Fifteen worm-free @entity742 (two-and-a-half to three months or four to four-and-a-half months old) were infected with 3500 or 4000 Ostertagia ostertagi larvae on five days each week for six weeks, and their performance compared to that of controls. Eleven @entity742 were killed after eight weeks and four were challenged with @entity24651 to determine whether any cross resistance had developed. A feature of the O ostertagi @entity281 was the considerable variation in response. Overall liveweight gain was lowered by 24 per cent in the two-and-a-half to three-month-old infected @entity742 , mainly due to reductions of 27 to 40 per cent in four of the seven @entity742 . There was no consistent effect in the older @entity742 . The worm populations consisted mainly of early fourth stage larvae and developing worms, but a small percentage reached sexual maturity and these produced a low faecal egg count (1 to 63 eggs per gram). Numerous intraluminal refractive crystals were present in the gut of both @entity5294 and developing stages, possibly reflecting degenerative changes. @entity1184 of the @entity5932 with patchy loss of differentiation was a feature of the @entity281 , and in four lambs serum pepsinogen concentrations were elevated. Exposure to O ostertagi did confer some protection against challenge with @entity24651 in that worm counts were reduced to about 60 per cent of those in controls, although no increase was observed in the numbers of arrested larvae. The successful passage of O ostertagi through young @entity742 could be important in mixed or alternate grazing systems by providing a reservoir of @entity281 for the alternate host.

Effect of Ostertagia ostertagi on lamb performance and cross resistance to XXXX .

@entity24651 :: ('45464', 'Species') :: ['O circumcincta'] @entity742 :: ('9940', 'Species') :: ['lambs'] @entity1184 :: ('MESH:D006984', 'Disease') :: ['Hypertrophy'] @entity5932 :: ('MESH:C565008', 'Disease') :: ['abomasal mucosa'] @entity281 :: ('MESH:D007239', 'Disease') :: ['infection'] @entity5294 :: ('MESH:D004320', 'Disease') :: ['adult worms']
@entity24651 :: (45464,Species) :: ['O circumcincta']
