by Steve Marshall Stansbury Alpacas
by Steve Marshall Stansbury Alpacas
P. O. Box 195, Inglewood, South Australia, 5133 + 61 883 805 965 firstname.lastname@example.org
Most alpaca breeders have experienced at some stage mating two alpacas to produce an outstanding offspring. Having achieved a good result the first time it seems reasonable to expect the same again. Some breeders have gone as far as to duplicate the combination multiple times through embryo transfer. However due to a random combination of genes the second attempt was disappointing with a less than satisfactory result. Observing inconsistent results from various breeders led me to focus on developing a strain or line of quality alpacas that breed true to type as one of my foundation breeding objectives.
At this stage I should make it clear that I am not a geneticist. Nor do have any formal qualifications in animal breeding. I am simply an alpaca breeder with a desire to breed quality alpacas consistently. My interest in linebreeding stemmed from observations of Australian sheep and cattle studs with paddocks full of livestock that looked identical. I couldnít help but be impressed with the consistency of the livestock they breed. Upon closer inspection I found that each stud breeder had developed a clearly identifiable trait, type or strain within their breed. These breeders developed bloodlines that are respected within their industry and genetics that are sought after by others. My goal was to achieve this for Stansbury Alpacas. My wife Joanne raised the concept of linebreeding presenting me with examples. It wasnít to long before I was hooked, researching and reading everything I could find on linebreeding. I found information on linebreeding everything from mice to dogs, horses, cattle, sheep, alpacas and even cheetahs. Examples of inbreeding and linebreeding various animals such as dogs, cattle, goats, sheep and horses are able to provide us with the benefit of years of experience and knowledge that we can apply to alpaca breeding. At this stage it is worth remembering that linebreeding is not an exact science. Total control is not obtainable however predictability may be greatly increased through a scientific approach and a sound breeding plan.
Linebreeding Ė what is it?
By definition linebreeding is a concentration of the genes of a specific ancestor or ancestors through their appearance multiple times in a pedigree. In essence it usually involves choosing a specific target ancestor and selectively breeding so that the target ancestor appears multiple times in a pedigree. Inbreeding can be similar but involves the breeding of extremely close relatives. Some would argued that linebreeding is inbreeding, but to a lesser extent. However, I think it is important to recognize the difference because some of the problems I will highlight later are clearly associated with inbreeding but not linebreeding. Keeping track of the inbreeding coefficient and maintaining a coefficient of 12.5% or less is a safe and simple way to check that you are linebreeding and not inbreeding. With multiple generations of linebreeding you may approach 20% but it is wise to achieve no more than a 12.5% gain in any one generation.
Examples of linebreeding combinations
Sire to a granddaughter would achieve a 12.5% inbreeding coefficient.
This is particularly useful to breeders that own a stud male of exceptional quality that they wish to use as a target ancestor to fix certain traits in their herd.
Son to a granddaughter would achieve a 6.25% inbreeding coefficient.
Half brother to half sister would be a 12.5% inbreeding coefficient.
These last two examples may be achieved without having access to the target ancestor. Any breeder can identify a particular target ancestor that they donít necessarily have access to and line breed to it. You can even linebreed to an alpaca that is dead or in another country so long as you have access to a significant number of progeny.
Examples of inbreeding combinations
Sire to daughter achieving a 25% inbreeding coefficient.
Full brother to full sister would also achieve 25% inbreeding coefficient.
I do not recommend inbreeding. As you can see the percentage inbreeding coefficient rises very quickly if mating very close relatives and is likely to reveal severe faults with little warning that you are developing an unsustainable line or strain. Keeping track of pedigrees, monitor levels of inbreeding and various traits is extremely important and there is a variety of software available to achieve this. An understanding of Wrightís Inbreeding Coefficient and Galtonís Law of Ancestral Hereditary is also very useful in making decisions about any breeding program.
Why linebreed? The advantages
The most obvious reason is to develop consistency and uniformity within a herd. By selecting and breeding the best progeny of a specific target ancestor it is possible to set or fix those desired traits and characteristics within a herd. Linebreeding causes an increase in the proportion of like genes and therefore increased uniformity. In fact with linebreeding you are increasing homozygosity for various selected characteristics.
As homozygosity for various traits increases through linebreeding a breeder is able to more accurately and reliably predict what the offspring will look like. A carefully considered breeding plan can be a wise investment on what genetic material is passed on to the next generation. Selective linebreeding can reduce the odds in your favour and assist you in achieving your breeding objectives with more reliability. When a pedigree develops with the target ancestor appearing multiple times, homozygosity for desired traits increase and the phenotype more closely matches the genotype. That is, the physical appearance of the alpaca more closely matches the genetic make up. This is a very important factor that can easily be underestimated. Environment can play a huge part in the physical appearance that is the phenotype, of an alpaca. I have heard of figures estimating up to 60 or 70% being environmental influence. Itís a little scary to consider investing a lot of money on a particular alpaca based on its appearance alone. Does it have the genetic background and have the consistency to back up its appearance? Was it a biological fluke due to a random combination of genes that canít be repeated? If used as a stud male will it pass on the desired visible traits or is it a Pandoraís Box with the genetic diversity to produce virtually anything? A carefully planed linebreeding program can stack the odds in your favour with alpacas that have a physical appearance more closely matching their genetic make up or genotype.
