Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The objective of this study was to obtain more information regarding the characterisation of
Afrikaner (A), Hereford (H) and Simmentaler (S) breeds in an initial crossbreeding programme and
subsequent composite development. This involves the estimation of breed additive effects, breed
maternal, individual heterotic effects and maternal heterotic effects in the initial crossbreeding
phase and the estimation of genetic parameters and prediction of breeding values in later
generations for birth weight (BW), weaning weight (WW) and cow efficiency (CE; WW/dam
weight" 75 x 100) in an intensive environment under high stocking rates.
In the analysis of the initial crossbreeding phase, the S breed direct effects, expressed as deviation
from the general mean, were positive (P :s; 0.01) for both BW and WW. Hereford and A breed direct
effects were negative (P :s; 0.01) for both BW and WW. Afrikaner direct maternal effects were
positive (P :s; 0.01) for both BW and WW. The H direct maternal effect was negative (P :s; 0.05) (-
2.8%) for WW. Simmentaler maternal effect was negative (P :s; 0.01) for BW but non-significant (P
;:::0:.05) for WW. Individual heterotic effects for BW were significant (P:S; 0.01) in H x S (3.5%)
and S x A (11.0%) only. Individual heterotic effects were positive (P :s; 0.01) for WW, with that of
the H x A (9.8%) and S x A (6.7%) crosses exceeding the H x S (3.1%) cross. Maternal heterotic
effects were non-significant (P ;:::0:.05) for both BW and WW.
Investigations of the contributions of the A, Hand S during composite development in later
generations, respectively, were made to estimate direct heritabilities (h2
a) and maternal heritabilities
(h2 m) for BW and WW of the calf and CE of the dam. Calves were born between 1968 and 1993 (n
= 52628). Calves of this composite population had varying levels of A, Hand S genes ranging from
o to 75%, 0 to 100% and 0 to 96.9%, with an average of 4.3,19.3 and 33.4%, respectively. For the A, direct heritabilities fitting unitrait models were 0.67, 0.53 and 0.19 for BW, WW and CE,
respectively, with corresponding estimates of h2mbeing 0.22, 0.36 and 0.58. Genetic correlations
between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to -
0.62. Direct breeding values for BW increased and reached a maximum value at 0.11 proportion of
A. The maternal breeding values for BW decreased linearly between 1.6 to 37.5% A proportion and
increased linearly between 37.5 to 75% A proportion. For WW, the direct breeding values
decreased linearly with increasing A proportion, while the maternal breeding values were not
affected by proportion of A. Cow efficiency was unaffected by an increase in proportion of A.
For the H, direct heritabilities fitting unitrait models were 0.67,0.52 and 0.21 for BW, WW and CE,
respectively, with corresponding estimates of h2mbeing 0.22, 0.36 and 0.60. Genetic correlations
between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to -
0.64. Direct breeding values and maternal breeding values for BW and WW decreased with
increasing proportion of H. Direct breeding value for CE increased, while the maternal breeding
value for CE reached minimum value at 0.62 proportion ofH.
For the S, direct heritabilities fitting unitrait models were 0.66, 0.53 and 0.21 for BW, WW and CE,
respectively, with corresponding estimates of h2m being 0.22, 0.36 and 0.59. Genetic correlations
between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to -
0.63. Direct breeding values for BW and WW decreased and maternal breeding values increased
with increasing proportion of S. Cow efficiency was unaffected by an increase in proportion of S.
The study suggests that in the initial crossbreeding phase, purebred S breeding seems to be the best
breeding practice for this environment and that during composite development, high A and H
contributions could lead to low BW and WW (except the maternal contribution of the A for BW
and WW). The advantage of the S lies more in the maternal contribution than in the direct
contribution suggesting that the S is a large-framed maternal line rather than a terminal sire line. / AFRIKAANSE OPSOMMING: 'N WAARDEBEP ALING VAN DIE BYDRAE VAN DIE AFRIKANER,
SIMMENTALER EN HEREFORD TYDENS KOMPOSIETE RASONTWIKKELING
BY VLEISBEESTE: Die doel van die studie was om inligting aangaande die karakterisering van die Afrikaner (A),
Hereford (H) en Simmentaler (S) rasse tydens die oorspronklike aanvangsfase van kruisteling en
daaropvolgende komposiet ontwikkeling te verkry. Dit het die beraming van direkte additiewe,
individuele heterose, direkte materne en materne heterotiese effekte tydens die aanvangsfase van
die kruisteeltprogram, die beraming van genetiese parameters en die voorspelling van die
teeltwaardes in latere generasies behels. Die eienskappe wat ingesluit is, is geboortegewig (BW),
speengewig (WW) en koeidoeltreffendheid (CE; WW/koeigewigo.75
). Hierdie kudde is in 'n
intensiewe maar onder 'n hoë weidingsdruk omgewing aangehou.
