Selection of Cashmere Sires
One of the most critical decisions that a buck breeder or commercial breeder has to make is the selection of sires. The rate of genetic improvement within any flock largely depends on the genetic superiority of the sires used. It is critical that the assessment of bucks is carried out in a systematic manner and standards are maintained to ensure positive genetic gain.
Most breeders carry out a series of cullings as bucks mature, which take into account objective measurement of fleece and body characteristics and visual appraisal. It is most important that breeders clearly identify their own breeding goals as progress will be made more difficult if these goals are changed from year to year.
For example, breeding goals for cashmere producers are usually centred on fleece value and live weight. Ignoring colour for the moment, the value of cashmere is largely determined by fineness and down weight. Unfortunately, it is difficult to make a major reduction in fibre diameter without a drop in down weight and live weight, or to increase down weight or live weight without an increase in fibre diameter. This caused quite a dilemma for early breeders in choosing breeding goals.
Fortunately, a research program on the Australian cashmere goat was undertaken at Wollongbar Agricultural Institute, between 1979 and 1992. (Refer to Goat Note " Breeding Cashmere in Australian Goats"). Amongst many things, this program produced indices to assist the breeder with this problem. However, the breeder was still left with the decision of whether to concentrate on fineness or down weight first as these traits cannot be improved simultaneously.
The selection of potential sires starts at the joining of their own sires and dams. The progeny of superior does and bucks are more likely to produce superior offspring themselves, but line breeding should be avoided. This compels breeders to source and breed superior bucks from a number of different blood lines.
Most breeders are reluctant to keep the superior male offspring of inferior parents because of the possibility that much of their superior phenotype may be due to environmental factors. For similar reasons, it is important that young bucks from a drop are reared under the same conditions. This includes such factors such as feed availability, through their dam’s milk and the pasture, shelter and time of year they were born. Progeny of twin and multiple births should be assessed with this in mind if a high level of reproduction is a breeding objective. The first culling will usually be carried out at marking, at around eight weeks of age. Those showing obvious conformational defects are culled such as cow hocks, under or over shot jaws, cryptorchids (one testicle descended), and those bucks that have done poorly or are lightly boned.
Many breeders will choose to cut all coloured animals at this stage. The decision to keep any coloured bucks is a personal choice - bearing in mind that severe price penalties exist for cashmere bearing coloured fibres. Some breeders also cull for characteristics such as a split purse although it has not been shown to have any relationship with reduced fertility.
A second culling may be carried out at weaning. Some breeders elect to maintain a set percentage of the drop at this stage while others follow no hard and fast rules. Most of the weaner bucks will probably be kept until their first shearing.
Thereafter, the animals are shorn, fleeces weighed and objective measurement statistics obtained on the fleece production. Breeders need to have a grasp of the level of performance that can be expected and have a set of criteria to be met, so that those below this level are culled. At ten to twelve months, the best young bucks may cut from 150 grams of down at 13.5 to 14.5 microns ranging to well over 200 grams at 16.0 microns.
Monitoring bodyweight in a dual purpose breeding programme is very important due to the negative genetic correlation between bodyweight and down production, which will tend to lead to smaller, high producing animals.
Other conformational faults may become apparent by 12 months such as poorly formed pasterns or feet. Some people may also consider culling an animal which exhibits a low tolerance to parasite burdens. The cut-off criteria for fleece performance will depend largely on personal selection criteria. This question may be approached from two different angles. Some breeders keep a top percentage of the drop, which have been produced from a nucleus flock of superior breeding does. Others may elect to keep the male progeny from superior parents, which meet a certain level of performance.
In the end, the retained bucks should combine good body weight, size, and conformation for meat production with the required commercial down weight, micron, yield and length characteristics. The down coverage should be dense and extend onto the buck’s neck, throat, belly, britch and scrotum. A good temperament and sign of libido are desirable.
The Wollongbar research showed that, on average, cashmere animals coarsen by 1.25 micron between the first and second fleeces, and by 0.5 micron thereafter. A second full fleece test at two years will confirm these changes. As a guide, down production can be expected to double between 12 months and maturity with an associated increase in fibre diameter.
Progeny evaluation is generally used in two ways:
Selecting Breeders vs Culls
The aim in this case is to rank groups of animals raised under identical conditions from best to worst, with respect to breeding aims and in accordance with the known heritabilities of the desired traits. In the case of cashmeres, these traits would normally be fineness and down weight, without prejudice to liveweight or fertility. The best way would be to use the heritability based selection indices and procedures given in Goat Note "Breeding Cashmere in Australian Goats". Note that care must be taken when test results are received to ensure that there are no significant test errors, before the final calculations are made.
Although not stated in the Goat Note, these techniques can be used to rank does, but the number of calculations involved when the group size is large would probably dictate that a specially progammed computer be used. Fortunately, the individual calculations are reasonably simple and it is not difficult to programme the personal computer to do this work, using common software.
Alternatively, the NSW Department of Agriculture has provided a less accurate, but simpler, selection method for increasing down weight whilst holding liveweight and micron constant. This is shown here in a slightly modified form. You can proportion the figures to your own situation, but note that this method is less reliable the smaller the numbers used. The method is to:
The estimated increase in DL per animal of the next generation is 8.6gm.
Note that there are no indices to select for fleece colour. Colour is determined by visual assessment. White is dominant, black is recessive, and ginger is very persistant. Culling is solely based on pre-determined breeding aims.
Comparing Sires against Breeding Aims
For sire comparison it is vital that the groups of does to be joined to each sire are randomly selected, and there should be at least 30 does per group for reasonable reliability of results.
The progeny of each group are then individually measured for each of the characteristics that you wish to consider. For cashmeres, these would normally be live- weight, down length, total down weight and micron.
The group averages for each characteristic are obtained, and these averages are compared for
each sire, to see which sire provides the greatest improvement for each characteristic. Decisions, based on breeding aims, can then be made on which sires to use next time.
In addition, the group averages of the progeny provide an indication of how the herd is developing. Whereas, individual animal performances are not as objectively informative.
Purchase of bucks
From time to time, many growers will consider introducing bucks from other flocks to fulfil a purpose within their own herd. The introduction of other animals may be useful to increase genetic variation, especially where the effective population size is small. A buck from an outside source may not have a higher down weight than one’s own bucks, but may have better coverage, lower diameter, well defined down and guard hair or superior size and frame. However, the assessment of such animals can be difficult when the effects of different environments on an animal’s performance are not known. Thus, the more information the breeder can provide, the easier it is for the purchaser to make decisions.
Ideally, objective fleece tests of micron and yield for more than one fleece should be available for each buck offered for sale. As a minimum, at least one fleece test for either the first or second fleece should be available, and remember most animals coarsen with age.
In addition, evidence that the vendor keeps comprehensive herd records, with the opportunity to view those records pertaining to the sale animals and, better still, those of their progeny, can provide a higher level of confidence.
Certificates of success in the ACGA National Fleece Competition are helpful, but do not forget the bands of error associated with individual fleece tests. Show results are better than nothing, but bear in mind that the competition at some shows is not always high.
Should little or none of this information be available, one could be forgiven for not going to the final step, which is visual appraisal of potential purchases. At this stage one would look for visual evidence of the claimed characteristics, and include size for age, feet and general confirmation.
© 2000 ACGA