- Performance Testing of Angora goats - a critical review
|Last update: March 23, 2012 10:42:59 AM|
Performance Testing of Angora goats - a critical review
G J Delport
S.A. Fleece Testing Centre ADSRI
Grootfontein College of Agriculture
Private Bag X529
The world-wide success of performance recording schemes led to the general recognition that these schemes constitute the basis of breed improvement of virtually all kinds of livestock in developed countries. The concept of performance recording however gave rise to many conflicting views as to its exact aim and meaning between breeders on the one hand and animal scientists on the other. The general definition for performance recording is the accurate measurement of all important traits and the subsequent transformation of these data into useful information for the individual breeder. Therefore, performance recording is not a breeding system and should not be confused with the formulation of breeding policy which is the explicit task of the individual breeder and also of breed societies.
The implementation and development of performance recording in the Angora goat industry will be discussed against the back-ground of the world-wide operation of recording schemes for other types of livestock.
Historical review of performance recording
Performance recording is no new concept. Nel (1974) mentioned that Daubenton measured the fineness of wool with a micronmeter as far back as 1779. Fleece weights of fine woolled sheep were also recorded in New England more than a century ago. Official performance recording schemes were however founded only at the turn of the century. The oldest recording scheme namely the "Vejen" milk recording scheme was established in 1895 in Denmark. Other countries such as Germany, Sweden, Norway and Finland, which still have the most sophisticated schemes, followed soon. The South African milk recording scheme started in 1917 (Erasmus, 1974).
The success achieved by these schemes, although difficult to analyse accurately, proved to be fundamental in increasing the level of production of animal products as well as the efficiency of production.
Ahmed (1984) mentioned an average first lactation milk yield of 5 066 kg milk for high producing herds in Britain. According to Hickman (1984) the milk yield for first calf heifers for different breed groups in Norwegian gene sampling tests varied between 5 502 and 5 734 kg milk. In contrast Van der Merwe (1986) reported an average milk production for the South African national herd of only 2 100 kg. The average production for performance tested herds, although relatively low in comparison with the USA and the European countries, was 4500 kg. Van der Merwe (1986) also stated that the growth rate of Shorthorn herds participating in the Beef Cattle Performance and Progeny Testing Scheme increased by 32% and the feed conversion efficiency by 13% over the past 15 years. Participation in the South African performance recording schemes increased dramatically over the last decade on account of the results achieved by members of the schemes as well as the increased efficiency of extension work and technical soundness of the official schemes. Henderson (1986) mentioned that the number of masses recorded for phase A of the beef cattle scheme increased from 127 000 in 1975 to 284 000 in 1985. The mutton sheep and goat performance testing scheme also experienced an increase in the number of participants from 124 in 1981 to 578 in 1985. These facts clearly indicate that breed improvement goes hand-in-hand with participation in official recording schemes.
It is an extremely difficult task to measure genetic change that has taken place as the result of performance recording or otherwise "hand and eye" selection. The reason is that certain sociological effects as well as the effects of environmental and management changes are confused with genetic effects. It is therefore necessary to separate genetic effects from all other effects in such analyses. Berger, Wilson & Wilham (1984) used Henderson's Mixed Model Methodology to analyse the performance data of the American Angus Association in this manner. The results shown in Fig. 1 indicate that weaning weights changed genetically at a rate of 2,2 Ib per year as the result of effective recording practices followed by members of the society. The possibility of this rate of genetic progress should be encouraging for any breeder intending to make use of performance recording.
Implementation of performance recording in the mohair industry
It is well known that the Angora goat industry developed from extreme poverty and near extinction to the most profitable small stock industry in South Africa. This is confirmed by the comparative gross margins of R50,00 for Angoras, R21,50 for mutton sheep and R17,50 for fine woolled sheep published by Thompson (1985). This development had a profound effect on the mohair industry as well as the implementation of a recording scheme.
