Vet on call: Common birth defects in pigs

Saturday February 9 2019

David Njoroge feeds piglets in a farm in Nakuru.

David Njoroge feeds piglets in a farm in Nakuru. Pig farmers should note that there are myriads of birth defects that may be observed in the animals and the good news is that the abnormalities are rare if farmers exercise good practices in pig production. PHOTO | JOHN NJOROGE | NMG 

DR JOSEPH MUGACHIA
By DR JOSEPH MUGACHIA
More by this Author

Joy had been waiting for three months, three weeks, and three days or what we call the 3-3-3 wait for her gilts to farrow.

She had diligently selected her breeding stock, including the boar, except for one gilt she had bought from another farm to boost the number of breeding mothers.

She had realised her resident boars were related to the new gilt. Mating the pig with the boars would, therefore, have resulted in inbreeding.

The new gilt was very promising as she conceived on the first mating and had carried the pregnancy to term without incidence.

She unfortunately dropped a bundle of trouble last week. She delivered 13 piglets with the eyelids sealed together tightly. The piglets were all essentially blind.

When Joy called me, she was frustrated by the outcome. “Doctor, is there any known occurrence of piglets being born blind like puppies and kittens?” She enquired.

She further explained the situation with her piglets and said some were moving round in circles like though they had brain disease. Seven piglets had already died because they were unable to suckle well.

The other four gilts had farrowed perfect piglets that were all active and in good health. Joy and her staff had tried to force the eyes open by pulling the eyelids apart but they could not separate since they were tightly attached.

I was not aware of any situation where piglets are born with eyelids sealed and then they open later in life. After she gave me the full history of the gilt and the boar, as she had been given by the farms that had owned them, I requested her to send me photos of the piglets.

From the photos, the eyes appeared well-formed but the eyelids had failed to develop separately and open. I had never encountered the condition in my more than 30 years of practice. However, some medical conditions are rare and unpredictable.

I checked with my veterinary colleagues, pig farmers and documented literature, but did not find any evidence of a similar observation.

CHANGES IN GENES

I shared the general birth deformities seen in domestic animals in my article on January 20, 2018 available online. The observation on Joy’s farm motivated me to specifically explain the common birth deformities that pig farmers may see on their farms and how to minimise their occurrence.

Animals that give birth to many young ones and frequently like pigs, dogs and cats are good models for observing birth deformities.

In general, however, birth deformities are rare. They are caused by genetic problems, environmental factors or a combination of both.

The most common cause of birth deformities are genetic problems arising from breeding closely related lines of animals. This is termed inbreeding.

The other cause is genetic problems caused by changes in the genes called mutations. Mutations may be caused by faults in the multiplication of the body cells or damage caused by environmental factors whether physical like force or heat, chemical like toxins or infectious agents like viruses.

For farmers and scientists to understand the cause of birth defects, a systematic investigation is required. This can be done at the farm level by asking critical questions as follows.

Are all the affected animals of one breed or one sire (father)? If the answer is “yes”, then the deformity is likely genetic.
Second, is the condition appearing in offsprings of one sire and every group of piglets affected?

Again, if the answer is in the affirmative, then the condition is most likely genetic.

Third, are the affected animals born of closely related parents? An affirmative answer indicates genetic deformity due to inbreeding.

Lastly, were the parents of the affected group of piglets under the same environment, nutrition and management conditions during mating and pregnancy? If the answer is “yes”, then the condition is unlikely to be caused by genetic factors. It may be caused by environmental, nutritional or management factors.

GENETIC DEFECT

From the criteria of the four questions and the history of the piglets that Joy gave, I diagnosed genetic factors possibly caused by inbreeding since Joy had no proper history of the boar and gilt breeding.

The nervous signs and death seen in some piglets were caused by low glucose level in the blood due to inability to feed. I advised her to destroy the remaining piglets and breed the sow again with a boar of a known breeding history.

Joy had the option of attempting to raise the remaining piglets by hand-rearing. This is where the pigs are helped by a worker to suckle.

They are also taken to the feeding trough to eat and given water by hand. This rearing is uneconomical because it is expensive and the pigs will take a long time to mature.

Furthermore, animals with one observable genetic defect may also be having other internal defects that only become apparent later in life.

Some birth defects are commonly observed in pigs due to inbreeding. Scrotal hernia occurs when the intestines enter the scrotum and appear as a swelling in piglets.

Umbilical hernia is seen when the intestines form a swelling under the scar of the umbilical stamp. Some piglets are born with the anus closed, a condition called atresia ani. The three conditions may be corrected by surgery and the animals live to maturity but they must not be used for breeding.

Other defects can also be observed frequently due to inbreeding or genetic mutation and they require no intervention.

Hermaphroditism occurs when pigs are born with both male and female reproductive traits and organs. Such animals grow to maturity but must not be bred.

Cryptorchids are male piglets born with one or both testicles retained inside the abdominal cavity. When both testicles are in the body, such pigs are sterile. Such should never be bred.

AVOID INBREEDING

Some female piglets are born with nipples that are inverted and therefore cannot allow milk flow after farrowing. Other piglets are born having tremors (jumping pig disease) due to developmental defects caused by viral infections of the foetus.

Spraddle legs occurs when both hind and fore limbs are uncontrollable and they may spread out making the piglet unable to stand.

The condition is caused by underdevelopment of the muscles that pull the legs inward close to the body but the cause of the underdevelopment is unknown.

Pig farmers should note that there are myriads of birth defects that may be observed in the animals. The good news, though, is that the abnormalities are rare if farmers exercise good practices in pig production.

To prevent the birth defects, farmers should avoid inbreeding by keeping up-to-date records and only mating unrelated animals.

They should also ensure that all animals that show birth defects, however, slight, are not used for breeding to avoid amplifying the defective genes with subsequent offsprings.

Farmers should also ensure the pigs are fed balanced diet containing all the recommended nutrients in the right quantities.

Finally, the farmers should ensure they practice recommended disease control measures and maintain the appropriate physical conditions for their pigs such as good hygienic housing and temperature control.