Breeding programmes for Simmental beef cattle - defining the selection objective

Author
Paul L. Charteris
Institute of Veterinary, Animal & Biomedical Sciences ,
Massey University, Palmerston North, New Zealand

From: New Zealand Simmental, Volume 40, 1996. Pp. 70-71

Many livestock breeding industries are establishing selection objectives capable of producing productive and "consumer friendly" animals.

Breeding programme design

Breeding programme design is one of the most commonly discussed but poorest implemented technologies available to beef cattle breeders. Essentially a breeding programme can be thought of as the direction of, or target for, selection and the technologies used to achieve those targets. In the New Zealand beef cattle industry a common problem is the lack of clear direction given to the establishment of breeding programmes and how these programmes should focus on improving profitability and meeting requirements of beef industry participants.

The aim of genetic improvement is to increase farm profit (by increasing income, reducing costs, or both) whilst meeting customer requirements. Given a number of animals available for selection, each with Group Breedplan EBV's, the actual selection of which animals to breed remains a difficult task. Attaching weighting factors to different EBV's to derive a single dollar value for a bull would be valuable for breeders selecting animals to mate in their own herds and for selling to their commercial bull-buying customers. The use of Breedplan allows breeders to identify genetically superior animals for some economically important traits, in this respect Breedplan is a valuable tool for beef cattle breeders and their bull-buying customers. However, the use of Breedplan should be considered a means to an end, and not the end itself.

A sequential procedure for the development of a breeding program should incorporate the following five steps (Ponzoni, 1989):

1. Definition of the selection objective. This is a statement of direction for the breeding programme. The selection objective is simply a statement (model) describing the relationship between various beef cattle traits and income and expenses of the commercial beef cattle enterprise (Newman et al., 1994).

2. Choice of selection criteria. A subset of the characteristics of animals which can be evaluated or measured, commonly termed traits, will form the basis of the criteria used to estimate the value of breeding animals. Selection criteria may include Breedplan EBV's or other (objective or subjective) measures made on the animal.

3. Development of a pedigree and performance recording scheme. Collection of information on traits in the selection criteria and on pedigrees is necessary for genetic evaluation. Collection of this information requires development of a scheme or system for accurate and reliable identification and measurement.

4. Genetic evaluation. Pedigree and performance data are combined in an analysis to produce EBV's for traits in the selection criterion. Statistical models for analyses of the performance data must be developed and genetic and phenotypic parameters to be used in the analyses must be estimated. Simmental cattle in New Zealand are recorded and evaluated within the Group Breedplan genetic evaluation

5. Use of selected individuals. Decisions need to be made on the animals to mate in the population, this may require identification of elite animals (or herds) and use of genetically superior animals through reproductive technologies such as MOET or AI.

Selection objectives - the crucial first step

To maintain a long-term beef industry future, animals must be produced that will secure a profit for breeders, commercial beef cattle farmers, and processors. Breeding schemes will be required to balance the antagonisms between traits whilst producing a product desirable to the consumer at least-cost. The manner in which this multiple-trait genetic improvement is to be achieved can be described using a selection objective.

The development of balanced and economically based selection objectives is becoming a more common feature of breeding programmes for many livestock species in both New Zealand and around the world. In New Zealand, economically based selection objectives have been developed for dairy cattle (through Livestock Improvement), sheep (customised objectives available for Animalplan users) and swine breeding industries (through the National Pig Breeding Centre). Selection objectives have been developed for beef cattle in New Zealand (Newman et al, 1992), however with one exception, there is little evidence for the use of economically based selection objectives in the New Zealand beef cattle industry. Landcorp Farming, Ltd has used an economic selection objective since 1976 (Nicoll et al, 1979 and Nicoll and Johnson, 1986).

An economically based selection objective essentially contains a list of traits, each of which is weighted by its net financial worth (termed Relative Economic Value, REV). As an example, an REV for carcass weight of steers slaughtered at 18 months may be $0.85. This does not mean that farmers get paid $0.85 for each additional kg of steer carcass weight, rather, this is the net benefit of increasing carcass weight by one kg (compared to a steer for which carcass weight is not increased) minus the costs of producing that extra kg (either through increased feed intake or decreased stocking rate). Similarly, accounting for all sources of farm income and expenses affecting traits, REV's can be obtained for growth, carcass, meat quality, bull and cow fertility, mature cow size and milking and mothering ability.

Genes are transmitted from registered herds (via bull sales) to commercial beef cattle herds. Thus, selection decisions within registered herds will influence performance and profitability of commercial herds at some time in the future. Ideally, a selection objective should contain a list of traits which will be economically important at some time in the future - together with likely pricing signals for that future date. Large shifts in pricing (such as imposition of tariffs) or changes in market requirements (such as a change from frozen manufacturing grade to a chilled product for the table beef market) can affect pricing signals and hence REV's for traits. Decisions about which traits to include in the selection objective should be based on purely economic grounds, and not on whether they are easy to measure or are genetically influenced. The traits in the breeding objective are the ends, not the means to an end.

