Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Profitable milk production and genetic improvement in dairy herds are largely dependant on fertile
cows capable of calving down on an annual basis. Several studies indicate declines in the
reproductive performance of Holstein cows over the last 30 years. Calving interval (CI) and services
per conception (SPC) are being used by dairy farmers as indicators of the reproductive performance
of dairy cows. However, using these traits as cow fertility indicators is problematic as CI is dependent
on subsequent calving dates while SPC is strongly linked to inseminator proficiency. The aim of the
study is therefore, firstly, to describe alternative fertility traits derived from insemination and calving
dates and pregnancy check results. The effects of some non-genetic factors on these traits are
discussed. Means±sd for interval traits from calving to first insemination (CFS) and the interval from
calving to conception (DO) were respectively 77±30 and 134±74 days while the number of services
per conception (SPC) averaged 2.55±1.79. The percentage of first servics occurring within 80 days
post-partum (FS80d) and the proportion of cows being confirmed pregnant within 100 (PD100d) and
200 days post-partum (PD200d) were 0.64±0.48, 0.36±0.48 and 0.71±0.45, respectively. Although
fertility traits were affected significantly by lactation number, calving year and month, herds
(managers) had the largest effect.
Fertility is a complex trait, however, the challenge is finding traits that best describe this trait. Genetic
parameters for these traits could give an indication of the response to selection in dairy herds. In the
second part of this study, genetic parameters and correlations between fertility traits, sourced from
standard reproduction management data bases, are analysed for Holstein cows using bivariate linearlinear
and linear-threshold animal models. Insemination events (n = 69 181) from 26 645 lactations of
9 046 Holstein cows from 14 herds, calving down during the period from 1991 to 2007, were
available. The outcome of each AI event was known. Insemination records were linked to the calving
date of each cow, lactation number as well as dam and sire identification. Fertility traits indicating the
ability of cows to show heat early in the breeding period, and to become pregnant, were derived. Data were analysed using bivariate linear-linear and linear-threshold animal models with fixed effects being
herd (14 levels), year (17 levels), season (4 levels) and lactation number (6 levels). The model
included the random effects of animal and animal permanent environment (PE). Heritability estimates
ranged from 0.04±0.01 to 0.10±0.02 for FS80d, from 0.07±0.01 to 0.08±0.02 for PD100d and from
0.06±0.04 to 0.08±0.02 for PD200d depending on the two-trait combination. Although heritability
estimates of most fertility traits were below 0.10, they were in close agreement with results published
by other researchers using linear models. Genetic correlations between different fertility parameters
analyzed in this study indicated that it is unlikely that a single characteristic would serve well for
selection purposes; instead, combining different traits could be used in selection programmes to
improve fertility. Further research in constructing an optimal fertility index is warranted.
In the third part of this study, genetic parameters for South African Holstein cows for fertility and
production traits were estimated from 2415 lactation records. Two-trait analysis of fertility and milk
yield was investigated as a method to estimate fertility breeding values when culling, or selection
based on milk yield in early lactation, determines presence or absence of fertility observations in later
lactations. Fertility traits were days from calving to first service (CFS), days from calving to conception
(DO), percentage cows inseminated within 80d post-partum (FS80d), number of service per
conception (SPC), and the binary traits percentage of cows pregnant within 100d and 200d postpartum
(PD100d, Pd200d). Milk production traits were 300 day milk, fat and protein yield. For fertility
traits, range of estimates of heritability (h2) was 0.006 to 0.08 for linear traits and 0.05 to 0.12 for
binary traits. The range for permanent environmental variance (c2) was 0.016 to 0.032. In this study
genetic correlations of fertility with milk production traits were unfavourable ranging between −0.93 to 0.76. / AFRIKAANSE OPSOMMING: Winsgewende melkproduksie en genetiese verbetering in melkkuddes hang grootliks af van vrugbare
koeie wat op ‘n jaarlikse basis kalf. Verskeie studies toon dat die reproduksievermoë van
Holsteinkoeie oor die afgelope 30 jaar afgeneem het. Melkboere gebruik tussenkalfperiode (TKP) en
aantal inseminasies per konsepsie (KIPK) as aanduidings van die reproduksievermoë van melkkoeie.
Dit is egter moeilik om hierdie eienskappe as vrugbaarheidseienskappe vir melkkoeie te gebruik
omdat TKP afhanklik is van opeenvolgende kalfdatums terwyl KIPK baie sterk gekoppel is aan die
inseminasievermoë van die insemineerders. In die eerste gedeelte van die studie word alternatiewe
vrugbaarheidseienskappe, wat afgelei is van inseminasie- en kalfdatums en die uitslag van
dragtigheidsondersoeke, beskryf. Die invloed van ‘n aantal nie-genetiese faktore op dié eienskappe
word ook bespreek. Gemiddeldes±standaard afwykings vir die periode vanaf kalwing tot eerste
inseminasie (CFS), die periode van kalwing tot konsepsie (DO) was 77±30 en 134±74 dae
onderskeidelik, terwyl die aantal inseminasies per konsepsie (SPC) 2.55±1.79 was. Die persentasie
eerste inseminasies wat binne 80 dae na kalwing (FS80d), en die persentasie koeie wat dragtig
bevestig is binne 100 (PD100d) en 200 dae na kalwing (PD200d) was 0.64±0.48, 0.36±0.48 en
0.71±0.45, onderskeidelik. Hoewel vrugbaarheidseienskappe betekenisvol beïnvloed is deur
laktasienommer, jaar en seisoen van kalwing, het kuddes (bestuurders) die grootste effek op
eienskappe gehad.