The first direct consequence of the rapid increase in mohair from 108,7c per kg in 1970 to 1554,3c per kg in 1984 was an increase in the number of Angora goats. According to the official figures of the Mohair Board, the numbers increased by approximately 58% from 1,2 million in 1970 to 1,9 million in 1984. Although expansion of the stud industry lagged behind, the number of studs increased from 60 in 1970 to 114 in 1986. The effect of this horizontal expansion was that commercial Angora goat farming has outgrown the stud industry. Consequently so-called "pirate breeders" started to breed rams from commercial stock and selling them to other producers. This over-demand for rams means that the possibility for accurate selection is severely impaired since the numerous novices in the industry are willing to pay relatively high prices for inferior breeding stock. This situation is hardly suitable for any performance recording scheme to take its course.
The second consequence of relatively high product prices is a change in the nature of farming practices. Although Angoras were traditionally kept under extensive grazing conditions, even zero grazing systems became profitable. Provision of artificial shelter, increased supplementary feeding and hormone therapy are rapidly becoming standard farming practices (Erasmus, 1986). 'These practices may have adverse effects on especially adaptability and fertility of the animals and should be considered in the formulation of breeding goals and! or choice of traits for a performance recording scheme.
The profitable commercial industry is fundamental in the economic prosperity of the stud industry. The average price of R2 776,28 realized for I 224 rams sold on sales under the auspices of the Angora Goat Stud Breeders' Society during the 1985/86 season reflects the economically favourable implications for the individual stud breeder. It is clear that the exchange of potential stud sires takes place at an extremely high monetary value. This situation favours the traditional method of stud breeding by which the breed society concentrates on maintaining:
- Breed identity
- Purity of breeding (pedigree registration)
- Breed standard
Although the first may be justified, the second and third may represent stumbling blocks in the way of breed improvement.
Registration of animals in a herd book on the basis of accurate breeding values obtained by combining measured performance and certain subjectively scored important traits with pedigree information can be regarded as a worthwhile aim for any breed society. Barton (1984) however mentioned that registration with an animal's pedigree as the sole criterion does nothing to improve the merit of a breed. The recent step taken by the Angora Goat Stud Breeders' Society to close the herd book is therefore questionable since it will inevitably prevent new genetic material from entering into the pedigree segment of the breed.
In practice breed societies often combine a written "standard of excellence" together with pedigree information to form the basis of registration. According to Barton (1984) the wording of these descriptions is often colloquial, imprecise, and difficult to understand by the novice and may emphasize features of the animal that are in conflict with commercial realities. Several examples exist where the breeding goals and selection policy set by traditional breed societies diverged to such an extent from those of the commercial sector, that new societies were formed on the basis of the requirements of the commercial farmer. In South Africa the prime example is that of the Merino industry. In this case the now well-known performance register for Merino sheep evolved from the sector of commercial producers with the goal of breeding animals well adapted to conditions of natural grazing. The basis of this register's (formerly a separate society) breeding policy was participation in the National Woolled Sheep Performance and Progeny Testing Scheme in order to select accurately for economically important production characteristics. Simultaneously with this development commercial Merino breeders formed various group breeding schemes with the same ultimate aim of breeding animals superior in productive performance and more adapted to natural veld conditions.
The Angora Goat Breeders' Society should take note of the above-mentioned sequence of events in order to prevent such uncontrolled developments taking place in the mohair industry especially in view of letters by commercial mohair producers in the popular press. In order to deal with the situation, the breed society should adopt the following approach, in the words of Barton (1984): "An integrated and well controlled approach to animal improvement must be instituted and adhered to by the executive of the Breed Society. In this regard a working relationship with animal scientists is essential.
The implementation of performance testing in especially the Angora goat stud industry is heavily dependent on efficient extension work to make individual breeders aware of the bearing of the current economic situation and the traditional stud breeding strategy on future breed improvement. Demonstration of the principles of population genetics and specifically the utilization of the precious natural resource of variation between animals by accurate measurement to shift the average production levels in the population, should be fundamental in this regard.
