Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aim of this study was to evaluate the Simbra breed of cattle for certain non-genetic as well as
genetic parameters influencing live weight traits in the breed. Live weight traits included birth weight
(BW), weaning weight at 200 days of age (WW), yearling weight at 400 days of age (YW) and 600
day weight. The Simmental and Simbra Breeders’ Society of Southern Africa availed 148751 records
for analysis from the year 1987 till 2009. Due to deficiencies of various kinds in the data and the
restrictions imposed for the purposes of the analysis, 56.44% of the records were discarded for BW,
76.55% for WW, 91.54% for YW and 96.32% for 600-day weight.
Non-genetic parameters affecting BW, WW, YW and 600-day weight were analysed using the
General Linear Models procedure of the Statistical Analysis System (SAS, 2004) software. During
this procedure sex of calf, breed composition of calf, breeder of calf, month of birth, year of birth and
dam age were fitted in the models. BW, WW, YW and Mature Cow Weight (MCW) were fitted as
covariates where possible. It was determined that the fixed effects of sex, dam age, breeder, year
and month had a significant (P < 0.05) effect of BW and WW while dam age was not significant (P >
0.05) for YW or 600-day weight. Breed was found non significant for YW. Breeder of the calf
accounted for the most variation in BW, WW, YW as well as 600-day weight with a contribution of
17.55%, 25.77%, 18.35% and 10.71% respectively. Tukey’s multiple range tests were performed for
testing differences between least square means. Results indicated male calves to be significantly
heavier than females for all four traits measured. Breed composition differences were found
significant until WW. Calves with higher Brahman percentage weighted more at birth while calves with
higher Simmental percentage weighed more at weaning. Middle-aged dams were found to account
for heavier calves at both BW and WW while very young dams and very old dams produced lighter
calves for the two live weight traits. A number of years showed a significant difference from each
other for all the traits measured as well as month of birth.
(Co) variance components and the resulting genetic parameters were estimated using single-traits
and three-traits analysis by means of Restricted Maximum Likelihood procedures (Gilmour et al., 2002). Appropriate models were selected by means of Log likelihood ratios tests and implemented to
estimate genetic parameters for each of the traits studied. Direct additive heritabilities for BW, WW,
YW and 600-day weight in the Simbra were respectively 0.56 ± 0.08, 0.67 ± 0.09, 0.70 ± 0.11 and
0.10 ± 0.03 when the most suitable animal model was fitted in single-trait analyses for each trait.
Single traits analysis also included maternal additive as well as the correlation between direct additive
and maternal additive for BW, WW and YW. Maternal additive heritability estimates of 0.24 ± 0.07,
0.33 ± 0.06 and 0.38 ± 0.07 was obtained for BW, WW and YW. Correlation estimates between direct
additive and maternal additive were -0.75 ± 0.07, -0.93 ± 0.07 and -0.85 ± 0.08 for BW, WW and YW
respectively. Furthermore, dam permanent environment was included as an additional random effect
that increased the log likelihood value significantly. A value of 0.04 ± 0.05 was obtained for dam
permanent environment estimate for WW. When a three traits analysis was done for the same traits,
but using a significantly smaller data set, direct additive heritabilities of 0.24 ± 0.07 for BW, 0.33 ±
0.06 for WW and 0.38 ± 0.07 for YW were obtained. Genetic and environmental correlation estimates
of 0.18 ± 0.16 and 0.09 ± 0.06 between BW and WW; 0.27 ± 0.16 and 0.07 ± 0.06 between BW and
YW; as well as 0.52 ± 0.10 and 0.45 ± 0.05 between WW and YW were obtained during the three-trait
analysis. The magnitude of the heritabilities obtained in this study indicates that the opportunity exists to make genetic progress through proper selection objectives. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die Simbra bees ras te evalueer op grond van sekere niegenetiese
so wel as genetiese parameters wat lewende gewig beïnvloed. Gereelde en akkurate
opnames van lewende gewig, is ‘n goeie indikasie van groei potensiaal en is ‘n minimim vereiste vir
meeste beesras telings genootskappe. Lewende gewigs eienskappe sluit in geboorte gewig (BW),
speen gewig gemeet op 200 dae (WW), jaaroue gewig gemeet op 400 dae (YW) en finale gewig
gemeet op 600-dag gewig. Die Simmentaler en Simbra genootskap van Suid Afrika het 148751
rekords beskikbaar gestel vir evaluasie vanaf die jaar 1987 tot 2009. Daar was egter groot tekort
komings aan die gewewe data en dus is daar 56.44% van die rekords vir BW nie gebruik nie, 76.55%
vir WW, 91.54% vir YW en 96.32% vir 600-dag gewig.
Nie-genetiese parameters wat die onderskeie lewende gewigte beïnvloed het, is geanaliseer deur
Algemene Lineêre Modelle met behulp van die Statistiese Analitiese Sisteem (SAS, 2004) sagteware.
