269 cow records from 636 herds recorded over 16 years were available for analysis. Estimates of genetic parameters for herd life were obtained using REML procedures fitting a multiple-trait, Afrikaans: Die produktiewe leeftyd van melkkoeie is van groot ekonomiese belang in melkbeesproduksiestelsels. Eenvoudige teeltdoelwitte, soos seleksie vir verhoogde produksie in melkbeeste, het tot ‘n betekenisvolle afname in fiksheidseienskappe gelei. ‘n Veeldoelige teeltdoelwit, wat ander eienskappe soos die lengte van produktiewe lewe insluit, behoort oorweeg te word. Kuddeleeftyd weerspieël die vermoë van koeie om nie weens lae melkproduksie, lae vrugbaarheid of siekte uitgeskot te word nie. Kuddeleeftyd kan, indien die genetiese parameters bekend is, in teeltprogramme gebruik word. Die doelwitte van die studie was om: (1) genetiese parameters vir funksionele kuddeleeftyd vir Suid-Afrikaanse Jerseys te beraam, deur van ‘n meervoudige-eienskap-liniêre model gebruik te maak, (2) ‘n prototipe teeltwaarde vir funksionele kuddeleeftyd vir Suid-Afrikaanse Jerseys te ontwikkel, (3) die genetiese verwantskappe tussen funksionele kuddeleeftyd en bouvormeienskappe vir Suid- Afrikaanse Jerseys te bepaal en (4) die afname in funksionele kuddeleeftyd in die Suid- Afrikaanse Jerseys populasie is gebaseer op die vlak- en tempo van inteling. In die huidige studie is kuddeleeftyd beskryf as funksionele kuddeleeftyd. Funksionele kuddeleeftyd verwys na kuddeleeftyd wat vir eerste laktasiemelkproduksie aangepas is. In hierdie studie is funksionele kuddeleeftyd gedefinieer as oorlewing gedurende elkeen van die eerste drie laktasies. Funksionele kuddeleeftyd is met ‘n 1 aangedui indien ‘n koei die laktasie oorleef het en met ‘n 0 (nul) indien nie. Om die genetiese paramaters vir funksionele kuddeleeftyd te beraam, is die beramings as volg uitgevoer: Die melkproduksie- en stamboomrekords van suiwergeteelde Jerseykoeie wat aan die Nasionale Melkaantekening en Verbeteringskema deelgeneem het, is in die analise gebruik. Voor die redigering van die data, het dit bestaan uit die toetsdag- en laktasierekords vir melk-, vet- en proteïenproduksie van 252 629 Jersey koeie wat tussen 1968 en 20, Agricultural Research Council, National Research Foundation (NRF), South African Jersey Breed Society

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 correla, 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, W.K. KELLOGG Foundation

English: Genetic (co)variances for yearling body weight (BW), clean fleece weight (CFW) and mean fibre diameter (MFD) in the SA Dohne Merino population were estimated using records of 107 389 animals recorded between 1992 and 2004. The data include records of 1 530 sires and 45 178 dams. An animal model with direct and maternal additive, maternal permanent and temporary environmental effects was fitted for all traits. Sire-flock (SF) and sire-flock-year-season (SFYS) was included as additional random effects. Fixed effects were (FYSSM) (1594 classes), type of birth (singles, multiples), age of dam (2 to 7+ years) and average age (± SD) at measurement fitted as a linear covariate (385 ± 12 days). Estimates obtained by single -trait analyses were used as starting values in three-trait analyses. The direct genetic heritability estimates for FD, CFW and BW obtained from the three-trait analysis were 0.447 (0.009), 0.216 (0.008) and 0.277 (0.008) respectively. The genetic correlations were 0.050 between BW and CFW, 0.100 between BW and FD and 0.139 between FD and CFW. The phenotypic correlations were 0.318 between BW and CFW, 0.129 between BW and FD and 0.180 between FD and CFW. Direct genetic correlations of BW, CFW and MFD were positive, which suggest that selection for bigger and heavier sheep would generally lead to a stronger MFD and higher CFW. Because these values are very low the subsequent effect of this phenomenon would be that the effect of selection for body traits on fleece traits would be very small and vice versa. Genetic trends were calculated using the annual average breeding value estimates (EBV) for each trait. According to the genetic trends derived, the selection policy followed did cause genetic change in the traits studied, even though it was slow. The level of inbreeding (F) in the South African Dohne Merino sheep population is very low. The proportion of animals that was inbred to some extent increased from 0% (average F=0) in 1980 to 38% in 2003, Afrikaans: ‘n Analise van die Dohne Merino skaapras in Suid Afrika is gedoen. Die data dateer vanaf 1992 tot 2004. Genetiese parameters van onderskeidelik groei- en woleienskappe vir 12 tot 14 maande oue diere is beraam. Veseldikte (VD), skoon vaggewig (SVM) en liggaamsgewig (LM) inligting van 107 389 diere wat 1 530 vaars en 45 178 moers insluit, was beskikbaar vir ontledings. Benewens direkte genetiese-, maternale genetiese- en omgewingseffekte, is vaar-kudde en vaar-kudde - jaar-seisoen effekte as addisionele toevallige effekte ingesluit. Die waardes wat bereken is uit enkel-eienskap analises is gebruik as beginwaardes vir die drie - eienskap analises. Die beraamde direkte oorerflikhede van die drie-eienskap analises was 0.447 (0.009) vir VD, 0.216 (0.008) vir SVM en 0.277 (0.008) vir LM. Die genetiese korrelasies tussen LM en SVM was 0.050, 0.100 tussen LM en VD en 0.139 tussen VD en SVM. Die fenotipiese korrelasies tussen LM en SVM was 0.318, 0.129 tussen LM en VD en 0.180 VD en SVM. Genetiese korrelasies tussen LM, SVM en VD was positief, wat ‘n aanduiding is dat seleksie vir ‘n groter dier kan lei tot sterker wol en ‘n swaarder vag. Omdat hierdie waardes baie laag is, sal die gevolglike gekorreleerde effek van seleksie vir groei-eienskappe op woleienskappe baie laag wees en vice versa. Genetiese tendense is verkry deur die gemiddelde voorspelde teelwaarde (VTW) per jaar vir elke eienskap te bereken. Uit die genetiese tendense is dit duidelik dat seleksie gebaseer op teeltdoelwitte, daargestel deur die Genootskap, wel genetiese vordering in al drie eienskappe getoon het , alhoewel vordering baie stadig was. Die vlak van inteling in die Suid Afrikaanse Dohne Merino populasie is tans laag. Produksie en reproduksie vlakke sal dus nie negatief deur inteling beinvloed word nie. Die persentasie diere wat tot ‘n sekere mate ingeteel is, het gestyg van 0% (gemiddelde F=0%) in 1980 tot 38% (gemiddelde F=1.22%) in 2003. Geen betekenisvolle inteeltverval kon gevind word