Performance recording programme
On account of the need for a more scientific approach towards breed improvement and also partly after observing the successful operation and degree of sophistication of performance recording for other livestock species, the mohair industry approached the Department of Agriculture in 1979 with the request to assist in the conduct of a feasibility study to investigate the possibility of starting a performance recording scheme for Angora goats. Consequently a concept scheme was drawn up by a committee consisting of representatives of the Department of Agriculture, the Mohair Growers' Association and the Angora Goat Stud Breeders' Society.
During the planning stages it was decided to utilize the unique breed structure of the Angora (Table 1) to ensure effective dissemination of possible breed improvement throughout the entire industry. Individual attention is currently devoted to the on-farm aspects of the recording scheme in the top tier studs. All stud breeders are however encouraged to participate in the scheme.
Information on phenotypic and genetic parameters of important traits is, to say the least, incomplete. It was therefore decided on the initial implementation of a pilot scheme. One of the main functions thereof should be the collection of information needed to formulate breeding plans.
After approval of the concept scheme by the AGM of the Stud Breeders' Society in 1982 the pilot scheme was launched in 1983. Owing to the above-mentioned lack of information it was decided to implement the scheme in different stages, of which the first two are currently operational.
Outputs of the scheme include:
- Corrected weaning weights of kids giving their percentage deviation from the contemporary group mean. Although this output serves as a basis for preliminary culling, its main purpose is to serve as a checklist for the data used to calculate a dam summary. First results for this phase (Delport, 1984) indicate a weaning percentage of 89,3% and a growth rate for ram lambs of 120 g per day. These figures indicate high levels of nutrition and management efficiency in studs. It is however doubtful whether selection under these conditions will prove to be effective in the event of more extensive farming conditions becoming a reality in future.
- Performance at second shearing giving the percentage deviation in fleece mass, body mass and fibre diameter. The animals are also ranked according to a selection index of the breeder's choice. This stage was implemented on the basis of repeatabilities and correlations calculated on data of the Department of Agriculture and Water Supply's experimental flock at the Jansenville experimental farm (Delport, unpublished). This study indicated a high correlation of production at second shearing with lifetime production. It also confirmed the findings of Shelton (1984) that the high positive phenotypic correlation of fibre diameter with body mass as well as with fleece mass may limit genetic progress in these characteristics. The only solution to this problem seems to be the objective measurement of these traits so that they can be quantified and combined in selection index selection to ensure the maximum rate of genetic progress no matter how little it may be. Other preliminary studies on practical aspects, indicate that the inclusion of bellies into fleece weight measurement is possibly justified and that the variation in fibre diameter over the goat's body is far less than expected. Therefore the taking of mid-rib samples for fibre diameter determination is possibly correct. Further verification of these aspects is however needed and research is still underway.
- Subjective evaluation of all traits necessary for registration on the basis of linear scoring. The aim with this phase is to investigate aspects of functional efficiency and to monitor any possible correlated responses to selection on measured performance (Delport & Erasmus, 1984).
- Dam summary based on the use of reproductive performance and total weight of kids weaned to improve the maternal ability of ewes. This output will be updated annually.
- Sire summary based on breeding values for all objectively and subjectively assessed characteristics will be updated every year.
Currently the possibility of using mixed model methodology to determine both maternal breeding values as well as expected progeny differences on an across-herd basis is being investigated. This type of analysis will make it possible to compare the breeding performance of an animal born in one stud with that of another animal born in another stud. One will also be able to predict the breeding value of young male animals even before they produce any progeny. Pedigree information is however fundamental in this type of analysis and breeders are urged to identify both parents of all progeny born is accurately as possible. This exciting new prospect may be of tremendous value to members of the scheme, in order to identify superior genetic material.
Imperfect as the Angora goat scheme may as yet be, it can be regarded as an important development to increase the rate of genetic progress in the mohair industry. The collection of reliable information on which to base the definition of breeding aims and implementation of a scientific breeding programme, as well as an effective extension service amongst breeders, seems to be the priority in the development of the scheme. Some problem areas regarding the nature of the industry have been identified in this article and it is hoped that breeders will contribute in a positive way to solve these problems.
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