Genotype, Phenotype and the Environment written by Steve Marshall of Stansbury Alpacas
This article has been published in: - Alpaca World Magazine (UK) Issue 22 - Summer 2007 - Town and Country Farmer Magazine (Aust) Vol 24 No 3 Spring 2007
Many alpaca breeders have been romanced by the alluring fleece and regal stance of an alpaca that stands out from the crowd. Recognition in the show ring through ribbons and trophies reassure breeders contemplating paying high prices at auction for such an outstanding alpaca. People regularly purchase alpacas purely on their outward physical appearance and been rewarded with an animal that has made a great impact and had huge genetic gains in one generation of breeding. However, the wise investor would consider more than the physical attributes of that single alpaca, delving into the science that makes up that elite individual. In this article I will explore the links between genotype, environment and phenotype in attempt to provide the reader with a more accurate method of selecting a high quality alpaca for a stud program.
What is Phenotype?
An alpaca’s phenotype is simply the physical appearance of that individual alpaca. It includes such things as the fleece type and colour, size, shape and even temperament. The alpaca can be measured with quantifying figures such as EBVs (Estimated Breeding Values) or by measuring each measurable characteristic against specific performance standards. An alpaca’s phenotype changes as it grows, goes through weaning and develops as a mature animal. The phenotype of an alpaca is what the judge is able to see and consider in a show ring.
What is Genotype?
An alpaca’s genotype is it’s genetic make up. In a broad sense the genotype determines the species of an animal. For example an alpaca’s genotype is always expressed as an alpaca, the same as a horse genotype will always be expressed as a horse. Looking at things a little closer, you can identify an alpaca’s genotype as either Suri or Huacaya and this would be shown in the phenotype. Some parts of its genetic make up you will be able to see and therefore be able to measure in a quantifying manner. A further example in the future may be to identify the genotype of alpacas that produce a particular type of crimp in fleece. Genome mapping as it develops will provide a very reliable way of identifying an alpaca’s genotype. In future it will be possible to identify genes that control eye colour, fleece colour, fleece style, etc. Through DNA testing and genome mapping it will then be a real possibility of identifying alpacas that carry genes for specific characteristics. It could also be in the form of screening out alpacas that carry genes responsible for genetic faults and excluding them from breeding programs. Gene mapping has been completed to a stage in some animals where some genetic faults can be identified in horses, dogs, cats, etc. Research scientists and geneticists working in the field of genome mapping could provide the key to producing genetically sound, fault free alpacas of a particular style as determined by market influences.
Environment and the Equation
The environment plays an enormous part in the physical appearance of an alpaca. The more control of the environment and reduction of variables a breeder can achieve, the more likely they will be in a position to identify alpacas with a superior genotype. That is, the alpaca you see and can physically assess is the sum of it’s genotype or genetic make up and the effect of the environment.
Genotype + Environment = Phenotype
Consider the example of identical twins possessing the same genetic make up but able to exhibit quite different appearances if raised in different environments. One twin may be raised in a sheltered nurturing environment with excellent nutrition and correct mineral balance to appear as close to physically perfect as you have seen. The second twin could have been disowned and relocated at two weeks old surviving on an inadequate bottle formula in a harsh environment where feed and mineral balance was very poor. It may have struggled with sickness and constant infections while it slowly grew out to an almost satisfactory size but looked a sad and sorry excuse for an alpaca. The interesting point here is that both of the identical twins, although not the same in appearance can provide exactly the same genetic input if used in a stud program, however only one would make the show circuit and become noticed. Clearly there are dangers is in reliance on phenotype alone for selection. With the realization that environment can influence up to 60% of the phenotype of an alpaca it becomes very important to limit environmental differences and variables. If environmental differences are minimized the phenotype of an alpaca will more closely match the genotype and therefore increase selection accuracy. Environmental differences also come into play when trying to assess and rank alpacas for potential purchase from different stud locations. One location may have very well balance soil growing highly nutritious feed while the other may have imbalanced soil affecting plant growth and causing mineral deficiencies in the alpacas at that property. The more variable added to the equation, the more difficult it becomes to compare alpacas from different locations.
The Value Genotype and Phenotype
As we all strive to produce the perfect alpaca and the quality from which we are able to select improves, we should consider how to select more accurately. In the near future I suspect alpacas exhibiting an elite phenotype will be divided into three basic categories and valued accordingly.
The first category will include alpacas of outstanding phenotype that have a pedigree with a mix of highly respected and famous names. Without any specific selection criteria that are applied to alpacas in the pedigree it is likely that an alpaca in this category is a biological fluke and combination of random genes. These alpacas could produce progeny displaying similar characteristics however, due to the random selection of elite alpacas in the pedigree they could just as likely produce progeny of quite varying quality.
The second category will include alpacas of outstanding phenotype and have a pedigree with a mix of highly respected and famous names chosen for their outstanding qualities and similar characteristics. Alpacas in this category would be reasonably likely to breed true to type because through selecting for similar characteristics the chance of having alpacas with similar genes increases. The greater emphasis on selection for a particular type (fleece style, conformation, etc.) should make this alpaca worth more than in the previous category.
The third category will include alpacas of outstanding phenotype and have a pedigree that includes highly respected and famous names with similar characteristics but also includes some degree of linebreeding. In this case the breeder has considered the phenotype of alpacas included in the pedigree but also has considered the genotype. By using strict selection criteria, selecting for similar characteristics and including some common ancestors an alpaca in this category is more likely to be able to pass on desired traits. If an alpaca has even a small degree of linebreeding the chance of it carrying two genes responsible for a particular trait is increased. An alpaca breeder concerned with breeding elite alpacas is more likely to value the prepotency of an alpaca in this category due to the higher degree of reliability when used in a breeding program.
Stansbury Alpacas P. O. Box 195 Inglewood, South Australia, 5133 + 61 883 805 965 firstname.lastname@example.org