Tydens die ontleding van die eerste kruisteeltfase is die direkte additiewe effekte vir die S,
uitgedruk as afwyking van die algemene gemiddelde, vir beide BW en WW positief (P ~ 0.01).
Direkte additiewe effekte vir die H en A was vir beide BW en WW negatief (P ~ 0.01). Afrikaner
materne effekte was vir beide BW en WW (P ~ 0.01) positief. Die H direkte materne effekte was
negatief (-2.8%) (P ~ 0.05) vir WW. Simmentaler maternal effekte was ook vir BW negatief (P
~ 0.01), maar nie-betekenisvol (P 20.05) vir WW. Individuele heterose was slegs betekenisvol (P
~ 0.01) vir kombinasies van H x S (3.5%) en S x H (11.0%) vir BW. Individuele heterose was
positief (P ~ 0.01) vir WW waar H x A (9.8%) en S x A (6.7%) kruisings dié van die H x S (3.1%)
kruising oortrefhet. Materne heterose was vir beide BW en WW nie-betekenisvol (P 2 0.05).
Die relatiewe bydraes van die A, H en S is ook tydens komposiet-ontwikkeling bereken. Direkte
additiewe oorerflikhede (h2 a) en materne oorerflikhede (h2m) is vir BW en WW van die kalf en CE
van die koei beraam. Kalwers in die komposiet kudde, gebore tussen 1968 en 1993 (n = 52628), het
variërende vlakke van A, H en S gene. Die samestelling het gevarieer van 0 - 75%, 0 - 100% en 0 -
96.9%, met 'n gemiddeld van 4.3, 19.3 en 33.4%. Vir die A was die direkte erfbaarhede (h2 a), soos deur die passing van 'n enkeleienskapmodel
beraam, 0.67, 0.53 en 0.19 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings
van 0.22, 0.36 en 0.58 vir h2
rn- Genetiese korrelasies tussen direkte en mateme effekte (ram)was
almal negatief en het tussen -0.32 en -0.62 gewissel. Direkte teelwaardes vir BW het met
toenemende A-bydrae gestyg en het 'n maksimum waarde by 0.11 bereik. Die mateme teelwaardes
vir BW het lineêr gedaal tussen 1.6 en 37.5% A-bydrae en het weer lineêr tussen 37.5 en 75% Abydrae
gestyg. Vir WW het die direkte teelwaardes lineêr met toenemende A-bydrae gestyg, terwyl
die mateme teelwaardes nie deur A-bydrae beïnvloed was nie. Koeidoeltreffendheid was nie deur 'n
toename in A-bydrae beïnvloed nie.
Vir die H was die direkte erfbaarhede (h2 a), soos deur die passing van 'n enkeleienskapmodel
beraam 0.67, 0.52 en 0.21 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings
van 0.22, 0.36 en 0.60 vir h2 rn- Genetiese korrelasies tussen direkte en mateme effekte (ram)was
almal negatief en het tussen -0.32 en -0.64 gewissel. Direkte teelwaardes en mateme teelwaardes vir
BW en WW het met toenemende H-bydrae gedaal. Direkte teelwaarde vir CE het ook met
toenemende If-bydrae gedaal, terwyl die mateme teelwaarde 'n minimum waarde by 0.62 H-bydrae
bereik het.
Vir die S was die direkte erfbaarhede (h2a), soos deur die passing van 'n enkeleienskapmodel
beraam 0.66, 0.53 en 0.21 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings
van 0.22, 0.36 en 0.59 vir h2
m- Genetiese korrelasies tussen direkte en mateme effekte (ram)was
almal negatief en het tussen -0.32 en -0.63 gewissel. Direkte teelwaardes vir BW en WW het
gedaal, terwyl die mateme teelwaardes met toenemende S-bydrae gestyg het. Koeidoeltreffendheid
was nie deur 'n toename in S-bydrae beïnvloed nie.
Die bevinding was dat tydens die ontleding van die eerste kruisteeltfase die teling van suiwer S
aanbeveel word en dat tydens komposiete-ontwikkeling toenemende A- en H-bydraes neig om
aanleiding te gee tot afnames in BW en WW (behalwe die mateme bydrae van die A vir BW en
WW). Die S-bydrae se voordeel is meer in die mateme bydrae as in die direkte bydrae geleë en dui
dus aan dat die S as 'n mateme grootraam lyn i.p.v. as 'n terminale bullyn gebruik moet word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51591 |
| Date | 12 1900 |
| Creators | Skrypzeck, Heidi |
| Contributors | Schoeman, S. J., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 88 p. : ill. |
| Rights | Stellenbosch University |
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