Effect of the sheep body louse (Damalinia ovis) on host weight gain and fleece value

Abstract

Sheep body lice were normally present in low numbers in summer that built up in autumn, peaked in winter, and declined in spring.Body lice appeared tv favour sites along the mid-sides and back of their host and occurred least frequently on the abdomen.There was no evidence to suggest that, under the conditions such as those of this trial. low to moderate numben of body lice will significantly reduce the rate of body-weight gain or fleece production. but wool quality may be significantly reduced.

Effects of sheep lice(Damalinia ovis)on wool colour

“…This belief has been supported by the results of a trial by Kettle & Pearce (1974) where it was found that, on the basis of subjective assessment, the quality of wool from lousy sheep run in parallel with a louse-free mob was significantly lowered.…”

“…On each of these 20 animals, 26 sites (13 on each side) were examined by making 2 partings about 10 cm long in each area. Each site was scored as '1' if lice were present, thereby giving a possible score of 0-26 (Kettle & Pearce 1974).…”

Recovery of sheep lice (Damalinia ovis) from baled wool: A technique enabling nation-wide surveillance of louse ridden flocks

“…Value would also be lost because of reduced wool 'quality'. 'Quality' is difficult to assess, but has been shown, on the basis of subjective assessment, to be adversely affected by sheep lice (Kettle & Pearce 1974). In addition, 2 aspects of 'quality' which can be accurately measured using scoured woolyellowness and lightness -are both detrimentally affected by lice (Kettle & Lukies 1982b).…”

“…Lice are not randomly distributed over the sheep's body but favour sites along the mid-sides and back (Scott 1952;Kettle & Pearce 1974). Their distribution can best be described as 'contagious' or 'over-dispersed' (as defined by Southwood 1966).…”

“…However, when they are present in substantial numbers, they can reduce the 'quality' of wool produced (Kettle & Pearce 1974;Kettle & Lukies 1982a, b).…”