English: A line x environment interaction study with grade Afrikaner cattle was established at Matopos Research Station, Zimbabwe, in 1956. From a grade pool of 200 cows, two selection lines of 100 cows were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). Bull selection based on weight at weaning was to develop lines adapted to their respective environments. After approximately 2 generations of selection, lines were sub-divided into 4 sub-lines, consisting of 75 cows each. One sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected within control lines, while replacement heifers were generated within sub-line. Heifers were selected on weight at mating and replacement rates were dictated by the sub-line with the least number of suitable animals (>265kg). Data collected over a 40-year period representing 6 generations of selection were analyzed to determine a) genetic and environmental factors influencing calf growth and survival and cow fertility, b) direct and correlated responses to selection and c) presence and importance of genotype x environment interactions. Productivity in the S environment, in terms of calf growth and cow fertility, was superior compared with the NS environment. While there were no differences in birth weight, calves born early in the S environment were estimated to be 90kg (33%) heavier at 18 months than calves born late in the NS environment. The performance of calf growth from birth to 18 months in this study has emphasized the importance of matching animal physiological status with seasonal changes in the sub-tropics. Given the significant and consistent detri, Afrikaans: ‘n Lyn x omgewing-interaksiestudie met graad-Afrikanerbeeste is in 1956 by Matopos Navorsingstasie, Zimbabwe, onderneem. Vanuit ‘n poel van 200 koeie is twee seleksielyne van 100 koeie elk in verskillende bestuursomgewings grootgemaak. Die lyn wat geen byvoeding ontvang het nie (NS) was dwarsdeur die jaar op weiding alleen aangewese en is gepaar om met die aanvang van die reënseisoen (Desember tot Februarie) te kalf. Die lyn wat byvoeding ontvang het (S) het proteïenryke aanvullings gedurende die droë seisoen ontvang en is gepaar om voor die aanvang van die reëns (Oktober tot Desember) te kalf. Bulseleksie gebaseer op gewig met speen is gemik op ontwikkeling van lyne wat by hul spesifieke omgewings aangepas sou wees. Na ongeveer twee generasies van seleksie is lyne onderverdeel in 4 sub-lyne wat uit 75 koeie elk bestaan het. Een sub-lyn het in elke omgewing as kontrole gebly. Die oorblywende sublyne is tussen die omgewings verdeel. Bulle is uit die kontrolelyne geselekteer, terwyl vervangingsverse uit die sublyne gekom het. Verse is geselekteer op grond van gewig met paring en vervangings is gedikteer deur die die sub-lyn wat die kleinste getal geskikte diere gehad het (265 kg). Data wat oor ‘n 40-jaar periode verteenwoordigend van 6 geslagte se seleksie versamel is, is ontleed ten einde te bepaal a) watter genetiese en omgewingsfaktore kalfgroei en –oorlewing en koeivrugbaarheid beïnvloed, b) wat die direkte en gekorreleerde responsie op seleksie is en c) die teenwoordigheid en belangrikheid van genotipe- x omgewings-interaksies. Wat betref kalfgroei en koeivrugbaarheid was produktiwiteit in die S-omgewing meerderwaardig teenoor dié in die NS-omgewing. Terwyl daar geen verskille in geboortege wigte was nie, is beraam dat kalwers wat vroeg in die S-omgewing gebore is, 90 kg (33%) swaarder op 18 maande was as dié wat laat in die NS-omgewing gebore is. Die prestasie van kalfgroei vanaf geboorte tot 18 maande in hierdie studie het beklemtoon hoe belangrik di

English: The present study was carried out to estimate genetic, phenotypic and environmental parameters for growth traits, genetic trends as well as the level of inbreeding in the South African Brahman breed. The data used were obtained from the South African Brahman Breeders’ Society and consisted of pedigree information of 181 508 animals and 221 015 performance records, ranging from birth to 18-months weight /final weight collected between 1955 and 2002. Performance records available before editing as classified according to age ranges were birth weight (BWT) = 67 336, weaning weight (WWT) (80–300 days) = 62 159, yearling weight (YWT) (301-500 days) = 41 313 and final weight (FWT) (501-900 days) = 32 602. The linear animal model used included the fixed effects of contemporary group (herd-year-season), sex, management group, age of the calf, age of the dam. Direct genetic, maternal genetic and permanent maternal environmental as random effects as well as sire x herd-year-season interaction as an additional random effect. Preliminary analyses showed that all fixed effects had a significant (P<0.0001) effect on all traits studied. Genetic parameters for growth traits were estimated using ASREML software by fitting univariate and bivariate animal models. Production traits considered after editing were BWT = 41 509, WWT = 37 705, YWT = 22 682 and FWT = 13 055 records collected between 1985 and 2002. The reason for using the data only from 1985 is that only a small number of records were recorded up to 1984. The direct heritability estimates of BWT, WWT, YWT and FWT were 0.28, 0.14, 0.14 and 0.18 respectively. The corresponding maternal heritability estimates were 0.11, 0.06, 0.05 and 0.03 respectively. The maternal permanent environmental component due to the dam contributed 3 - 7 % of the total phenotypic variance of the traits under consideration. The corresponding contribution of sire x herd-year-season interaction ranges from 5 - 6%. The genetic correlation