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Inbreeding and it’s Effect in Pig Farming

Farmers today let’s share about inbreeding, one of the commonest vices in pig farming.

Meaning of Inbreeding: This is the mating animals of the same breed that are closely related.

Inbreeding is the mating of individuals that are related. In the strict sense, all members of a breed are related. As a result, any seedstock producer is practicing some inbreeding.

Therefore, we generally reserve the term inbreeding for the mating of animals that are more closely related than the average of the breed.

This usually happens to farmers when starting up farms , they have tendencies of buying pigs in pairs not putting it in mind if this pair could be closely related.

The other farmers tend to chose good looking males from a given given furrow and push it to becoming the king of the farm and this bore ends up mating the mother and its sisters.

Inbreeding and it's Effect in Pig Farming


.There is high concentration of common gens for both desirable and undesirable traits i.e: hernia and cryptorchidism .
.There is decrease in litter size
.Increase in mortality
.Low immunity in pigs
.Weak and slow growing pigs
.Low libido for inbreeding sows and bores
. Few eggs during oestrus for gilts hence furrowing small litter

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Why does inbreeding matter?

Passing on undesirable traits to the next generation is directly linked to breeding. The more closely related the parents are, the more frequently these undesirable traits will become phenotypic (result in visible impacts on the pig’s health and productivity).

Line breeding uses the same principles as inbreeding but a desired characteristic is being sought. For most breeders, genetic diversity is the key to producing healthy litters and robust examples of future breeding stock. This isn’t simple when the genetic pool to pick from is small, but it is important.

Fortunately, with modern technology, not only can you find out how related one pedigree pig is to another, you can also use artificial insemination from unrelated boars to assist you in lowering the risk.

A mistake some breeders make is registering multiple boars from the same litter to use as sires. One boar should be the maximum from each litter or you risk producing lots of boars used in others breeding programmes, pushing up the number of litters that are closely-related and thereby failing to expand genetic diversity.

Use different, unrelated AI boars each time you breed. Remember that other breeders will be using those AI boars on their own farms, making some of your herd closely related to others around the country. AI stations do change their boars or add new ones to the list, so take advantage of new genetics.

It is recommended for breed conservation that one individual male should not contribute to more than five percent of future breeding populations therefore it is wise to avoid the most popular AI boar.

Inbreeding and it's Effect in Pig Farming

The co-efficient of inbreeding

In the USA you will often see a pig’s co-efficient of inbreeding (CI) quoted as a percentage and in the UK it is scored as a value between 0 and 0.1. The CI is the probability that a pig with two identical genes received both genes from one parent, and not implicitly that an individual did actually inherit that identical gene.

The more related the mated pigs are, the more likely they will have identical inherited genes (see Table 1). The CI gives a guide as to how related a pig’s parents were to each other and this can be used prior to a mating to calculate the percentage of inbreeding any subsequent piglets would have.

The lower the score of inbreeding, the more likely the piglets will be healthy. As piglets in a litter are not clonal (unless identical twins) and all genes are donated randomly from each parent, CI scores can only be used as a guide and not an absolute.

CI scores are a useful additional tool to use when selecting between equally suitable boars and sows for breeding. It is important to determine any potential of unseen health problems such as sub-fertility and congenital abnormalities appearing in offspring.

Table 1
Table 1 Coefficient of inbreeding between related sows and boars, by degree of relatedness

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Changing your breeding herd CI scores

If you begin to establish greater degrees of ancestral inbreeding – especially if the same common ancestors are shared more than once and on both paternal and maternal sides – the probability of inheriting identical genes increases and therefore the CI score starts to rise considerably.

The impact of recent inbreeding (in the previous two to four generations) is greater than early inbreeding followed by outbreeding. Outbreeding can be used to re-establish genetic diversity in your herds by selecting completely unrelated sows and boars that will produce the lowest CI score in subsequent litters.

Breeders should aim for the lowest CI possible in the subsequent piglets when selecting the parents but accept that it may take a few generations to get down to lower levels.

Various mating schemes of animals are classified under two broad categories — inbreeding and outbreeding. Classification depends on the closeness of the biological relationship between mates. Within each category, a wide variation in intensity of this relationship exists. A very fine line separates the two categories.

Mating closely related animals (for example, parent and offspring, full brother and sister or half brother and sister) is inbreeding. With less closely related animals (first cousins, second cousins), people disagree about where to draw the line between inbreeding and outbreeding.

Technically, inbreeding is defined as the mating of animals more closely related than the average relationship within the breed or population concerned. Matings between animals less closely related than this, then, would constitute outbreeding.

Related: List of Problems Confronting Livestock Production

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