Through the greater use of information technologies within the beef industry, more rapid and detailed information feedback to farmers and objective measurement of carcass and meat quality, the emphasis placed on carcass and meat quality traits may well change. A few breeders quote the ratio 10:2:1 the relative economic importance of reproduction: growth: carcass developed in the United States more than 20 years ago. However, under Australian conditions, when the aim is genetic improvement of traits (which is the aim for bull-breeders), the balance becomes closer to 2:1:1 (Nicol and Barwick, 1993). The reason for decreased emphasis on reproduction lies with the low heritability inherent in reproduction traits. When breeding is targeted towards meeting the requirements of the high quality end of North Asian markets, Nicoll and Barwick (1993) suggested the ratio may actually appear as 2:1:2

The definition of the selection objective can be envisaged as occurring in four steps:

1. specification of the breeding, production and marketing system
2. identification of sources of income and expenses in commercial beef cattle herds
3. determination of traits affecting farm income and expenses and
4. derivation of economic values for each trait.

All bull-breeders should be aware of factors affecting the profitability of their bull-buying customers, a few breeders routinely record management strategies of their bull-buying customers, enabling them to supply bulls better fitting the requirements of each farmer. Accounting for the requirements of each bull-buying customer would lead to the formidable task of developing as many separate selection objectives as there are bull-buyers. To simplify this task, the role of the breed within the beef industry should be considered, from a recent survey of New Zealand Simmental breeders, the majority of bulls (90%) were sold to beef cattle farmers with the majority of female progeny of these bulls (70%) being slaughtered, as opposed to being retained for breeding. Terminal sire use of Simmental bulls within the beef cattle industry necessitates the development of selection objectives focused on growth rate, carcass and meat quality traits with less emphasis placed on maternal and reproductive traits.

In the development of selection objectives for different cattle types in the US, MacNeil et al (1994) derived selection objectives for specialist terminal sire and maternal lines of cattle within a large breeding scheme. For a purely terminal sire breed, (no female progeny retained for breeding on commercial beef cattle farms) the relative selection emphasis for efficiency of liveweight gain (kg live weight gain / kg feed eaten), male fertility, dressing out percentage, weaning weight (direct) carcass grade and lean meat yield all increased compared to selection of specialist maternal line cattle. Discussions with Simmental breeders however indicate that the breed should be utilised in both a terminal sire and maternal capacity. REV's derived for traits will depend on how Simmentals are used within the breeding system. Several different selection objectives for Simmentals could be developed, each one differing slightly depending upon bull use within commercial beef cattle herds and changes in farm production and financial circumstances.

The flow of genes through a breeding industry affects REV's assigned to traits. In the case of a terminal sire breed where all progeny are slaughtered, the flow of genes is simply from registered to commercial herds. For a maternal breed, the genes from registered herds are transferred through commercial beef cattle herds over a number of generations (since a proportion of female progeny are retained in each generation). REV's derived for traits should reflect the frequency with which traits are expressed in addition to frequency of expression in latter generations. The value of traits expressed at some time in the future is less than for traits expressed earlier (due to inflation and risk), thus their value will have to be discounted. The method of discounted gene flow is often used to account for differential expression of traits within a year and throughout subsequent generations.

Through the established use of Group Breedplan the Simmental breed in New Zealand is well placed to consider options for the development of multiple trait selection objectives. The efficacy of such technologies will be greatest if they are adopted within herds having the largest genetic impact on the Simmental beef cattle breeding industry. An analysis of 1994 born Simmental calves reveals that 13%, 56% and 22% of calves born, sires of calves born and dams of calves born were themselves sired by overseas bulls, suggesting that some of the herds having the largest impact on the Simmental breed in New Zealand are located offshore. Excluding overseas herds from this analysis, nearly all calves born are sired by bulls arising from 40 herds.

The implementation of multiple trait selection objectives in Australia is facilitated through the development of BREEDOBJECT - a software package enabling breeders to cutomise breeding objectives for their bull-buying customers. Financial and physical farm information from bull-buying customers are entered into the programme and based on an appropriate time horizon for improvement of traits, REV's for traits are derived. Also included in the package is the development of customised selection indices enabling the weighting of Group Breedplan reported traits. It is worth re-emphasising however that selecting on traits using Group Breedplan EBV's is a means to an end not an end in itself. Increasing profitability of the bull-breeder, bull-buying customers and other industry participants remains the aim of selection.

Acknowledgments:

Thanks to Dr. Mark Enns, Landcorp Genetics Unit for his helpful comments and suggestions for this article.

References

Newman, S.; Morris, C.A.; Baker, R.L.; Nicoll, G.B. 1992. Genetic improvement of beef cattle in New Zealand: Breeding objectives. Livestock Production Science: 32: 111-130

Newman, S.; MacNeil, M.; Golden, B.; Barwick, S. 1994. Implementation and use of selection indexes in genetic evaluation schemes for beef cattle. Proceedings of the 4th genetic prediction workshop, Beef Improvement Federation, Kansas City.

Nicol, D.C.; Barwick, S.A. 1993. Breedplan EXPO notes, p39.

Nicoll, G.B.; Gibson, A.E.; Dalton, D.C. 1979. The recording and data-handling procedures used in the Angus Cattle Breeding Programme of the Rotorua Land Development District of the Department of Lands and Survey, Wellington.

Nicoll, G.B.; Johnson, D.L. 1986. Evidence of genetic improvement in the Angus Breeding Programme of the Department of Lands and Survey. Proceedings of the New Zealand Society of Animal Production, 46: 67.

Ponzoni, R.W. 1989. Accounting for both income and expense in the development of breeding objectives. Proceedings of the 9th Conference of the Australian Association of Animal Breeding and Genetics: 55-66.