betwee, Afrikaans: Die doel van hierdie studie wa s om genetiese, fenotipiese en omgewingsparameters vir groei - eienskappe vir die Suid - Afrikaanse Brahmanras te beraam, asook genetiese tendense en die vlak van inteling by dié ras. Data met stamboominligting van 181 508 diere en 221 015 prestasie - rekords w at wissel van geboorte - tot 18 - maandegewig / finale gewig, versamel tussen 1955 en 2002, is van die Suid - Afrikaanse Brahmaantelersvereniging verkry. Onverwerkte prestasie data wat beskikbaar is, word geklassifisser volgens die verskillende ouderdoms groepe . Hierdie prestasie data is as volg: geboortegewig (BWT) = 67 336, speengewig (WWT) (80 - 300 dae) = 62 159, jaar - oudgewig (YWT) (301 - 500 dae) = 41 313 e n finale gewig (FWT) = 32 602. Die lineêre dieremodel wat gebruik is het die volgend vaste effekte ingesl uit , kontemporêre groep (kudde - jaar - seisoen), asook geslag, bestuursgroe p, ouderdom van die kalf, ouder dom van die moeder . D irekte genetiese , maternale genetiese en permanent maternale omgewing as toevallige effekte , so wel as vaar x kudde - jaar - seisoen int eraksie as ‘n addisionele toevallige effek . Voorlopige ontledings het getoon dat alle vaste effekte ‘n hoogs betekenisvolle (P< 0.0001) effek op alle eienskappe wat bestudeer is gehad het. Genetiese parameters vir groei - eienskappe is beraam deur gebruik te maak van die ASREML - sagteware deur enkel - en twee - eienskapdieremodelle te pas. Na verwerking was die volgende aantal rekords beskibaar , BWT = 41 509, WWT = 37 705, Y WT = 22 682 en FWT = 13 055. Hierdie rekords is tussen 1985 en 2002 ingesamel is. Die r ede waarom dat slegs vanaf 1985 af gebruik word is, dat daar min record was tot en met 1984. Die direkte oorerflikheidsberamings van BWT, WWT, YWT en FWT was 0.28, 0.14, 0.14 en 0.18, onderskeidelik. Die maternale permanente omgewingskomponent te wyte aan die moeder het 3 – 7 % van die totale fenotipiese variansie van die eiensk appe wat oorweeg is, bygedra. Die ooreenstemmen, Mellon Foundation

Merino sheep are an important resource for South Afric an farmers, providing meat and wool and thus an important income source. Indigenous and locally developed breeds are an important asset for many reasons, but particularly because, over time, they have developed unique combinations of adaptive traits to respond to the pressures of the local environment. To be able to distinguish between breeds for conservation and utilization purposes, the genetic variability, population structure and phylogenetic relationships were determined. Seven different Merino genotypes were sampled. These included the Dormer, SA Merino, SA Mutton Merino, Landsheep, Letelle, Dohne and Afrino. The indigenous and locally developed breeds comprised of the Damara, Pedi, Blinkhaar Ronderib Afrikaner, Blackhead Persian, Blackhead Speckled Persian, Redhead Persian, Redhead Speckled Persian, Zulu, Namaqua Afrikaner, Karakul, Swazi, Van Rooy and Dorper. The Merino, indigenous and locally developed breeds were assessed for genetic diversity using 24 microsatellites. Different statistical analyses were performed to determine the genetic variation, genetic relationships and genetic differentiation of the breeds. The SA Merino showed a high number of very distinct alleles. This study confirmed a higher variability of the SA Merino when compared with the other breeds. The genetic distance between the SA Merino and SA Mutton Merino, both fine wool breeds, was high indicating that these two breeds are relatively distant from each other. The Afrino known to have 25% SA Merino, 25% Ronderib Afrikaner and 50% SA Mutton Merino, indicated a closer relationship with the SA Mutton Merino. This result confirmed the development of the breed. From the phylogenetic analysis between the seven Merino genotypes, when compared to the other estimates obtained in the study, it was evident that the Merino genotypes in South Africa have more within breed variation than between breed variation. The genetic distance estimates

English: Genetic parameters may well aid the prediction of selection and correlated response when selection is based on production traits. The animal model, fitting an additional random factor such as the permanent maternal environmental effect is common practice to increase the accuracy of estimates. As selection in a beef breed such as the Nguni takes place in various environmental conditions, the inclusion of an additional random factor i.e. herd-year-season x sire interaction seems justified. Production traits analyzed included records of birth weight (BW), weaning weight (WW), yearling weight (YW) and eighteen-month weight (EW). Herd-year-season, sex, age at recording (except BW) and age of dam had a significant effect. Herd-year-season x sire interaction (HYSxS) was included as an additional random factor. Estimates obtained by univariate analyses were used as starting values in the multivariate analyses. In multivariate analyses another data set was used which included only herds linked with at least two other herds through sires used. This data set was also used in two bivariate analyses being the analyses between the maternally influenced traits (BWand WW) and WW and YW to gain knowledge as to a possible carry-over effect of the maternal genetic effect. Genetic trends were calculated using the regression of the average breeding value estimates . (EBV) on year of birth. Direct heritability estimates for BW, WW, YW and EW obtained by multivariate analyses were 0.31, 0.32, 0.23 and 0.27 respectively. Genetic correlations between direct and maternal effects for BW and WW were mostly low to moderate and negative (-0.35 to - 0.59 and -0.17 to -0.50 for BW and WW respectively), while direct genetic correlations among the four growth traits were moderate to high (0.51 to 0.95). The maternal genetic correlation between BW and WW was moderate (0.49). It was concluded that selection on WW alone would be undesirable as all other weights would increase. In review, breed, Afrikaans: Genetiese parameters is van kardinale belang by die voorspelling van seleksie en gekorreleerde respons wanneer seleksie vir produksie-eienskappe plaasvind. 