The goal of any breeding facility should be to produce animals of quality and, in the long run, improve the breed as a whole to the point that all of the animals are of high quality. In order to reach this goal, there are several methods of breeding that can help the breed flourish. Line breeding and inbreeding both can be beneficial if the right foundation is used. On the other hand, overuse of line breeding can lead to inbreeding and if not carefully supervised, can turn on you and produce all the wrong traits.

Linebreeding is inevitable in some breeds (such as the miniature donkey) where a small gene pool of foundation stock is involved. Be it 6 animals or 100, those foundation animals must be bred to one another and their offspring crossed back, over a period of time until the population grows in size. Look at a miniature donkey with a 5 to 6 generation pedigree and you are likely to see *Luigi 95 in the pedigree. He was one of the original imports, and the source of the sorrel color in miniatures today. You might even see his name on the sheet more than once. If you see his name 3 or 4 times in the whole pedigree, that can be considered linebreeding.

So, where does linebreeding end and inbreeding begin? It all has to do with the concentration of bloodlines you are using. By tradition, breeders have considered distantly related crosses to be Linebred while close-up crosses were Inbred.

Inbreeding is a technique where animals that are closely related are bred back to each other. These include father-daughter pairs, mother-son combinations, or even brother-sister. Inbreeding in the strictest scientific definition also means all crosses that are duplicated on both sides of a pedigree (sire and dam). Therefore if *Luigi 95 was the grandsire top and bottom, this in inbreeding, no matter how distant the duplication is on paper.

The good side of line and inbreeding is that you can try to select the best traits. Good head, good hip, cross back to a closely related animal and have a great foal with the best of both worlds. Your super-jack can now be outcrossed to unrelated jennets and pass on his genes to future generations.

The bad side is that all the little faults, the recessive genes, have suddenly been crossed back in. Remember from last issue our discussion that it takes 2 doses of a recessive? Homozygous is two doses of an identical gene (BB) and heterozygous is one dose each of different but paired genes (Bb). All animals have some kind of recessive genes. If your A jack has a recessive for an underbite for example, and his full sister B jennet also has the recessive (and these can be hidden for many generations), you have suddenly increased the chances not only for future foals to carry the bad gene, but for them to get the underbite themselves as well. You have increased the changes of Homozygous pairing in the genes.

Although at times the goal is to produce animals with homozygous genes, some homozygotes should be avoided. Doubles doses of the sorrel gene for example, are the only way to get sorrel, and a homozygous spotted jack would guarantee all his foals would be spotted, but would you really want to assure that every foal from your jennet would have weak loins and an overbite in addition?

The dangers of inbreeding and the “bad” recessives could mean that a foal in born with all kinds of faults, from being just plain ugly to real deformities. If a breeder is going to practise inbreeding, they should be aware of the consequences. Are you willing to put down a newborn or very young foal because it has legs so deformed it cannot stand, or a cleft palate (hole in the roof of its mouth)? Yes, expensive horses have had corrective surgery for this kind of thing, but are you willing to go to the time & expense? Surgery might correct the problem physically but genetically, where it counts, the fault is still there. It’s not that donkeys are inferior to horses and don’t deserve to have the best of care, but can we afford to continue breeding animals with severe faults? This is why culling poor stock from herds, and making sure that pet-quality animals are pets only, and not bred, is important.

If you decide that your stick is of good enough quality to use in line-breeding or inbreeding (by a physical exam of conformation & temperament), then by all means study the pedigree closely. If you know you already have a large amount of concentration on one side, but the other is “untraced,” you might think again before breeding this animal back to their mother, father, son, or daughter. You might get “the Great One,” but remember at the same time you’re also gambling with the unknown on that untraced side. Henceforth another reason to make sure that you register your animals and keep track of bloodlines.

Arabian Horse breeders use linebreeding with success, but Arabians also have strict pedigree rules. Theirs is a closed book meaning only purebred foals from registered purebred parents may be called Arabians. The ADMS don’t want to close the books on donkeys. You can’t confuse a donkey with any other breed the way you might confuse some Arabs with certain types of Morgans for example, or some lines of Quarter Horses with Thoroughbreds. A donkey is a donkey no matter the size or color. But we would like in the future to be able to have different breed sections, with pedigree backing wherever possible, and for those pedigrees to be able to show that donkey breeding is a carefully planned process just as it is in other breeds.

Below are some examples to help illustrate the points made in this article. The pedigrees shown are all real scenarios although the names have been altered to protect the actual animals and their owners.

We begin with “Monica” who shows no evidence of inbreeding or line breeding. There is no duplication of names showing in her 5-generation pedigree. If you wished to cross her with an animal that also had a “Lance” as a Great-great grandparent, it would be far enough removed that it would not even be considered line breeding.

“Kissee” shows line breeding. The concentration of “Tootsie” is 12.5% (in the Great-grandparent field) and “Mr. Ben” is concentrated to 18.75% (in the Great-great Grandparent line). The normal percentage should be 6.25% for each great-great grandparent.

“Bucky” shows where the line starts to get fuzzy between linebreeding and inbreeding. If there were 6 generations, and “Peanut” kept showing up throughout, then you could say he was linebred for “Peanut.” In reality, both “Jack” and “Jenny” have the same sire (“D. Joe”). This makes the concentration of “D.Joe” blood at 50%. If you look at the concentration of “Peanut” it is at 25% - half the total blood line contributed by the 4 great-grandsire slots.

“Lil Bit” is inbred. Her parents are full brother and sister. If you break it down, “Lil Bit” really has 50% “Icee” and 50% “Melody” blood. This is where all those dangerous recessives can start to crop up. It would not be a good idea to breed “Lil Bit” to any animal with “Icee” or “Melody” up close in the pedigree, and even the great-grandparent blood should be avoided since there is such a high concentration already. An untraced animal should likewise be avoided since you would have no way of knowing if any of these animals would be in that background.

“Lass” has a degree of inbreeding, but it is far enough removed in her pedigree it ought to be okay to cross her back to an animal with “Shorty” back in the breeding. Breeding to an animal with “Shorty” up closer - like the grandsire - would be line breeding, but hedges on inbreeding. This is when careful visual examination of the animals involved (especially the parents) and any other offspring they have produced is necessary. If there are faults starting to crop up, then it is essential to go to outside, unrelated bloodlines.

This last example is either a worst case or absolute best case of inbreeding, depending on whether you’re a half empty or half full kind of person. With a limited gene pool, this type of breeding might be necessary, but it is more likely to produce serious faults. The resulting animal should absolutely NOT be bred to those with any duplicate bloodlines. If you break this down, “Extreme” is not really 50% “Jed” and 50% “Delia,” but rather more like 50% “Frosty” and 50% “Missy.” To make matters worse, the full percentage of male input, top and bottom, is “Kevin.” This animal has no genetic diversity in the male portion of the pedigree and this is not good.

By making sure your animals are registered, you can keep the breed records more complete. Having untraced in the middle of a pedigree might mean you are unknowingly duplicating bloodlines. Should color be a consideration in linebreeding? Linebreeding perhaps, but inbreeding for color might otherwise be sacrificing conformation. The best bet always seems to be to breed the best, and geld the rest. No jack who is not of the best conformation, regardless of the degree of inbreeding, should be considered as a breeding jack. There are far too many fair and mid-range jacks available. Every effort to use only the best jacks for breeding should be taken.

(This Page last updated: September 21, 2004