Blood Counts

Part II - Breeding and Genetics: Selection

Most alpaca breeders gazing upon their herd, will hope one day to see before them a vision of healthy, beautiful and productive alpacas. Each breeder will probably have a different view of what this means to them. It depends on your goals and philosophy. Your reasons for breeding might, for example, be to produce show ring winners, or to refine temperament, conformation, colour or fibre characteristics. A properly constructed breeding programme will place different emphasis on these different properties. Matings that are accomplished purely because of the convenience of available males and females are likely to be less productive in achieving your goals.

In the first part of this series, we took a short look at the concepts of genetics. In this second part we will take a look at the concepts of selection as tools to assist us in achieving our ideals.

Selection is the process used by breeders to control which alpacas will become parents, and in which combination. How long they will be useful and how many offspring they will produce. Selection is therefore a force for change in the overall makeup of a herd. In the hands of humans it is a powerful. and therefore somewhat dangerous tool in that its results are irreversible in the short term. Mother Nature's selection is by the survival of the fittest. In a single decade for example fleeces presented to markets in Arequipa changed from 70% coloured to 70% white as a result of only allowing white males to be sires.

The aim of selection is to make the next generation better than their parents. This is not simple. We must select for traits which are heritable, and that can be measured so improvements are recognised. Since the environment plays a significant role in determining the phenotype, effective selection must be based an alpaca's ability to transfer the desired traits genetically.

Selection can involve any trait that is heritable, be it size, fibre colour, density or fineness or conformational aspects. As breeders we need to establish our own programme based on our goals. One philosophy followed by show participants is the production of excellent individual animals. This approach will tolerate a fair degree of variation as long as some excellence is produced. They will be selected from the rest and used to good advantage as show animals and breeding stock. Another approach used by more commercial breeders is to be able to produce a more genetically uniform population of alpacas that are reliably consistent in the desired traits. Although this in some respects might encompass the excellent individual approach, it is more concerned with narrowing the overall range of variation within the population.

Neither of these are necessarily correct, but they serve to illustrate the need for different strategies. A selection programme based on 'anything will do' is likely to make little progress in achieving goals other than breeding alpacas because they are alpacas.

The first step in designing a breeding programme is to define the objectives, and then continually review them as the programme develops. With this in place the next step is in identifying suitable dominant studs which offer high repeatability to their offspring in the desired area. For commercial fibre producing stock we would perhaps be concentrating on fibre density and uniformity of fineness, crimp and lustre.

Record keeping is an essential part of the project. If as breeders we are not keeping measurable data on the heritable traits we require and the environment then we can not hope to achieve much except by chance. The phenotype of an alpaca is the result of its genetic makeup and the environment it lives in. Valid comparisons can only be made like with like.

The parameters of superior breeding stock can be defined by the concepts of dominance, heritability, breeding value and repeatability.

A dominant male stud has the ability to transmit his excellence to the next generation. This means identifying males who are homozygous for the heritable traits that are under selection,' and then to use them as often as possible. The best looking stud with the lowest micron is no guarantee that he is dominant.

Heritability refers to the degree to which an alpaca of superior phenotype can transfer this to his offspring. It gives us an indication of whether selection for that characteristic will be effective. Estimates of heritability for alpacas are not well documented, however some research data from Peru indicates that traits related to fertility and survival have low heritability, production based traits such as a fleece characteristics are moderate to high, and size and body weight are highly heritable. Traits with moderate to high scores suggest that these can achieve gains relatively quickly.

There is also a correlation between heritable traits. A phenotypical correlation estimates the degree of association between two characteristics in the same animal. Data suggests that there is a significant and positive phenotypic correlation between an alpaca's fleece weight and fineness. A selected alpaca with a high fleece weight is more likely to also have a higher than average fibre diameter. Genetic correlation estimates the extent to which selection for one characteristic in a parent will cause a change in another characteristic on the offspring. Selection of parents for high fleece weight might increase the fibre diameter in their offspring if a high positive correlation exists. A negative correlation would indicate the reverse. Although no specific genetic correlation data is available for alpacas it is noted that Australian merinos have a low correlation factor for fleece weight and fibre diameter and that it is possible to hold fibre diameter relatively constant while selecting for weight.