'n Dieremodel, waarby '11 addisionele toevallige effek soos die petmanente maternale effek, ingesluit word is algemeen om die akkuraatheid van beramings te verhoog. Aangesien seleksie by vleisbeeste soos die Nguni-ras, in verskillende omgewingstoestande plaasvind, blyk die insluiting van 'n addisionele toevallige effek nl. kudde-Jaar-seisoen x vaar interaksie geregverdig te wees. Produksie-eienskappe wat gebruik is het ingesluit geboortegewig (BW), speengewig (WW), 12- maande gewig (YW) en l S-maande gewig (EW). Kudde-jaar-seisoen, geslag, ouderdom by meting (behalwe BW) en ouderdom van die moer het almal 'n betekenisvolle effek gehad. Kudde-jaarseisoen x vaar interaksie (HYSxS) is as 'n addisionele toevallige effek ingesluit. Enkeleienskap ontledings sowel as twee twee-eienskapontledings is uitgevoer en het BW en WW (eienskappe met maternale invloed) ingesluit asook WW en YW (orn die moontlikheid van 'n oordrag-effek van die maternale komponent vas te stel). Enkeleienskapwaardes is as beginwaardes in '11 veelvoudige eienskapontleding gebruik om die (ko)variansie-komponente van en/of tussen die verskillende eienskappe te beraam. Genetiese tendense is bereken deur die regressie van die gemiddelde teelwaardeberamings op jaar van geboorte. Direkte oorerflikhede vir BW, WW, YW en EW verkry deur veelvoudige-eienskapontleding was onderskeidelik 0.31, 0.32, 0.23 en 0.27. Genetiese korrelasies tussen die direkte- en maternale effek vir BW en WW was laag tot medium en negatief (-0.35 tot -0.59 en -0.17 en -0.50 vir BW en WW onderskeidelik), terwyl die direkte genetiese korrelasies tussen die vier eienskappe medium tot hoog was (0.51 tot 0.95). Die maternale genetiese korrelasies tussen BW en WW was medium (0.49). Daar is tot die gevolgtrekking gekom dat seleksie vir WW alleen ongewens sal wees aangesien alle an, National Research Foundation (NRF)

English: Genetic parameter estimates were compared usmg Gibbs sampling and REML methods. Variance components and resulting heritabilities of birth weight (BW) and weaning weight (WW) in the Elsenburg Dormer sheep stud were estimated using a conventional (REML) and a Bayesian (GIBBS sampling) approach. A sire model with relationships included were fitted in both cases. Data from 10701 lambs recorded from 1943 to 1999 were used in the analyses. Effects fitted as fixed were sex (male, female); birth status (single; twin, triplet); year (1943-1999) and age of dam (two to seven years, and older). Sire and residual were the only random effects fitted. The posterior means (h2) ofBW and WW were 0.24 and 0.15 for REML and 0.23 and 0.16 for the Bayesian method respectively. The heritability estimates obtained were of the same magnitude and in accordance with estimates found in the literature where sire models were used. Genetic parameters for the pre-wearung growth traits BW and WW were also calculated from the (eo )variance components estimated using the ASREML program by fitting univariate animal models. Log likelihood ratio tests were done to determine the appropriate mixed models. Bivariate models were also fitted for BW and WW using as starting values for the (eo)variance components the values obtained from the univariate analysis. Fixed effects fitted were the same as in the previous section. The direct heritability (h2 a) for BW and WW for the bivariate model was 0.22 and 0.12 respectively. The maternal effects (m2 ) were 0.24 and 0.11 for BW and WW respectively. These m2 values fall within the range 0.09 to 0.31 found in literature. The direct-maternal genetic correlations (ram) of -0.38 and -0.38 for BW and WW were similar to those found in literature. Genetic parameter estimates for reproduction traits, i.e. number of lambs born (NLB), number of lambs born alive (NLBA), number of lambs weaned (NL W), total weight weaned (TWW) and survival traits were obtained using, Afrikaans: Beramings van genetiese parameters IS deur van Gibbs-monstering en REMLmetodes te gebruik, vergelyk. Variansie-komponente en gevolglike oorerflikhede van geboortegewig (Ggew) en speengewig (Sgew) is in die Elsenburg-Dormerskaapstoet deur 'n konvensionele (REML) en 'n Bayes (GIBBS-monstering)-benadering beraam. 'n Vaarmodel met ingeslote verwantskappe is in beide gevalle gepas. Data van 10701 lammers, wat vanaf 1943 tot 1999 aangeteken is, is in die ontledings gebruik. Effekte wat as vas gepas is, was: geslag (manlik, vroulik); geboortestatus ( enkel, tweeling, drieling); jaar (1943-1999) en ouderdom van moeder ( twee tot sewe jaar, en ouer). Vaar en fout was die enigste toevallige effekte wat gepas is. Die posterior gemiddeldes (h2) van Ggew en Sgew was onderskeidelik 0.240 en 0.153 vir REML en 0.234 en 0.161 vir die Bayes-metode. Die oorerflikheidsberamings wat verkry is, was van dieselfde omvang en in ooreenstemming met beramings in die literatuur waar vaarmodelle gebruik is. Genetiese parameters vir die voorspeense groei-eienskappe Ggew en Sgew is ook bereken vanaf die (ko)variansie-komponente, beraam deur ASREML-deur die passing van 'n enkelveranderlike dieremodel. Log-aannneemlike verhoudingstoetse is gebruik om die geskikte gemengde modelle te bepaal. Dubbelveranderlike modelle is ook vir Ggew en Sgew gepas, deur die waardes wat van af die enkelveranderlike ontledding verkry is, as beginwaardes vir die (ko)variansie-komponente te gebruik. Vaste effekte wat gepas is, was dieselfde as in die vorige afdeling. Die direkte oorerflikheid (h2 a) vir Ggew en Sgew vir die dubbelveranderlike model was onderskeidelik 0.22 en 0.12. Die maternale oorerflikhede (m2) was onderskeidelik 0.24 en 0.11 vir Ggew en Sgew. Hierdie m2-w.aardes val binne die omvang van 0.09 - 0.31 wat in die literatuur gevind word. Direk-maternale genetiese korrelasie (ram) van -0.38 en -0.38 vir Ggew en Sgew onderskeidelik was dieselfde as dié wat in die literatuur gevind is. Genetiese pa