Vrugbaarheid is ‘n ingewikkelde eienskap en die uitdaging is om eienskappe te vind wat dit die beste
beskryf. Genetiese parameters vir eienskappe wat oorweeg word sal ‘n aanduiding gee van die
seleksieresponse in melkkuddes. In die tweede gedeelte van die studie is genetiese parameters van
vrugbaarheidseienskappe en korrelasies tussen dié eienskappe beraam. Eienskappe is bekom vanaf
reproduksiebestuursprogramme wat in melkkuddes gebruik word. Al die inseminasierekords (n =
69 181) van 26 645 laktasies van 9 046 Holsteinkoeie van 14 melkkuddes wat tussen 1991 en 2007 gekalf het, was beskikbaar. Die uitslag van elke inseminasie was bekend. Inseminasierekords is met
die kalfdatum, laktasienommer, identifkasienommers van die moeder en vader van elke koei,
gekoppel. Vrugbaarheidseienskappe wat die vermoë van koeie aandui om vroeg na kalwing op hitte
te kom en beset te raak, is verkry. Die data is ontleed deur gebruik te maak van twee-eienskap liniêreliniêr-
en liniêr-drempel-diere modelle met vaste effekte kudde (14 vlakke), jaar (17 vlakke), siesoen (4
vlakke) en laktasienommer (6 vlakke). Die modelle het die ewekansige effekte van dier- en dierpermananente
omgewingseffkte (PE) ingesluit. Genetiese, diere PE en residuele korrelasies is
vervolgens beraam. Oorerflikhede varieer vanaf 0.04±0.01 tot 0.10±0.02 vir FS80d, vanaf 0.07±0.01
tot 0.08±0.02 vir PD100d en vanaf 0.06±0.04 tot 0.08±0.02 vir PD200d, afhangende van die tweeeienskap
kombinasie. Ten spyte daarvan dat die oorerflikhede van die meeste vrugbaarseienskappe
laer as 0.10 is, is die resultate in ooreenstemming met ander navorsers wat liniëre modelle gebruik
het. Genetiese korrelasies tussen verskillende vrugbaarheidseienskappe toon dat daar nie enkel
beste eienskap is wat vir seleksiedoeleindes gebruik kan word nie. Dit sou waarskynlik beter wees om
verskillende eienskappe te kombineer om die vrugbaarheid in melkkoeie te verbeter. Verdere
navorsing is nodig om ‘n optimale vrugbaarheidseienskap te ontwikkel.
Dit is belangrik dat die verband tussen reproduksie en melkproduksie vir melkkoeie bepaal word. In
die derde gedeelte van die studie is genetiese parameters vir vrugbaarheid- en melkproduksieeienskappe
vir Suid Afrikaanse Holsteinkoeie beraam. ‘n Totaal van 2415 laktasierekords was
beskikbaar. Vrugbaarheid en melkproduksie is volgens ‘n twee-eienskap analise ontleed as ‘n metode
om teelwaardes vir vrugbaarheid te bepaal in gevalle waar die uitskot of seleksie gebaseer op
melkproduksie in vroeglaktasie die teenwoordigheid of afwesigheid van vrugbaarheidseienskappe in
latere laktasies bepaal. Vrugbaarheidseienskappe was die periode (aantal dae) tussen kalfdatum en
eerste inseminasie (CFS), die aantal dae van kalf tot konsepsie (DO), die persentasie koeie wat by 80
dae na kalf vir die eerste keer geïnsemineer was (FS80d), die aantal inseminasies per konsepsie
(SPC), en binêre eienskappe van die persentasie koeie wat by 100 dae en 200 dae na kalf beset was
(PD100d en PD200d). Melkproduksie-eienskappe was 300-dae melk., vet- en proteïnproduksie. Vir
vrugbaarheidseienskappe het die oorerflikheidswaardes (h2) vanaf 0.006 tot 0.08 vir liniêre
eienskappe gevarieer en tussen 0.05 tot 0.12 vir binêre eienskappe. Die permanente
omgewingsvariansie (c2) het tussen 0.016 tot 0.032 gevarieer. In hierdie studie was die genetiese
korrelasies tussen vrugbaarheidseienskappe en melkproduksie-eienskappe ongunstig en het dit
tussen −0.93 tot 0.76 gevarieer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20083 |
| Date | 03 1900 |
| Creators | Potgieter, Johannes Phillipus |
| Contributors | Dzama, K., 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 | Unknown |
| Type | Thesis |
| Format | 82 p. : ill. |
| Rights | Stellenbosch University |
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