Why Do Sheep Need Shearing? How a Sheep's Wool Keeps Growing

Why does a sheep’s wool keep growing?

The wild ancestor of the sheep, the Asiatic mouflon, has a coat like a deer’s. Long, coarse guard hairs called kemp cover a short, soft undercoat of wool. Each spring the mouflon molts, shedding the winter undercoat in patches so it does not overheat in summer.

The first domestic sheep, kept from about 10,500 years ago, still had this hairy coat. Over thousands of years, farmers kept the animals with the softest, thickest wool and bred from them. Breeding gradually replaced most of the coarse kemp with fine wool fibers and, crucially, removed the seasonal molt. In most modern wool breeds, the wool follicles in the skin keep growing fiber all year round.

Wool is made of keratin, the same protein found in human hair and nails. Each fiber is crimped, or wavy, which traps air and makes wool warm, springy and good at shedding rain. A fine-wool Merino has many more wool follicles per square centimeter of skin than a hair sheep, producing a dense fleece.

What happens if a sheep is not shorn?

A wool sheep that is never shorn simply keeps growing its fleece. Over several years this causes real welfare problems:

• Overheating. A thick fleece insulates so well that a sheep can struggle to keep cool in summer.
• Flies and dirt. Wet, dirty wool around the tail attracts blowflies, whose maggots can infest the skin, a condition called flystrike.
• Movement and sight. Heavy wool can drag on the legs and cover the eyes, a problem called wool blindness in breeds with woolly faces.
• Getting stuck. A sheep weighed down by wool is more likely to roll onto its back in a dip and be unable to get up, which shepherds call being cast.

This is why shearing is a normal yearly event for wool flocks around the world.

The story of Shrek and Chris

Two famous runaway Merinos show how much wool a sheep can grow. Shrek, a Merino wether in New Zealand, hid in caves and avoided the annual muster for six years. When he was finally caught and shorn on national television in 2004, his fleece weighed about 27 kg (60 lb), enough wool for around 20 men’s suits. He became a national celebrity and lived to about 16.

In 2015, a stray Merino named Chris was found near Canberra, Australia, after probably five or more years without shearing. His fleece weighed about 41 kg (90 lb), several times a normal fleece, and was confirmed by Guinness World Records as the heaviest ever shorn from a sheep. He had struggled to walk under the weight and recovered at an animal sanctuary afterward.

By comparison, a normal annual Merino fleece weighs about 4–5 kg (9–11 lb).

Sheep that shed their own wool

Not every sheep needs shearing. Several groups still molt naturally:

Primitive breeds. The Soay sheep of St Kilda, off the west coast of Scotland, sheds its brown fleece each spring, and many Shetland and North Ronaldsay sheep partly do the same. In Shetland the loose wool was traditionally plucked off by hand, a practice called rooing, which does not hurt the sheep because the fibers are already loose.

Hair sheep. Breeds such as the Dorper from South Africa, the Katahdin from Maine in the US, the Barbados Blackbelly and the St. Croix grow a coat of hair with a light undercoat that falls out each year. The Wiltshire Horn is a British breed that sheds its short fleece naturally. Hair sheep are kept mainly for meat, and many farmers have switched to them because coarse wool now sells for less than the cost of shearing.

When and how are sheep shorn?

Most flocks in Europe and North America are shorn once a year in late spring or early summer, after the coldest weather but before the heat and fly season. Some flocks that lamb indoors are shorn in winter, before lambing, instead. Some long-wool breeds, such as the Lincoln and Cotswold, may be shorn twice a year.

A skilled professional shearer removes the fleece in one piece in a couple of minutes, using electric clippers and a set pattern of strokes that keeps the sheep calm and avoids cuts. In Australia and New Zealand, shearing gangs travel between farms each season, and competitive shearing is a popular sport.

Is shearing good for sheep?

For modern wool breeds, regular shearing is necessary for their health and comfort, because they cannot shed on their own. Animal welfare groups such as the RSPCA support shearing done calmly by trained shearers, while campaigning against rough handling. The real issue is the breeding history that created a non-shedding coat, which is one reason interest in self-shedding breeds is growing.

Sheep are not the only animals shorn for fiber. Alpacas also grow a fleece that is clipped once a year, as explained in What is alpaca wool?.