English: A total of 10717, 7795, and 2021 records of birth weight (BWT), weaning weight (WWT), and yearling weight (YRWT), respectively, and 1965 records of greasy (GFW) and clean fleece weight (CFW) and mean fibre diameter (MFD) were collected from the Elsenburg Mutton Merino sheep Stud and used in this study for estimation of genetic parameters and genetic and environmental trends. BWT and WWT were collected during the period 1955 to 1999 while YRWT and wool trait data were collected in the years 1983 to 1999. Eight animal models formed from ignoring or inclusion of maternal genetic and environmental effects and direct-maternal covariance were used to identify the best model for estimation of genetic parameters from both univariate and bivariate analysis. Yearly means of phenotypic performance and breeding values were used to evaluate environmental and genetic trends. Preliminary fixed model analysis showed that the fixed effects identified as having a significant (P< 0.001) effect on growth traits (BWT & WWT) were sex, birth status, age of dam and year. Year had a significant (P< 0.0001) effect on yearling weight and all fleece traits. Sex had a significant (P< 0.0001) effect on yearling weight, fleece weights and clean yield. Birth status had a significant (P< 0.0001) on yearling weight and fleece weights, and significant (P< 0.001) effect on mean fibre diameter. Age of dam had significant (P< 0.001) effect only on yearling weight. Some significant interactions were also found, but since they were very small, they were ignored. Least-squares means were 4.24 ± 0.11 for BWT, 18.7 ± 1.73 For WWT, and 51.4 ± 0.16 for YRWT; 3.37 ± 0.18 for GFW, 2.19 ± 0.12 for CFW and 23.1 ± 0.04 (µrn) for MFD. Maternal genetic, permanent environmental, and common environmental effects were important for BWT, WWT, YRWT, and GFW while maternal genetic effects also had a significant contribution to CFW. The basic direct model was adequate for MFD. Direct heritability estimates of 0.08, Afrikaans: Altesaam 10717 rekords vir geboortegewig (BWT), 7795 vir speengewig (WWT) en 2021 vir jaaroudgewig (YRWT) sowel as 1965 vir ruvaggewig (GFW), skoonvaggewig (CFW) en gemiddelde veseldikte (MFD) is verkry van die Elsenburgse Vleismerino skaapstoetery en gebruik in hierdie studie vir die beraming van genetiese parameters en genetiese- en omgewingstendense. BWT en WWT is ingesamel vanaf 1955 tot 1999 terwyl YRWT en die vageienskappe vanaf 1983 tot 1999 ingesamel is. Agt dieremodelle is gepas wat gewissel het van met en sonder maternale genetiese en omgewings effekte en is gebruik om die beste model te kies vir die beraming van genetiese parameters vanafbeide enkel- en twee-eienskapanalise. Jaarlikse gemiddeldes van fenotipiese prestasie en teelwaardes is gebruik om onderskeidelik fenotipiese en genetiese tendense te beraam. Voorlopige vastemodelanalise het getoon dat die vaste effekte met 'n betekenisvolle (P<0.0001) effek op groeieienskappe (BWT en WWT) geslag, geboortestatus, moederouderdom en jaar van geboorte is. Jaar het 'n betekenisvolle (P<0.0001) effek op jaaroudgewig en al die vageienskappe gehad. Geslag het 'n betekenisvolle (P<0.0001) effek op YRWT en vaggewigte getoon. Geboortestaat het 'n betekenisvolle (P<0.0001) invloed op YRWT, vaggewigte en MFD gehad. Moederouderdom het 'n betekenisvolle (P<0.0001) effek op YRWT getoon. Enkele betekenisvolle interaksies is ook verkry maar aangesien hulle baie klein was, is hulle geignoreer. Kleinste kwadraad gemiddeldes (kg) was 4.24 ± 0.11 vir BWT, 18.7 ± 0.16 vir YRWT, 3.37 ± 0.18 vir GFW, 2.19 ± 0.12 vir CFW en 23.1 ± 0.04 (µ) vir MFD. Maternaal-geneties-, permanente omgewing- en gemeenskaplike omgewingseffekte was belangrik vir BWT, wwr, YRWT en GFW terwyl maternale genetiese effekte ook betekenisvol tot CFW bygedra het. Die basiese model was voldoende vir MFD. Direkte oorerflikheidsberamings van 0.08, 0.04, 0.18, 0.37, 0.34 en 0.67 is verkry vir onderskeidelik BWT, WWT, YRWT, GFW, CFW en MFD. Maternale o

English: The dissertation is based on a number of separate trials conducted since 1989. The central theme is ewe rearing ability and lamb survival, and the study includes 15 papers prepared over an 11-year period from 1992 to 2002. These papers are all linked by their emphasis on sheep production as influenced by lambing and neonatal behaviour and its interface with breeding and management. The papers demonstrate the various phases the study went through, and how it eventually transpired into an account of genetic change in lamb output achievable through rigorous selection. The individual papers already contain abstracts. This summary is intended to provide readers with a broad overview of the most important outcomes of the study. The study was organised in three parts, as follows: Part 1:Background Initially, two papers provided the background for the investigations into lamb survival and ewe rearing ability. The first paper dealt with the average reproductive performance of sheep in the Southern Cape, and with levels of reproductive wastage in a number of flocks. It demonstrated that approximately one in four breeding ewes did not care for at least one lamb at lamb marking. Losses were more or less evenly distributed between barrenness and rearing failure. It was impossible to identify managerial practices conclusively associated with a good reproductive performance. Evidence was provided that an improvement in the reproduction of the current flock can be achieved by a simple method of selection that can be practiced by commercial farmers with minimal record keeping. The second paper considered rearing ability in four experimental flocks of the Merino, SA Mutton Merino and Dormer breeds. A minority of ewes was shown to contribute markedly to the observed levels of rearing failure. Animals classified as being "good" or "poor" mothers on their lamb rearing history were shown to differ in one or more pelvic dimensions in two Merino flocks and the SA Mutton Merino flo, Afrikaans: