Note: For brevity, the term ‘new breeds‘ is used in this page, though it is not strictly correct. The sheep breeds referred to are those that shed their fleeces and/or have fleeces that are wholly or partly kemp or hair. Some of these sheep have coloured fleeces. The Dohne Merino, the South African Meat Merino (SAMM) and the Afrino are relatively new to Australia but are not included because they are wool producing, non-shedding Merino sheep.
Breeds such as those listed in Table 1 are often collectively called the ‘new’, ‘alternative’ or ‘exotic’ sheep breeds. Most of these breeds are no longer particularly new to Australia and they are no more alternative than any other breeds (they are exotic but so are all the sheep in Australia). Most of these breeds originate from Africa or the Middle East. The Wiltshire Horn and Wiltipoll breeds shed their fleeces annually but they are not usually described as new breeds because the Wiltshire was introduced into Australia from England in 1952 and the Wiltipoll was developed in Australia from 1996. There are some new breeds of fleece-shedding sheep, developed in Australia, but not mentioned in Table 1.
Claims have been made that external parasites do not establish on some new sheep breeds but this is not true. Anecdotal evidence in Western Australia suggests however that lice are less frequently detected on these breeds and their crosses than on woolled, non-shedding breeds. The fleeces and skins of some are quite different from those of a Merino, so perhaps the new breeds are poor hosts for external parasites.
|Breed||Fleece type and colour||Fleece shed annually?|
|Afrikaner||Hairy, kemp free; white (in Australia)||Yes|
|Awassi||Double coated, containing hair, heterotype, wool and kemp fibres; often coloured||No|
|Damara||Outer kempy coat, inner layer of wool; range of colours||Yes|
|Dorper||Wool and kemp; black head with white body, or all white (White Dorper)||Yes|
|Karakul||Double coated; black at birth, greyer with age||No|
|Van Rooy (White Persian)||Hair; all white||Yes|
|Wiltipoll||Double coated; white||Yes|
|Wiltshire Horn||Double coated; white||Yes|
Why treat new breeds for lice?
The direct cost of lice infestation of sheep may be small if their fleeces have little or no market value. However effective lice treatments will probably be required at times for other reasons, such as the following:
- Transfer of lice to or from wool producing sheep. If there are wool producing sheep on the same farm as louse infested, non-wool producing sheep, then treatment of the latter to protect the former will be essential. Conversely, if wool producing sheep have lice and lice eradication is desired, then all sheep on the farm, including any new breeds, will need to be treated.
- Good neighbourly relations. If neighbours with wool producing flocks have (understandable) concerns about the risk of spread of lice infestation to their own sheep.
- Skin and property damage from rubbing. The cost of damage to potentially valuable sheepskins and to fences, gates and other structures, caused by sheep rubbing, can be difficult to quantify but may be important.
- Cockle. Lice can cause a skin allergic response, resulting in a type of skin damage called cockle. This is only apparent when skins are processed. Cockle can reduce the value of high-grade skins, such as those that the new breeds are expected to produce.
Not all itchy sheep are lousy sheep
When any sheep rub or chew at their fleeces, lice infestation is just one of a number of possible causes. Some exotic diseases, such as scrapie, sheep pox, lumpy skin disease, screw worm fly and Aujeszky’s disease may cause sheep to rub or chew their fleeces, among other signs (see biosecurity reminder below).
Sheep that shed their fleeces annually tend to rub when their fleeces are being shed in spring and summer. Other parasites may be responsible for skin irritation, such as itch mites or fly maggots. Grass seeds, photosensitisation of the face and ears following some plant poisonings, or sunburn on the back following shearing may all cause rubbing or the appearance of fleece derangement. Before assuming that itchy, rubbing sheep of any breed are lousy, inspect them carefully and seek expert help if you are uncertain, especially if they are showing other signs of illness.