A sound breeding objective is the basis for genetic improvement in overall economic
merit of animals. Breeding objectives for Holstein and Jersey dairy cattle breeds in South
Africa were developed in the current study, using a systematic approach. First, a logical
framework with a profit focus was utilised to develop plausible selection goals for the
pasture-based and concentrate-fed dairy production systems in South Africa, leading to
an exhaustive list of objective traits influencing these goals and subsequently their
possible selection criteria. Next, economic values were calculated for those objective
traits for which there was adequate bio-economic data, viz.: milk volume, fat yield,
protein yield, live weight, longevity, calving interval and somatic cell score. A bioeconomic
model, simulating typical South African pasture-based and concentrate-fed
herds, was used to calculate economic values by determining changes in profit arising
from an independent unit increase in each trait. Alternative payment systems of four
major milk buyers in South Africa were used. Relative economic values, standardised to
the value of protein, were used to compare the relative importance of traits across breeds,
production systems and payment systems. Protein yield, fat yield and longevity
consistently had positive economic values and the converse was true for body weight and
calving interval. Economic value for volume was positive or negative, depending on
whether the payment system paid for it or did not. Economic values were reasonably
robust to fluctuations in the cost of feed and price of beef; with the exception of fat,
whose value became negative beyond the feed price of ZAR3.50. Protein was, overall,
the most important trait, although volume, live weight, longevity and somatic cell score were more important in some situations. Calving interval was the least important trait, its
value ranging from 4 to 22% compared to that of protein, probably because the model
used underestimated its value. Sire rankings on aggregate EBVs based on these
economic values did not differ much across breeds, production systems and payment
systems, most rank correlations falling in the range 0.70-0.99. A single breeding
objective may therefore be used for both the Holstein and Jersey breeds, across the
different production and payment systems. The basis for multiple-trait selection in the
major cattle breeds in South Africa has thus been developed. Considerable work,
however, needs to be done to enhance this breeding objective as well as facilitate its wide
adoption by industry.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-11162010-160816 |
| Date | 16 November 2010 |
| Creators | Banga, Cuthbert Baldwin |
| Contributors | Dr J van der Westhuizen, Prof DJ Garrick, Prof FWC Neser |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-11162010-160816/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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