Die proefskrif is gebaseer op 'n aantal afsonderlike studies wat sedert 1989 uitgevoer is. Die onderwerp wat ondersoek is, is die grootmaakvermoë van ooie en oorlewing van lammers. Die studie sluit 15 artikels wat oor 'n l l-jaartydperk van 1992 tot 2002 geskryf is, in. Die artikels handel almaloor skaapproduksie, die invloed van gedrag tydens lam en die neonatale fase daarop, sowel as die wisselwerking daarvan met aangepaste teelten bestuurspraktyke. Die artikels dui op die fases waardeur die studie gegaan het, en hoe daar gevorder is om genetiese vordering in lamopbrengs aan te toon. Die ingeslote artikels sluit reeds Engelse opsommings in. Hierdie opsomming verskaf dus slegs 'n breë oorsig aangaande die belangrikste bevindings van die studie. Die navorsing word in drie dele opgedeel, as volg: Deel 1: Agtergrond Twee artikels het aanvanklik agtergrond verskaf vir die ondersoek van lamoorlewing en ooigrootmaakvermoë. Die eerste artikel het oor die gemiddelde reproduksie en vlakke van produksieverliese van skaapkuddes in die Suid-Kaap gehandel. Tydens merktyd is gevind dat ongeveer een uit elke vier teeltooie nie een of meer lammers versorg het nie. Verliese is ongeveer gelyk verdeel tussen onvrugbaarheid en grootmaakmislukkings. Dit was onmoontlik om bestuursfaktore wat onomstootlik aan 'n goeie reproduksietempo verwant was te identifiseer. Die artikel het aangedui dat 'n verbetering in die reproduksie van die huidige kudde bewerkstellig kan word deur 'n eenvoudige stelsel van seleksie wat met minimale rekordhouding deur kommersiële produsente toegepas kan word. The tweede artikel het die grootmaakvermoë van ooie in vier eksperimentele kuddes (Merino, SA Vleismerino en Dormer) ondersoek. 'n Minderheid ooie het grootliks bygedra tot die totale grootmaakmislukking wat waargeneem is. Ooie wat op grond van hulle produksiegeskiedenis as "goed" of "swak" geklassifiseer is, het by die Merino of SA Vleismerinokuddes ten opsigte van een of meer pelvisafmetings ve

English: A total of 150673 first lactation records of South African Holstein lactating cows were used to estimate the genetic parameters of milk (MY), butterfat (BFY), and protein (PRY) yields, and butterfat (BFP) and protein (PRP) percentages. The data comprising 113 056 dams and 1 429 sires, distributed over 1 205 herds, were collected over a period of 21 years, 1980 to 2000. The study was aimed at the following aspects: to determine the non - genetic factors influencing milk traits for use in the model for a subsequent genetic analysis; to estimate the variance-covariance components and heritabilities of all traits. Finally, to calculate the weighting factors for a selection index and predict the expected response to selection when using different milk pricing systems. Five fixed effects were defined, viz: milking frequency, age at calving, herd, month of calving and year of calving. Analysis of variance indicated that all effects were highly significant (p < 0.0001) explaining on average 64.60%, 62.96%, 64.36%, 15.66% and 23.86% of the total variation for MY, BFY, PRY, BFP and PRP, respectively. Considering the R2 and RMSE as an option, month of calving for all traits, milking frequency for BFP and PRP, and age at calving for PRP showed a minor contribution to the variation and were, thus, excluded from the model for the subsequent analysis. Heritability estimates varied from medium for BFY and PRY to high for MY, BFP and PRP. This indicates that faster genetic progress will be possible through selection of MY, BFP and PRP. The highly positive genetic correlation among yield traits indicates selection for milk yield will result in a favourable response with butterfat and protein yield. However, it will lead to an unfavourable response to selection for the percentage traits. This is due to a negative genetic correlation between milk yield with percentage traits. Using the Desire program, weighting factors and expected response per generation for milk, butterfat a, Afrikaans: 'n Totaal van 150673 eerstelaktasierekords van Suid-Afrikaanse Holsteinkoeie is gebruik om genetiese parameters van melk- (MO), bottervet- (BVO) en proteïnopbrengste (PRO) te beraam, asook bottervet- (BVP) en proteïnpersentasies (pRP). Die data wat 113 056 koeie en 1 429 vaars bevat, versprei oor 1 205 kuddes, is oor 'n periode van 21 jaar, 1980 - 2000, ingesamel. Die studie is op die volgende aspekte gerig: om die nie-genetiese faktore te bepaal wat melk-eienskappe affekteer vir gebruik in die model vir 'n genetiese ontleding; om die variansie-kovariansie komponente en oorerflikhede van alle eienskappe te beraam; en ten laaste, om die wegingsfaktore vir 'n seleksie-indeks te bereken en die verwagte responsie op seleksie wanneer verskillende melkpryssisteme gebruik word. Vyf vaste effekte is gedefinieer, nl. melkfrekwensie, ouderdom met kalwing, kudde, maand van kalwing en jaar van kalwing. Ontleding van variansie het aangetoon dat alle effekte hoogs betekenisvol (p<.0001) was, wat gemiddeld 64.6%, 62.96%, 64.36%, 15.66% en 23.86% van die totale variasie vir MO, BVO, PRO, BVP en PRP onderskeidelik verklaar het. Met R2 en RMSE as 'n opsie het maand van kalwing vir alle eienskappe, melkfrekwensie vir BVP en PRP en ouderdom met kalwing vir PRP 'n baie klein bydrae tot die variasie gemaak en is dit dus uit die model gelaat vir die volgende ontleding. Oorerflikheidsberamings het gewissel van medium vir BVO en PRO tot hoog vir MO, BVP en PRP. Dit is 'n aanduiding dat vinniger genetiese vordering moontlik sal wees deur seleksie van MO, BVP en PRP. Die hoogs positiewe korrelasie toon aan dat seleksie vir melkopbrengs 'n gunstige responsie met bottervet en proteïnopbrengs tot gevolg sal hê. Dit sal egter tot 'n ongunstige responsie lei op seleksie vir die persentasieeienskappe. Dit is te wyte aan 'n negatiewe genetiese korrelasie tussen melkopbrengs met persentasie -eienskappe. Onder die Desire-program is wegingsfaktore en verwagte responsie per generasie vir melk

