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Thursday, May 27, 2010

Add on Infomation - Pembiakan Arnab

Salam Sejahtera.......dah lama rasanya tak update blog aku nak share sikit pasal info yang aku baca dalam dunia tanpa sempadan nih....walaupun tak la paham 100%, at least dapat la menambah pengetahuan dalam penternakan arnab harap pengunjung dapat manfaat....tq

Basic Information Needed To Breed Rabbits Successfully
              Firstly we must define two basic terms, phenotype and genotype. The phenotype of an animal refers to the physical characteristics of that animal (what we see). The genotype refers to only that part of the animal that is due to his genes (amino acids that transfer the messages from parents to offspring). There are two primary reasons for the differences we see in animals, differences due to environment and differences due to the genes that the animals are carrying. Most breeders have little or no control of their gene pool. These would be phenotype breeders. They use little scientific approach to their breeding programs. And as we know, even a blind squirrel finds an acorn now and then. A consistently successful breeding program will usually make use of some form of linebreeding. This is breeding genotype.

What is linebreeding?

                 Linebreeding is a simple concept that can be made to seem complicated. One must remember that linebreeding is a program that produces animals from a single line of descent and from a common ancestor. It is a long ranged plan that a breeder is required to have an ideal animal firmly fixed and must be willing to pursue that ideal regardless of any breeding fads that might dictate otherwise.
                Linebreeding is built on the principle of "breeding like to like to get like." It affords the serious rabbit breeder the opportunity to set a type in the shortest amount of time. It also “narrows the gene pool.”
The greatest danger in a linebreeding program is that it intensifies all of the genes--good and bad. In other words, if you have a line of inherently quality show rabbits, breeding like to like—quality to quality--should result in an higher quality line of rabbits.
              If, at the same time, this line of rabbits consistently lacks depth, then breeding like to like should result in an intensified line of poor-depth rabbits. In a linebreeding program, you, as the breeder, find out what is good and bad about your program in a hurry. The only way to offset the intensification of undesirable traits in a linebreeding program is to ruthlessly cull the undesirables from the herd
           With linebreeding the breeder must use selection as a rigid tool in the process. Unless this is adhered to, the breeder will never attain his goal and the program will be doomed to failure. There are very few constructive linebreeding programs and very few bloodlines that can be successfully linebred. The characteristics that must be maintained are conformation, soundness, fertility, disposition, coat color, refinement, and females that exhibit the ability to raise healthy babies.

How should I begin?
             The most significant part of the selection process begins with the foundation buck and foundation does that have common ancestry with the foundation buck. This will make the journey towards the ideal animal shorter. Otherwise the breeder will experience extra generations of breeding if the ancestry is not common among the foundation bucks and does. Many breeders of success believe that the does are the strongest part of the linebreeding program and the bucks are providers of the necessary genes to improve the line.
              The first step in linebreeding is the mating of half-brothers and half-sisters that are produced by mating the foundation buck with the foundation does. The result of the half brother and half sister matings will be the second generation with the resulting offspring being double grandsons and double granddaughters. If the foundation does held common ancestry with the foundation buck uniformity would be apparent.
          One must not try to linebreed to more than one common ancestor. The double grandsons and granddaughters will be genetic sons and daughters of the foundation sire. If each parent gave the next generation 50% of their genes, the double grandsons and granddaughters would carry 50% of the genes of the foundation sire. But because of the random division of genes in the parents, the influence of the four grandparents may not be transmitted in equal proportions. The offspring may bear a relationship to any one of the grandparents greater or less than the normal 25% relationship.

Is inbreeding different from linebreeding and is it important?

There have been many questions asked of inbreeding, its safety and benefits. Maybe I can shed some light on this subject.

             Definition: Inbreeding is the mating of animals that are more closely related than the average degree of relationship within the population. Linebreeding is the strategic use of inbreeding to improve traits found in one family line. The math used in linebreeding is not very difficult, but it is quite interesting. The inbreeding coefficient is a percentage of the probable chance that genes will double when related animals are mated. It is often used in determining whether or not to mate two related animals because the higher the inbreeding coefficient is, the more likely it is that genes will double, whether they be good or bad.
               Basically inbreeding is an intensified form of linebreeding, with the sole difference being in the genetic closeness of the rabbits being bred to each other.
                Among the advantages of inbreeding, is that it affords the surest and quickest method of fixing and perpetuating a desirable characteristic or group of characteristics, it tends to create lines or strains of animals that are uniform in type, and it keeps the closest possible relationship to a desirable ancestor.
The disadvantages of inbreeding are that it almost certainly increases the proportion of undesirable breeding stock, with genetic abnormalities often appearing with increased frequency.

