Last update: March 30, 2012 02:29:53 PM E-mail Print

 

Principles of Group Breeding

 

C. V. Pettit. S.A. Fleece Testing Centre

Grootfontein P.B. X529

Middelburg Cape. 5900

 

ORIGIN OF THE CONCEPT

The concept of group breeding originated independently in New Zealand and Australia at about the same time in 1967. It is interesting to note that the founders of the first groups, "The Australian Merino Society" and the "New Zealand Romney Development Group", became acutely aware of the limitations of the traditional system of breeding through the extensive use of flock recording and measured performance of individual animals in their own stud flocks.

From these records it became clear that, not only was the incidence of females with really outstanding performance too low for any meaningful progress to be made, but that individual animals were emerging in daughter studs with performances equal to the best in the parent stud. From these observations, the idea of co-operating with other breeders in order to identify and regroup the top producers into more effective sire breeding units was conceived.

The term "group breeding" is no longer new to the South African breeding scene. Since the introduction of the concept to this country in 1971 it has received considerable publicity and, although adoption of the idea, like all new ideas, was initially on a limited scale, it has gained increasing credence especially in the commercial breeding sector. Because the concept is more acceptable to commercial breeders with small to average size flocks or herds, it is logical that it has found its greatest application in this sector and in a group context. This does not, however, preclude individual breeders, either in the stud or commercial sector from exploiting the advantages of this breeding system, provided that their scale of operation can be sufficiently enlarged.

At the present time there are 11 Merino and 5 dual-purpose sheep groups, 1 Angora goat and 3 beef cattle groups in South Africa. Included in the dual-purpose sheep groups are 3 Dohne Merino groups comprising registered sheep.

 

COMPARISON OF BREED STRUCTURES

Although both systems follow the same stratified pyramid structure, a comparison of the "Traditional" and the "Group Breeding" systems, as depicted in the two triangles in Figures 1 and 2, clearly illustrates the essential differences.

 

 

The triangle in Fig. 1 shows the typical breed structure, which has been practised by livestock breeders throughout the world for many generations. The registered studs in the top strata of this system comprise mainly so-called "parent" and "daughter" or "multiplier" studs, the latter supplying the majority of the sires for the commercial sector. A small proportion of these studs follow a closed breeding system with no introduction of genetic material from an outside source. By far the greatest proportion practices an open breeding system with a free exchange of sires between breeders. The limited size of many of the breeding units necessitates the periodic introduction of sires from other sources to offset inbreeding degeneration.

Any genetic change, which may be effected in the registered studs, is transferred to the commercial flocks or herds, mostly by rams or bulls used in natural service.

Since there is little if any return-flow of genetic material from the commercial to the stud sector, this large commercial population has no genetic influence on the registered studs and is precluded from making any contribution solely as a result of the registration barrier based on pedigree. Not only does this tend to limit the effective size of the stud breeding units, but the presence of genetically superior females in the large base populations is ignored as a potential source for generating sires of high breeding merit.

The integrated or group breeding system depicted in Fig. 2 shows the two-way movement of males and females between the nucleus or sire breeding unit and the satellite or contributing flocks or herds.

In contrast to the traditional system, this is an "open" system of breeding in which large foundation populations become an integral part of the whole breeding system by still contributing a proportion of the female replacements of the nucleus or sire breeding units after the initial establishment phase has been reached.

 

KEY FEATURES

The most important feature of an integrated breeding scheme is the direct advantage obtained by screening large populations of animals for the highest producers. In this way sire breeding units can be established with a high standard of production at the outset, which would take many years to attain by selective breeding in smaller units of average production. As shown by Hight and Rae (1970), if approximately 20 times the number of ewes required in the nucleus are screened, these advantages can be considerable, In the Romney sheep this gain could, for example, exceed the average of the contributing flocks by as much as 12,3 kg weight of lamb weaned, 1, 14 kg of wool, lambs 8,6 kg heavier at weaning and ewes rearing 90% more Iambs to weaning if only one character is considered. The size of the selection differentials, which can be achieved, will of course depend on the size of the population screened so that the gains quoted are by no means the limits which can be achieved. The creation of large populations by the integration of foundation populations in the breeding system is directly in line with the modern concept of population genetics with its statistical approach to breed improvement, where the shifting of the population average is the objective rather than the quest for the ideal individual.

A second important advantage embodied in the concept is that, when once the nucleus has reached capacity in 4 to 5 years, the foundation flocks are still screened annually for elite females which are transferred to the nucleus to form about half of its annual replacement requirements. The on-going introduction of genetic material from the satellite flocks increases the effective size of the nucleus, ensures high selection intensities and shorter generation intervals, two essential elements to more rapid selection response which have hitherto not been exploited in the traditional breeding system. The constitution of most groups provides for the recycling of surplus females, often with outstanding performance but with minor faults, to the contributors, thus preventing the loss of valuable genes from the group. All the foregoing features lead to greater genetic diversity and reduce the possibility of any early selection limit being reached.