English: Genetic analyses of economically important traits were carried out using data collected for 20 years (1978-1997) from a flock of Horro sheep at Bako Research Center, Ethiopia. (Co)variance components and genetic and environmental parameters were estimated for pre- and post- weaning average daily gain (ADGl, ADG2) and Kleiber ratio (KRl, KR2), birth weight (BWT), weaning weight (WWT) and bi-monthly weights to 12 months of age (WT2 to WTI2), and weight at 18 months of age (WTI8). using ASREML. Twelve models, formed with inclusion or exclusion of the maternal genetic, permanent environmental, and temporary (litter) environmental variance components and the covariance between the direct and maternal additive effect on the basic direct additive genetic model, were used. Bivariate analyses were also done. Maternal genetic and temporary environmental components were found to be important (P<0.05) sources of variation for ADG 1 and KRl while only the temporary environmental component was found to be important for ADG2 and KR2. Total heritability estimates for ADGl, ADG2, KRl and KR2, were 0.13±0.04, 0.04±0.03, 0.13±0.03, and 0.01±0.02 respectively. For weights to about six months of age, the inclusion of the temporary maternal effect in the models was found to have significant (P<0.05) contribution to the total variance. Maternal genetic components were important for weights until about eight months of age, while the direct-maternal covariance was important for BWT, WT2, WWT and ADGl. Direct genetic correlations of ADGl with BWT, WWT and WT6 were 0.04±0.21, 0.96±0.02 and 0.92±0.09 while with KRl they were -0.41±0.21, 0.74±0.10 and 0.66±O.16 respectively. The inclusion of maternal genetic, temporary and permanent environmental effects in analytical models for early weights improved model fit. Heritability estimates of average daily gains and Kleiber ratios are low to moderate. The correlations with weight traits, with the exception of BWT, are moderate to high. Thus, Afrikaans: Genetiese analises van ekonomies belangrike eienskappe is uitgevoer op data ingesamel vir 'n periode van 20 jaar (1978-1997) van 'n kudde Horro skape te Bako Navorsingssentrum, Etiopië. (Ko)variansie-komponente en omgewingsparameters is beraam vir voor- en naspeense gemiddelde daaglikse toename (GDT1 en GDT2) en Kleiberverhouding (KV1,KV2) deur gebruik te maak van ASREML. Twaalf modelle is gebruik, wat opgebou is deur in- ofuitsluiting van die maternaal genetiese permanente en tydelike (werpsel) omgewingsvariansiekomponente en die ko-variansie tussen die direken maternaal additiewe effek op die basiese direk-additiewe genetiese model. Dieselfde modelle is aangewend om die beste model te identifiseer en die belangrikheid te bereken van maternale omgewingseffekte op geboortegewig (Ggew), speengewig (Sgew) en tweemaandelikse gewigte tot 12 maande ouderdom (Gew2 tot Gew12), en gewig op 18 maande ouderdom (Gew 18). Dubbelveranderlike ontledings is gedoen tussen GDT1, GDT2, KV1 en KR2 en met Ggew, Sgew Gew6, Gew12 en Gew18. Maternaal-genetiese en tydelike omgewingskomponente het geblyk belangrike (P< 0.05) bronne van variasie vir GDT2 en KV1 te wees. Onder die beste model was direk-additiewe, maternaaladditiewe en tydelike omgewingskomponente verantwoordelik vir ongeveer 15,20 en 13 persent onderskeidelik van die totale fenotipiese variansie vir GDT1 en 9,8 en 19 persent onderskeidelik vir KV1. Vir GDT2 en KV2 was die bydrae tot die totale variansie van tydelike omgewingseffek 22 en 20 persent onderskeidelik. Totale oorerflikheidsberamings vir GDT1 en GDT2, KV1 en KV2 was 0.13 ± 0.04, 0.04±0.023, 0.13±0.03 en 0.01±0.02 onderskeidelik. Vir gewigte tot ongeveer sesmaande ouderdom is gevind dat die insluiting van die tydelike omgewingsvariansiekomponent in die modelle betekenisvolle (P< 0.05) bydrae tot die geheelvariansie gelewer het. Die permanente omgewingskomponent was betekenisvol (P< 0.05) belangrik vir Gew2 en Sgew. Maternale genetiese komponente was belang

English: A total of 4355 lamb and 4299 ewe records, obtained from Sabi sheep at Matopos Research Station from 1984 to 1994, were analysed to describe growth, carcass and reproductive traits and to investigate non-genetic factors influencing their expression. Year of birth, sex, birth/rearing status of lamb, dam age, age of lamb and slaughter age were significant sources of variation for body weights, average daily gain, carcass and reproductive traits except for exact age of lamb at 18 months, ewe age for hot and cold carcass weight. Significant (P<0.001) two-way interactions were found between year of birth and sex for pre-weaning average daily gain, 12 and 18 month weight and for birth status and sex for lamb survival. Least-squares means: 2.63 kg for birth weight; 17.2 kg for weaning weight (recorded at 120 days of age); 23.5 kg for 12 months weight; 35.7kg for 18 months weight; 124 g/day for average daily gain between birth and weaning; 21.7 kg for total weight of litter weaned and 14.6 for Kleiber ratio. Slaughter weights were low (29kg) yielding 13.6 and 13.1 kg hot and cold carcass weights respectively. Average weight of ewe at mating in May/June were 38 kg, and 35.6 kg for post-partum in October/November and 26.2 kg at weaning of lambs in February. The least squares means for reproductive traits were: 0.86,1.01,1.17,0.83,0.85 for ewes lambing to those exposed; lambs born to ewes exposed; lambs born to ewes lambing; lambs weaned to ewes exposed to the ram and lamb survival to weaning respectively. The model best describing the data were constructed and used in the subsequent analyses of (co)varaiances and heritability estimates in univariate models. Variance components of reproductive traits and lamb survival to weaning were estimated using a threshold model. The heritabilty estimates were low with 0.02, 0.06, 0.04, 0.02 and 0.04 for fertility (whether a ewe lamb or not; 0 or 1); reproductive rate (number of lambs born to a ewe exposed; 0, 1 or 2); ewe weanin, Afrikaans: Altesaam 4355 lam- en 4299 ooirekords