What to bred to what?

               The different inbreeding coefficients are related to the different kinds of matings. In a half-first cousin mating, 1 common grandparent, the inbreeding coefficient is 3.12%. First cousin matings, 2 common grandparents, have a 6.25% inbreeding coefficient. Both grandparent-grand offspring and half-sibling matings have an inbreeding coefficient of 12.5%. Parent-offspring matings and full-sibling matings, for 1 generation, have an inbreeding coefficient of 25%. Two generation full-sibling matings have an inbreeding coefficient of 37.5% and full-sibling matings for 3 generations have an inbreeding coefficient of 50%.

              By considering the inbreeding coefficient, breeder can determine whether or not it will be beneficial for them to linebreed two animals. Inbreeding usually has a deleterious effect on many production characteristics. This is particularly important if the level of inbreeding increases rapidly. Where the rate of increase is slow then selection can be made to eliminate undesirable types and low producers. Inbreeding is particularly significant in the formation of new breeds where the original gene pool needs to be large enough so the undesirable types can be culled.

To put inbreeding into perspective the following table gives the rise in inbreeding for some close matings.

Full brother-sister mating 25%
Half brother-sister mating 12.5%
Father-daughter/mother-son 25%
Grand dam-grandson 12.5%
Common grandparents (cousins) 6.25%

Thus, inbreeding can have genetic advantages but care must be taken so not to detract from favorable characteristics already established.

What is crossbreeding and how should it be used?

              Crossbreeding (outcrossing or outbreeding) is the opposite of inbreeding, i.e.: increasing the number of heterozygous pairs. This is commonly known as “widening the gene pool.” Outbreeding is the mating of animals, which are less related than the average relationship of the population. Thus outbreeding is practiced most commonly between families.

               In crossbreeding, heterosis or hybrid vigor is often a common calculation in determining whether or not to cross two breeds. Heterosis is the degree to which an offspring deviates from its parent's breeds
Of the two breeding methods, outcrossing involves the least amount of risk. By mating rabbits that are unrelated, the chance of intensifying undesirable traits is minimized.
Unfortunately, due to the heterozygous, or dissimilar, genetic nature of a group of unrelated rabbits, the chance of intensifying desirable traits is likewise diminished.
              The breeder's craft comes into play here; in honestly and accurately assessing the strengths and weaknesses of the breeding herd, and making the crosses that will accentuate the strengths and offset the weaknesses.
Often times, the most consistent results in an outcrossing program are obtained when the outcross buck is, himself, a strongly linebred individual
               To carry the outcrossing method one step, or generations, farther, once an outcross is made within a heterozygous herd of rabbits, the results are a generation of rabbits that carry 50 percent of the same blood. If the outcross has been successful, the offspring should resemble each other to a greater degree than do their unrelated dams.
               The next challenge lies in finding the best possible outcross buck to breed the first generation does to. The ultimate goal would be to find a buck that "nicks"(not a real scientific term but it gets the point across) with the does.
              So called successful nicking is due, genetically speaking, to the fact that the right combinations of genes for good characters are contributed by each parent, although each of the parents within itself may be lacking in certain genes necessary for excellence.
In other words, the animals nicked well because their respective combinations of good genes were such as to complement each other.
                 I must be quick to point out, however, that all outstanding animals arising from this method of breeding should be carefully scrutinized from a breeding standpoint, because, with their heterozygous origins, it is unlikely that they will breed true.
                 Whether you decide to build your program on the principles of outcrossing or linebreeding, or a combination of the two, it is important to remember that, scientific discoveries notwithstanding, rabbit breeding remains much more of an acquired craft than an applied science.
There is no secret, and there is no magic formula. It's knowing your rabbits, studying them every day and being honest with yourself when it comes time to make your breeding decisions.