 

ESTABLISHING A GROUP BREEDING SCHEME

The initiation and successful operation of a group-breeding scheme is dependent on a number of important considerations which are not always easily met, and for this reason the formation of large numbers of group breeding schemes is unlikely.

 

TWO AND THREE TIER BREEDING SYSTEM

Group breeding schemes may operate either as a two or three tier system. The two-tier system is, however, more commonly adopted, especially during the establishment phase, because of its simplicity and ease of operation. The two-tier system shown in Fig. 3 consists of the nucleus flock and its manager, usually chosen from the group members, and the contributing flocks owned by the remaining members.

 

 

The three tier system, on the other hand, is simply an extension of the two tier system in which existing group members widen their field of operation by screening other flocks to form their own nucleus, which in turn supplies the newly formed third tier with Its sire requirements. This is an effective way of increasing the number of animals as well as the number of members of a group. The addition of a third tier could quite easily result in a tenfold increase in the number of animals in a group. Although this widening of the gene pool would have some genetic advantage during the establishment phase, there is a distinct danger that the scale of operating may reach the level where this advantage may be partially or wholly negated by a decrease in the organisational and operational efficiency in the group.

 

OPTIMAL GROUP STRUCTURE

The optimal structure for group-breeding schemes has been widely researched notably by Turner and Jackson (1972) and more recently by Rae (1974). Naturally the optimal structure will vary to some extent depending on certain flock statistics such as lambing percentage, survival rate from birth to breeding age, ratio of males to females, etc. The following structure has been suggested as a working guide but could be adapted to suit individual requirements:

(1) The optimum size of the nucleus flock in relation to the pool (total females mated annually by all group members) appears to be about 1:20 but this is not regarded as critical. It has also been suggested that the nucleus could be between 5 and 10% of the pool size.

The optimum number of breeding animals in a group appears to be about 20 000 in the case of sheep.

 

(2) The initial intake of females screened from members' flocks should be between 5 and 10% of the maiden ewes and should be the same for all flocks, since the genetic status of individual flocks is unknown. If performance records of the ewe flock or cowherd are available, the selection may be extended to include mature animals as well. It is considered preferable to adopt the higher level of intake during the establishment phase, in order to build up numbers in the nucleus flock as quickly as possible. This allows for rigorous culling of ewes with poor performance after transfer to the nucleus.

With a 90% fertility (lambs born/ ewes mated) and a 3% mortality from birth to the 2-tooth selection age in the nucleus flock, members' contributions will have to be reduced to ± 2,5% of the maiden ewes in order to maintain the correct replacement ratio in the nucleus after it has reached capacity.

 

(3) The optimum number of age groups in both the nucleus and contributing flocks is closely related to fertility. The suggested number of age groups when fertility is in the region of 100% is as follows:

(a) In the nucleus flock: Three age groups of ewes and two age groups of rams.

(b) In the contributing flocks: Four age groups of ewes and three age groups of rams.

 

(4) Ewe replacements in the nucleus flock should be made on the basis of 50% from nucleus progeny and 50% from the contributing flocks. Assuming the aforementioned age structure, fertility and mortality, only about 40% of the female progeny born in the nucleus will be required to meet the 50% replacement level.

 

(5) Since the exchange of male and female animals between the nucleus and contributing flocks is a permanent feature of group breeding, some equitable form of compensation must be arranged between the parties concerned. The simplest and most commonly adopted system is to exchange males for females at a predetermined but flexible ratio e.g. 4 ewes: 1 ram.

 

The aims of a group are non-profitmaking and the exchange ratio should be adjusted in such a way that it will be equitable to both the nucleus manager as well as the contributing flock or herd owners.

 

OWNERSHIP OF STOCK

Since integrated breeding schemes involve more than one person, ownership of animals becomes an important consideration.

Group breeding schemes established from commercial animals with relatively lower monetary value than stud stock usually adopt the exchange system since it is a simple and equitable form of compensation.

The outright purchase of stock by both group members and the nucleus owner is usually preferred by groups comprising registered animals.

A third alternative is for a group to form a company or incorporated society, profits being distributed amongst the group members.

The fact that the contributors in an integrated breeding scheme supply the greater portion, if not all the foundation stock for the nucleus and continue partially to maintain it after stabilisation, makes it imperative that their stakes in the venture are protected against the loss of this valuable breeding material through events such as the death or insolvency of the nucleus manager. The members of groups in the Republic have covered themselves against such an eventuality by leasing a predetermined number of breeding stock to the nucleus manager.

 

FAMILY IDENTIFICATION

The additional trouble of identifying and maintaining each member's contributed ewes and their progeny as separate families in the nucleus is considered well worthwhile. In this way it is possible for members to select their ram requirements from their own families, thereby ensuring absolute fairness and providing a guarantee that only the best breeding material reaches the nucleus at all times.