If it isnít enough to have alpacas that look like they are meant to according to their pedigree, then consider prepotency. Some stud males of exceptional quality are prepotent for their exhibited, desired traits such as fleece type and quality, while others are not. If prepotent they are likely to pass on the desired characteristics to their progeny. Having a look at the show results for the progeny of a particular stud male can provide you with some trends. However, this can easily provide a distorted picture due to differing levels of show participation by various breeders. Prepotency for desired traits is an important selection criteria when considering any stud male.
As a linebreeding program progresses and the target ancestor appears multiple times in a pedigree an alpaca is more likely to carry genes for selected traits in a homozygous form. That is pairs of genes that are the same for selected traits. Through linebreeding we have the ability to reduce the variety of genes, therefore increasing an alpacaís prepotency for selected traits. This is one of the factors that really swayed me towards linebreeding. Linebreeding has provided me with the ability to produce alpacas that are more likely to exhibit and pass on the characteristics that are important to my breeding goals. Increasing prepotency for selected, desired traits will give a breeder the ability and confidence to more accurately and reliably predict the phenotype, physical appearance of future generations.
Inbreeding problems and disadvantages
The gains of consistency and uniformity within a herd due to linebreeding are because of a reduction in the variety of genes. As the variation within the gene pool of a herd becomes smaller, hybrid vigor is reduced and therefore a corresponding increase of inbreeding depression occurs. A carefully planned linebreeding program can to a large extent avoid the effects of inbreeding depression through wise selection. However, mating of extremely close relatives, that is inbreeding, will lead to inbreeding depression and reduce hybrid vigor within a few generations.
Inbreeding depression is linked to reduced resistance to disease and infection, lack of fertility, increased mortality rates and the appearance of genetic faults. Outcrossing is a very simple method of increasing hybrid vigor and maintaining robust, healthy alpacas which I will discuss a little later.
An alpaca carries 37 chromosome pairs inheriting 37 from the dam and 37 from the sire. If the two genes an alpaca carries for a particular trait or fault on a chromosome pair are the same it is said to be homozygous for that trait or fault and will pass on this genetic information to its progeny. Defective genes responsible for the appearance of genetic faults are usually recessive and masked by a dominant counterpart. The practice of linebreeding does not create defective genes responsible for a particular fault any more than mating two highly unrelated alpacas. Linebreeding and inbreeding does increase the likelihood that recessive genes responsible for a particular fault will be uncovered due to increased homozygosity and the reduction of gene combinations. If both parents pass on a recessive gene for a defect then the offspring will exhibit the defect.
Most alpaca breeders in Australia are continually outcrossing, mating as far as possible unrelated alpacas. This practice will generally mask or hide faulty, defective genes allowing them to be propagated in the carrier state and spread widely among the Australian Alpaca population. While I am sure no one wants to breed alpacas with genetic faults, inbreeding and to a certain degree linebreeding will allow a breeder to identify alpacas and bloodlines that carry recessive defective genes and eliminate them from a breeding program. The ultimate goal would be to have developed a line or strain that is genetically sound, free from recessive defective genes that cause faults. Current DNA research in alpaca genome mapping has huge potential and could be very valuable step forward in identifying alpacas that carry genes responsible for faults before they are using in a breeding program.
Selection and culling
Selection has a major role to play in any breeding program and has great influence in future generations. It is usually not appropriate to choose a stud male for instance based on a superb fleece or fantastic conformation or a good looking head, in isolation to other traits. It is easy to be influenced by the success of currents fads, but to achieve uniformity within a herd a breeder must stick to breeding objectives and stringent selection criteria. Culling works hand in hand with selection in a breeding program and is equally important. Culling may be achieved through, not breeding from particular alpacas, using females that exhibit undesirable traits as recipients for embryo transfer recipients, castrating males that do not match breeding objectives, etc, etc. A breeder that is willing to remove animals from a breeding program that do not match the breeding objective will achieve whole herd genetic gain quickly.
If a breeder is not happy with the alpaca they have produced outcrossing is frequently used to bring in different genes and reduce homozygosity. By breeding to an unrelated line new genes and new traits are immediately brought into the mix. The new genes can also increase hybrid vigor and address any areas affected by inbreeding depression in one generation. There are different ways to outcross. However, if your goal is to maintain consistency and uniformity it is a good idea to outcross to an unrelated line that has some degree of linebreeding while also exhibiting the traits you desire. Uniformity within a herd can still be maintained when crossing two lines that have some degree of linebreeding, however, these uniform alpacas are unlikely to produce uniform and consistent progeny. Therefore it is important to either continue breeding back to the original line or continue with the new line to maintain uniformity and consistency in future generations.
I expect soon an alpaca with several generations of linebreeding will be worth considerably more than an one that has a good phenotype achieved through outcrossing. This is due to the higher level of prepotency that is likelihood of passing on visible traits and years invested in planned linebreeding. Linebreeding is a slow process and requires the breeder to have very clear goals and selection criteria for success.