Gedurende die analise is geslag van die kalf, ras samestelling, teler van die kalf, maand van
geboorte, jaar van geboorte asook moeder ouderdom gepas in die modelle vir die onderskeie
gewigte. Geboorte gewig, speen gewig, jaaroue gewig asook volwasse koei gewig is gepas in elk
van die modelle as ko-variate. Volgens die resutate is daar vasgestel dat geslag van die kalf, moeder
ouderdom, teler, jaar, maand en volwasse koei gewig almal ‘n betekenisvolle (P < 0.05) invloed
gehad het op BW en WW. Die moederouderdom was nie betekenisvol (P > 0.05) vir YW of 600-dag
gewig nie. Die ras samestelling was ook nie betekenisvol gevind vir YW. Teler van die kalf was
verantwoordelik vir die meeste variasie in BW, WW, YW asook 600-dag gewig met ‘n bydrae van
17.55%, 25.77%, 18.35% en 10.71% onderskeidelik. Tukey se veelvuldige vergelykings toets is
gebruik om onderskeid te tref tussen “least square means”. Resultate het aangedui dat manlike diere
swaarder weeg as vroulike diere tot en met finale gewig. Ras samestelling vir BW en WW was
betekenisvol verskillend vir die diere. Kalwers met ‘n hoër Brahmaan persentasie het swaarder BW
opgelewer as dié met ‘n hoër Simmentaler persentasie, terwyl kalwers met ‘n hoër Simmentaler
persentasie swaarder geweeg het met speen en dus ideal is vir speen kalwer produksie stelsels.
Middel-jarige moeders het swaarder kalwers geproduseer met geboorte en speen as baie jong en -
ou moeders. Sommige jare waarin van die kalwers gebore is, het ook betekenisvol van mekaar
verskil asook die maand waarin die kalf gebore is. Ko) variansie faktore en opeenvolgende genetiese parameters is bepaal met behulp van enkeleienskap
analises asook meervuldige-eienskap analises deur middel van die “Restricted Maximum
Likelihood” prosedure (Gilmour et al., 2002). Modelle is opgestel vir elk van die gewigte deur die
geskikte genetiese terme toe te voeg en te toets met behulp van “Log likelihood tests” om sodoende
die onderskeie genetiese parameters te bepaal. Direkte genetiese oorerflikhede bepaal deur enkeleienskap
analises vir die Simbra ras was as volg, 0.56 ± 0.08 vir BW, 0.67 ± 0.09 vir WW, 0.70 ± 0.11
vir YW en 0.10 ± 0.03 vir 600-dag gewig. Die direkte maternale genetiese oorerflikhede tydens
dieselfde enkel-eienskap analise vir die onderkeie gewigte was 0.24 ± 0.07 vir BW, 0.33 ± 0.06 vir
WW en 0.38 ± 0.07 vir YW. Korrelasies tussen direkt genetiese en direk maternale eienskappe was
sterk negatief. ‘n Waarde van -0.75 ± 0.07 is bepaal vir BW, -0.93 ± 0.07 vir WW en -0.85 ± 0.08 vir
YW. ‘n Adisionele faktor was ook ingelsuit vir WW, naamlik die permanente omgewing van die
moeder, wat ‘n waarde opgelewer het van 0.04 ± 0.05. Tydens die veelvuldige-eienskap analise het
die oorerflikhede merkwaardig verminder vir die betrokke gewigte en kan ook waargeneem word as
die meer korrekte genetiese weergawe. Direkte genetiese oorerflikhede van 0.24 ± 0.07 vir BW, 0.33
± 0.06 vir WW en 0.38 ± 0.07 vir YW was bepaal. Hierdie matig tot hoë parameters dui op genetiese
vordering deur middel van korrekte seleksie prosedures. Genetiese- en omgewing korrelasies is ook
bepaal tydens die analise en het positiewe waardes opgelewer. ‘n Genetiese korrelasie waarde van
0.18 ± 0.16 tussen BW en WW is bepaal asook ‘n waarde van 0.27 ± 0.16 tussen BW en YW en ‘n
waarde van 0.52 ± 0.10 tussen WW en YW. Hierdie korrelasies dui daarop dat na-speengewigte
vermeerder kan word deur te selekteer vir verhoogde WW sonder om BW dramties te vermeerder.
Omgewings korrelasie waardes van 0.09 ± 0.06 tussen BW en WW, 0.07 ± 0.06 tussen BW en YW
asook ‘n waarde van 0.45 ± 0.05 tussen WW en YW is gevind. Genetiese neigings is bepaal vir die
onderskeie gewigte deur die gemiddelde voorspelde teelwaardes aan te teken teenoor elke jaar wat
bereken was tydens die enkel-eienskap analises vir die onderskeie gewigte. Groot variasie asook
negatiewe tendense vir WW en YW is ondervind van jaar tot jaar en dui daarop dat die seleksie
doelwitte vir lewendige gewig nie in plek gestel is nie en is dit nodig om te her evalueer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4168 |
| Date | 03 1900 |
| Creators | Smith, Algina Maria Johanna |
| Contributors | Dzama, K., University of Stellenbosch. Faculty of Agrisciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 69 p. : ill. |
| Rights | University of Stellenbosch |
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