Breeding value is a measure of the ability of a parent to transmit their qualities genetically into their offspring. An alpaca with a high breeding value produces offspring which resemble itself. Repeatability is a measure of the consistency of the relationship between repeated records which measure the phenotypic values of a trait within a population. It is data taken from a population measure rather than from an individual alpaca. For example, measurements taken on fleece weight or fineness are affected by age, season and diet. In selecting alpacas in early life for good fibre characteristics we hope they retain much of this superiority in relation to the average for many years to come.

Finally variability. Based on the rules of Mendelian inheritance all groups of alpacas, if mated randomly will eventually breed to the mean of their genetic merit. On average the herd will resemble the average of their ancestors. A show winning stud male will not necessarily be of strong value for breeding purposes. He might be the product of a lucky mathematical combination of the genes from ordinary parents rather than a solid expression of high quality homozygous traits transmitted from genotypically similar parents. Conversely a rather ordinary stud, a bit small, conformationally not strong but maybe having fine fibre could unknowingly have had a rough start in life providing a disappointing phenotype that hides the strong genetic background of his parents. He would unknowingly be perhaps a better bet for breeding purposes. The difference is simply the relative variability of their ancestors. This variability coupled with genetic selection offers the opportunity to create rapid change for certain heritable traits.

There are three ways of selecting alpacas for breeding. The most common is on the basis of phenotype or look. The second is for selection based on pedigree and an analysis of the ancestry. The final option is to progeny test or make selection decisions based on the dam or sire's production over many breedings. Often parts of all three will be used. As breeders if we take time to understand these concepts and measure the results of our work, we can go a long way in making selection of breeding stock based on genotype rather than phenotype, that is on the basis of locating alpacas with a high proportion of homozygous genes.

Most breeders are rarely in the position to make selection on the basis of one trait. The slow breeding rate and limited number of animals available for a programme forces a number of characteristics to be considered together to achieve an all round improvement. We cannot afford to ignore fleece weight in the pursuit of fineness or conformation, vigour or fertility. How can we therefore combine the phenotype assessment across a number of heritable traits to make correct decisions on genetic make-up. A possible selection method would be designed around a programme based on scoring each alpaca against a set of defined parameters, whose weight in the final score is contoured to match the goals and objectives of the breeding programme. In this way, the average increases or decreases in the performance of offspring can be closely monitored. Those animals achieving higher scores overall can be pulled off to form the basis of breeding for future generations.

Another method is by close analysis of pedigree if this is available. However this does not reveal any information about the offspring and breeding value estimates based purely on pedigree are not consistently accurate.

Once again the only way to determine the true breeding value and dominance of a parent is to research their progeny. The parent's offspring must be measured for the important traits. All offspring must be measured, or a sample used that is truly representative of both the excellent and the not so excellent, and encompassing an environmentally neutral selection. To succeed progeny testing must be applied rigorously, without regard for the absolute quality of an individual alpaca. Accurate record keeping is essential and proper research of all progeny using data recorded by the Registry will assist us all in ensuring such effects. In practice a potential stud male should be bred across at least ten to twenty non related females and then wait for the offspring to mature. In this way a truly excellent male with high breeding value will be exposed allowing him to be used in confidence over many more females. Progeny testing is not just for the large breeder. Small breeders can utilise such data from their own research when making decisions on the choice of studs or in the purchase of foundation breeding stock.

If as alpaca breeders we pursue the identification of breeding value rather than just assessing phenotype we can all make rapid gain in the specific traits we wish to enhance. For the commercial fibre industry we should focus on the cash value characteristics of the fleece but without ignoring the welfare and health areas of vigour, conformation and fertility. In the UK we are at the early stages of being able to assess such data, but it is as well that we start to understand and monitor the performance of our breeding stock on a continual basis. It would be irresponsible and a serious loss to our young industry to ignore such advice when making the important decisions of selection in our breeding programmes.

In the next article I will explain the various methods of breeding strategies that are available to us, and hopefully point out which method we should be using to achieve our goals, whilst ensuring that genetic deformities do not dilute and corrupt our growing national herd.

Chas Brooke - MileEnd Alpacas

Part I, Part III

Classical MileEnd Alpacas - enquiries@alpaca-uk.co.uk - 01884 243 579