 

FURTHER ADVANTAGES OF GROUP BREEDING

Apart from the more effective manipulation of breeding principles, there are a number of other features which could lead to greater overall efficiency of a cooperative breeding system.

This is undoubtedly one of the biggest obstacles encountered by small breeding units in the traditional system.

Ewe contributions to the nucleus from members' flocks are also bred in the same environment and comparison and selection of their female progeny for replacement purposes is therefore also more precise.

 

 

APPLICATION IN THE LIVESTOCK INDUSTRY

The fact that the integrated breeding concept has been more widely adopted by commercial breeders may have created the impression that the concept is less suited for application in the stud sector. Whilst it is conceded that there are more complicating factors such as the large capital investments and the position of individual breeders in the hierarchy which make the principles of the concept less attractive to stud breeders, many of these difficulties could be overcome. Technically speaking, application of the integrated breeding system by the stud sector could have the most profound effect on the livestock industry since they already have the organisation and machinery to pass genetic improvement on to the commercial sector most effectively.

In the light of the apparent stagnation in wool production, application of these principles in conjunction with the effective use of performance testing could quite conceivably provide the wool industry with the shot in the arm which would lift it out of the doldrums. Although there is no doubt numerous ways in which an innovative group of stud breeders could apply the group-breeding concept, the two most obvious are the following:

 

(1) STUD BREEDER - CLIENT CO-OPERATION

Apart from the not insurmountable problem of accepting unregistered flock into the stud from clients' flocks, this is the simplest and most acceptable way for stud breeders to initiate group-breeding schemes. Without actually increasing the number of animals in the stud, breeders could, by annually screening high performance females from clients' flocks, raise the standard of the stud flock and at the same time increase the effective size of the unit, thereby decreasing their dependence on sires from outside sources.

 

(2) CO-OPERATION BETWEEN STUD BREEDERS

A group of stud breeders with similar breeding objectives could establish a nucleus of the most outstanding females screened from their own stud flocks which would be capable of supplying high performance sires required as replacements in their own stud stocks. In this way they would retain their individuality and at the same time overcome two of the major problems m the traditional stud breeding system, viz: the limited size of many of the studs and the associated problem of inbreeding degeneration and the uncertainty and high cost involved when replacing sires of unknown breeding value from outside sources.

The nucleus could be run as a separate stud on the property of one of the group members or alternatively the group could form a syndicate to acquire a separate property on which to run the nucleus flock.

In the same way as group breeding schemes screen contributing flocks for elite females, individual commercial breeders with large flocks could establish a nucleus of high performance ewes for the purpose of breeding their own sire requirements. Breeders with large ewe flocks could also increase the effective size of stud breeding units by the integration of their studs and flocks in an open nucleus system. In the case lated that the stud breeders could make approximately two and a half times more progress by incorporating their large commercial flocks in their breeding enterprise.

 

SUMMARY

Although it cannot be denied that group breeding is associated with certain specific problems such as the risk of spreading disease and organisational difficulties, which tend to increase in relation to the scale of operation, it has been shown that most of the problems can be effectively controlled by strict adherence to a carefully drawn up constitution.

The condemnation of group breeding on the inferior outward appearance of animals in some groups is totally unfounded since the managerial level and selection techniques which are largely responsible for an animal's phenotype are entirely divorced from the principles of this or any other system of breeding.

That it is a viable system of breeding is adequately borne out by the growing number of groups in New Zealand, Australia and the Republic. Although genetic improvement is difficult to monitor in commercial ventures, there is reliable evidence of the effective employment of this breeding system in raising a number of production traits of the large Romney flock in the New Zealand Department of Lands and Survey Breeding Scheme at Waihora (Hight 1975).

 

REFERENCES

ERASMUS, G.J., 1977. Die Teeltstruktuur van die Suid-Afrikaanse Merino. M.Sc.Agric. treatise Univ. of the O.F.S.

HIGHT, G.K. & RAE, A.L., 1970. Large-scale sheep breeding: its development and possibilities. Reprinted from Sheepfarming Annual 1970. M.Z. Dept, of Agric. Ruakura Agricultural Research Centre, Hamilton, New Zealand. Public  No. 532.

HIGHT, G.K., 1975. Lands & Survey Romney Breeding Scheme. Annual Report 1974-75. Whatawhata Hill Country Research Station. (Unpublished).

JACKSON. N. & TURNER. H.N., 1972. Optimal structure for a co-operative nucleus breeding system. Proc. Ausl. Soc. Anim. Prod.. 9. 55-64 (Quoted by Rae. 1974: paper presented to the first conference of the New Zealand Federation of Livestock Breeding Groups. Executive Officer. P.O. Box 11137. Wellington. N.Z.)

RAE. A.L., 1974. The development of group breeding schemes: some theoretical aspects. Paper presented at the first conference of the New Zealand Federation of Livestock Breeding Groups. Executive Officer. P.O. Box 11.137. Wellington. N.Z.

 

Published

Karoo Agric 2 (3), 11-16