What do you think of when you imagine a sheep?
Wool, right?
Sheep are raised for meat, milk, and wool.
Although some sheep go through natural shedding, it is a cause for concern when sheep lose their fleece unexpectedly.
Stress from malnutrition, reproduction, and disease all play a role in sheep losing fleece prematurely. The status and quality of its wool are indicators of the sheep’s overall health. The natural shedding cycle also causes wool loss, although domestic animals continually grow fleece rather than seasonally shedding it.
Because people have bred domesticated sheep for wool production, they must be sheared, or they can overheat in the summer or become prey to parasitic species such as ticks, lice, mites, and maggots.
Keep reading to find out more about sheep and wool!
Wool Fiber Growth In Sheep
In sheep, the phases of wool fiber growth are the same as in hair for humans, consisting of the anagen, catagen, telogen, and exogen phases.
In the anagen phase, the hair follicle cells produce the hair, or in this case, wool.
The catagen phase is when the follicle growth finishes and pigmentation and cell growth stops.
The telogen phase is the resting phase, where the wool is not growing but stays in place.
Last, the exogen phase is where the wool falls out, and the anagen phase occurs all over again.
Types of Wool Loss in Sheep
Wool loss is different than outright baldness, or alopecia, in sheep, although a sheep farmer would be concerned about either condition.
Alopecia is the absence of wool from where it normally grows; wool loss is when it fails to grow or thins until the sheep looks bald.
Generalized wool loss and localized wool loss are two aspects of the problem.
Medications, stress, or illness cause generalized wool loss.
Localized wool loss is caused by infections such as Staphylococcus bacteria or injuries.
Wool loss is also from self-inflicted damages from where the sheep rubs on objects or stable materials.
Lambs sleeping or playing on the back of the ewe will also rub off wool.
A phenomenon called wool slip, or Ovine telogen effluvium, gives a patchy, moth-eaten look to the wool.
With this condition, the hair growth cycle of the follicle is disrupted and is not going through the telogen phase.
Skin biopsies will show the wool follicle is in the anagen phase.
Localized or Infectious Causes
Lumpy wool is caused by mycotic dermatitis, or dermo, from the bacterium Dermatophilus congolensis in damp areas where high humidity or rain keep the sheep and bedding material from drying out.
Bacterial dermatitis creates hard scabs and lifts from the skin with the wool, giving it a lumpy look.
It is also common to get a secondary infection with allergic dermatitis.
Another kind of dermatitis is Pelodera dermatitis, caused by the larvae of the free-living saprophytic nematode Pelodera strongyloides.
The larvae invade the hair follicles and cause inflammation and hair loss.
The best way to prevent severe infection is by keeping bedding and the sheep’s living area clean and dry.
Related: What type of bedding is best for sheep?
There are external parasites that cause skin damage and wool loss as well, including:
- Psoroptesovis, sheep scab mite – the later stages of sheep scab cause intense itching, which leads to reduced feeding and loss in body condition and even seizures and death
- Chorioptesovis, foot scab
- Demodexovis, demodectic mite
- Darmalinaovis, the biting louse – these are spread from sheep to sheep via direct contact with each other or with infested places or materials such as tags of wool hanging from branches
- Transmissible Spongiform Encephalitis in sheep also causes wool loss and is called scrapie
Animals treated for infection are vulnerable to reinfection from untreated animals or their environment, such as dirty bedding, if not taken care of.
Studies show animals returning to common grazing are more likely to be reinfected and infected from closer contact during the winter months.
Nutritional Causes
Mineral and protein deficiencies also cause wool loss.
Sheep, mostly ewes, engage in wool-plucking from other sheep’s backs because of deficiencies of:
- Copper
- Zinc
- Cobalt
- Calcium
- Phosphorous
- Sodium chloride
- Manganese
Zinc deficiency causes alopecia and poor wool growth.
Excess selenium causes mild wool loss on the neck and sides of the sheep.
Protein deficiencies play a role in wool loss, although it is more a problem with energy intake than pure protein.
Wild Sheep vs. Domesticated Sheep
While most domesticated sheep have been bred to produce more and thicker wool, wild sheep have not.
Wild sheep shed their wool naturally and rub their bodies against trees to get rid of the extra fleece, leaving wool tags.
Wild sheep do not need shearing, and the fibers they shed are put to good use by birds and other wildlife in making nests.
Most domestic sheep do not shed their winter coats and need human intervention in the form of annual shearing.
Extreme wool-producing breeds, such as the merino, especially depend on humans.
8 domestic, adaptable breeds of sheep do not need shearing, known as “hair sheep.”
Many are derived from African breeds and make good meat goats.
Related: Do sheep shed their wool naturally?
Why Is Wool Loss Important?
Although wool production is only about 1% of the global supply of textile fibers, it is still an important commodity in many communities.
Conditions and diseases causing wool loss affect the quality of the wool and reduce its value.
A reduction in wool growth leads to production losses and less income for the sheep farmer and the community.
Wool is a natural, biodegradable product providing comfort for the consumer and health benefits.
On the farm level, wool loss is indicative of something happening to your sheep.
From stress to medical issues, any good sheep farmer, like you, needs to investigate the cause right away.
When in doubt, don’t hesitate to call a vet either.
It’s always better to be safe than sorry.