verkry vanaf 1984 tot 1994 van Sabiskape by die Matopos Navorsingstasie is ontleed om groei-, karkas- en reproduksie-eienskappe te beskryf en om die nie-genetiese faktore wat hul uitdrukking beïnvloed te ondersoek. Geboortejaar, geslag, geboorte/grootmaakstatus van lam, moeder- , lam- en slagouderdom was betekenisvolle bronne van variasie vir liggaamsgewigte, gemiddelde daaglikse toename, karkas- en reproduksie-eienskappe, behalwe vir lamouderdom op 18 maande en moederouderdom vir warm en koue karkasgewig. Betekenisvolle ( P< 0.001) tweerigting-interaksies is gevind tussen geboortejaar en geslag vir voorspeense gemiddelde daaglikse toename, 12 en 18 maande gewig en vir geboortestatus en geslag vir lamoorlewing. Kleinste kwadraatgemiddeldes was: 2.63 kg vir geboortegewig, 17.2 kg vir speengewig (geneem op 120 dae ouderdom) 23.5 kg vir 12 maande gewig, 35.7 kg vir 18 maande gewig, 124 g/dag vir gemiddelde daaglikse toename tussen geboorte en speen, 21.7 kg vir totale gewig lammers gespeen en 14.6 vir Kleiberverhouding. Slaggewigte was laag (29 kg) met "n opbrengs van gemiddeld 13.6 kg en 13.1 kg warm en koue karkasgewigte onderskeidelik. Gemiddelde ooigewig met paring in Mei/Junie was 38 kg en 35.6 kg vir na-geboorte in Oktober/November en 26.2 kg by speen van lammers in Februarie. Die kleinste kwadraatgemiddeldes vir reproduksie-eienskappe was: 0.86, 1.01, 1.17, 0.83, 0.85 vir ooie gelam teenoor ooie by ram, lammers gebore teenoor ooie by ram, lammers gebore teenoor ooie gelam, lammers gespeen teenoor ooie by ram en lamoorlewing tot speen onderskeidelik. Die model wat die data ten beste beskryf het is opgestel en gebruik in daaropvolgende ontledings van (ko) variansies en oorerflikheidsberamings in enkel-eienskap modelle. Variansie-komponente van reproduksie-eienskappe en lamoorlewing tot speen is bepaal deur 'n drumpelmodel te gebruik. Die oorerflikheidsberamings was laag, met 0.02, 0.06, 0.04, 0.02 en 0.04 vir vrugba, International Livestock Research Institute

English: Body size and shape are objectively described using body measurements in beef cattle. How these measures of size and shape relate to the functioning of the individual is of paramount importance to livestock producers. Changes in these parameters that lead to inefficient animals are never welcomed by farmers. Therefore, constant checks on the relationships between body measurements and performance traits are vital in selection programs. To estimate heritabilities and genetic correlations among body measurements and growth traits, data of 7 266 performance records of Bonsmara bull calves participating in on-farm growth tests (Phase D) were used. The data set was extracted from the Integrated Registration and Genetic Information System (INTERGIS) of South Africa. The data covered a 25-year period i.e. from 1972 - 1996. Data were recorded from 45 herds, with 439 sires and 5 180 dams involved. Traits analyzed were scrotal circumference (SC), body length (BL), shoulder height (SH), birth weight (BW), weaning weight (WW), final weight (FW) and average daily gain (ADG) from weaning to final test date. Multivariate REML methodology was used to estimate (co)variances and genetic components for different traits. In cases where there were more than one value for an estimate, the values were pooled, weighting each estimate by the inverse of its sampling variance. Different models were, however, fitted for each trait. The permanent environmental effect was found to be important for most of the post-weaning traits, but it could, however, not be considered in the multivariate runs. This was due to computational limitations imposed by the data set. A simple model considering only direct animal effect and random error was fitted for all post-weaning traits. Heritability estimates for body measurements ranged from medium for body length (0.27±0.05) to high for shoulder height (0.42±0.05) and scrotal circumference (0.46±0.06). Corresponding estimates for performance traits wer, Afrikaans: Liggaamsgrootte en -vorm van vleisbeeste kan objektief beskryf word m.b.v. liggaamsmates. Die verband tussen hierdie mates en die funksionering van die dier is van groot belang vir produsente. Veranderinge in hierdie parameters wat lei tot oneffektiewe diere sal nie deur boere verwelkom word nie. Dit is dus nodig om die verband tussen liggaamsmates en produksie eienskappe te monitor in seleksieprogramme. Oorerfbaarhede en genetiese korrelasies tussen liggaamsmates en groei eienskappe is bepaal. Produksierekords van 7 266 Bonsmara bulkalwers, afkomstig van 45 kuddes, met 439 vaders en 5 180 moeders, wat in op-die-plaas groeitoetse (Fase D) deelgeneem het, is gebruik. Die data was afkomstig van die geïntegreerde registrasie en genetiese informasie sisteem (INTERCIS) van Suid-Afrika en strek oor 'n 25 jaar periode (1972 tot 1996). Eienskappe wat bestudeer is sluit in skrotumomvang (SC), liggaamslengte (BL), skouerhoogte (SH), geboortegewig (BW), speengewig (WW), finale gewig (FW) en gemiddelde daaglikse toename (ADC). Meereienskap REML metodologie is gebruik om (ko)variansie komponente te beraam vir die verskillende eienskappe. In gevalle waar daar meer as een beramer vir 'n komponent was, is die waardes gepoel en geweeg deur die invers van die variansie. Verskillende modelle is vir elke eienskap gepas. Volgens enkeleienskap analises was die permanente omgewings effek belangrik vir meeste van die na-speense eienskappe, maar dit kon nie in ag geneem word in die meereienskap lopies nie, weens rekenaarbeperkings veroorsaak deur die grootte van die datastel. 'n Eenvoudige model wat slegs die direkte effek en toevallige fout komponent in ag neem, is gepas vir alle na-speense eienskappe. Oorerftikhede vir liggaamsmates varieer van medium vir liggaamslengte (0.27±0.05) tot hoog vir skouerhoogte (0.42±0.05) en skrotumomvang (0.46±0.06). Ooreenstemmende beramers vir produksie eienskappe is: direkte (0.31±0.05) en maternale geboortegewig (0.10±0.03), direkte (0.29±0.0, Professional Development Program