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- Title
Expression of worm resistance in sheep selected for low worm-egg counts fed at maintenance or above-maintenance level.
- Authors
Greeff, J. C.; Liu, S. M.; Palmer, D. G.; Karlsson, L. J. E.
- Abstract
The present study reports on changes in faecal worm-egg counts (WEC), larval composition, and the number of worms at different developmental stages in young sheep sourced from a flock selected for reduced faecal worm-egg counts over 15 years. The sheep were individually penned and fed a maintenance (1.0 M) or a 1.5 times maintenance (1.5 M) diet over two periods, namely, worm-free and infection phases. They were dosed weekly with 10 000 Trichostrongylus colubriformis and 10 000 Teladorsagia circumcincta L3 infective larvae for 11 weeks. Sheep on the 1.5 M diet had lower WEC and higher bodyweights than did sheep on the 1.0 M diet. A significant decline in the percentage T. colubriformis occurred during the experiment, but no concomitant change in T. circumcincta was noticed. Resistant sheep had significantly (P < 0.001) fewer worms at necropsy, and also shed significantly (P < 0.001) fewer worm eggs during the experiment. Restricted feeding reduced bodyweight significantly (P < 0.001) and had a small but significant (P < 0.04) effect on the faecal worm-egg output and on the number of T. colubriformis worms (P < 0.01) in both the control and resistant sheep. The study showed that sheep selected for low WEC resulted in significantly (P < 0.001) lower WEC than in an unselected control line fed at a maintenance (1.0 M) and at an above-maintenance (1.5 M) level. Restricted feeding reduced bodyweight and had a small negative, and inconsistent, effect on the faecal worm-egg output in both the control and resistant lines. Feeding level can affect the expression of immunity against gastrointestinal parasites. The present study was carried out to determine how important feeding level is in sheep that were bred to be resistant to intestinal worms in comparison to unselected control sheep. The results show that both resistant and control sheep will develop immunity against intestinal parasites, but that genetic differences are much more important than feeding level.
- Subjects
SHEEP diseases; SHEEP; WORM eggs; INTESTINAL parasites; WORMS
- Publication
Animal Production Science, 2019, Vol 59, Issue 10, p1783
- ISSN
1836-0939
- Publication type
Article
- DOI
10.1071/AN18552