How to control inbreeding menace

Moses Mutua examines rabbits in his farm in Ongata Rongai, Nairobi. The animals are among those that are prone to inbreeeding. FILE PHOTO | NATION MEDIA GROUP

What you need to know:

  • Inbreeding is the mating of animals that are more closely related than the average relationship within the breed or population. Animals are considered to be closely related when they share common parents, grandparents or even great grandparents.
  • Inbreeding is associated with reduced performance of the offspring. Repeated mating of closely related animals produces progenies that are inferior to their ancestors in terms of the quality and quantity of their output (milk, meat and eggs, among others).
  • Though inbreeding is discouraged, over the years, it has been used by animal breeders to enhance positive traits in a breed.

Many livestock farmers desire to rear the best animals from a certain breed. After having identified and selected a particular breed, the next challenge for the farmer is to ensure he maintains a flock of high-performing animals.

However, the farmer faces the problem of inbreeding. Interestingly, many farmers are unaware or ignorant of this threat.

WHAT IS INBREEDING?

Inbreeding is the mating of animals that are more closely related than the average relationship within the breed or population. Animals are considered to be closely related when they share common parents, grandparents or even great grandparents.

Inbreeding is discouraged even in human beings. Throughout history, man had rules that prohibited close relatives from marrying and bearing children. Though human beings have these norms, many farmers tend to ignore the fact that the same concept applies to animals. The probability of getting closely related animals in Kenya is quite high even among exotic breeds. This is because most of them came from small populations and have only been multiplied but basically retain the same genetic makeup.

WHY IS INBREEDING DISCOURAGED?

Inbreeding is associated with reduced performance of the offspring. Repeated mating of closely related animals produces progenies that are inferior to their ancestors in terms of the quality and quantity of their output (milk, meat and eggs, among others).

This is mainly due to lack of variety in the gene pool and possible erosion of the good traits that the ancestors had. Low productivity translates to low earnings for the farmer.

Inbreeding has also been associated with higher mortality rates, lower growth rates, higher frequency of hereditary abnormalities and inherited disease conditions in the offspring than in the forebears.

Additionally, in case of certain weaknesses or abnormalities in the ancestors, these will become more pronounced in their offspring when they repeatedly reproduce amongst themselves. Inbred animals also tend to exhibit loss of the vigour associated with a particular breed.

Inbreeding is most likely to happen when a farmer keeps a few animals in an enclosed area where they randomly mate. Lack of mating partners from other populations or absence of artificial insemination (AI) services increases the chances of animals mating with their parents, siblings and other ‘close relatives’.

It has been observed that the closer the relationship, the higher the percentage of risk of transmitting unfavourable genes. This phenomenon will eventually have negative results especially if the genes carry unwanted traits such as low disease resistance, poor yields and small size.

WAYS TO CONTROL INBREEDING

One of the easiest ways to avoid inbreeding is by ensuring that animals are sourced from diverse populations within the breed. Buying all your stock from the same farm where mating may not be controlled puts you at the risk of having closely related animals.

It is important that you scrutinise the records of the animal breeder to understand the ancestry of the animal. Most good breeders should avail such records and actually use them as a marketing tool.

It is difficult to establish the genetic makeup of animals with no pedigree records. This also makes it difficult to predict their performance.

A farmer should also ensure that mating within the herd or flock is controlled. Allow only certain males to mate with specific unrelated females.

Keeping records of this will manage future matings of their offspring. It is always advisable to introduce unrelated animals from other farms to boost the genetic quality of your herd. The most important thing in this simple but important exercise is to maintain accurate and complete records.

Where natural mating is not used, AI is a novel method of controlling inbreeding. Suppliers of the semen used in AI usually indicate the ancestry of the sire. Though you will access this information when the extension officer services your animal, keep your own records. AI is the most convenient method as the farmer is presented with a large selection of sires to choose from. Another advantage of using AI is that farmers - can at a slightly higher price - get semen from sires even from outside the country. This further reduces the risk of having related parents.

THE FLIP SIDE

Though inbreeding is discouraged, over the years, it has been used by animal breeders to enhance positive traits in a breed. Through inbreeding, breeders are able to produce uniform predictable offspring. Breeders also use the same technique to make unwanted genes that carry undesirable traits prominent so that they can be eliminated for future generations of the breed.
This, however, is the preserve of professional breeders who have access to modern technology. The average farmer is not advised to carry out such exercises on their own.

Dr Muchunguh is a livestock expert