Expression of worm resistance in sheep selected for low worm-egg counts fed at maintenance or above-maintenance level

J. C. Greeff, S. M. Liu, D. G. Palmer, L. J.E. Karlsson

Research output: Contribution to journalArticle

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.

Original languageEnglish
JournalAnimal Production Science
DOIs
Publication statusE-pub ahead of print - 6 May 2019

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Ovum
Sheep
Maintenance
sheep
Trichostrongylus colubriformis
Teladorsagia circumcincta
restricted feeding
Diet
body weight
diet
Trichostrongylus
Eggs
Larva
necropsy
flocks
developmental stages
larvae
Infection
infection

Cite this

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title = "Expression of worm resistance in sheep selected for low worm-egg counts fed at maintenance or above-maintenance level",
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.",
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Expression of worm resistance in sheep selected for low worm-egg counts fed at maintenance or above-maintenance level. / Greeff, J. C.; Liu, S. M.; Palmer, D. G.; Karlsson, L. J.E.

In: Animal Production Science, 06.05.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Expression of worm resistance in sheep selected for low worm-egg counts fed at maintenance or above-maintenance level

AU - Greeff, J. C.

AU - Liu, S. M.

AU - Palmer, D. G.

AU - Karlsson, L. J.E.

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Y1 - 2019/5/6

N2 - 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.

AB - 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.

KW - gastrointestinal nematodes

KW - Merino

KW - nutrition

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DO - 10.1071/AN18552

M3 - Article

JO - Australian Journal of Experimental Agriculture

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SN - 0816-1089

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