Role of host and environment in mediating reduced gastrointestinal nematode infections in sheep due to intensive rotational grazing

Colvin, A.F.; Walkden‐Brown, Stephen W.; Knox, Malcolm

doi:10.1016/j.vetpar.2011.08.027

Cited by 18 publications

(18 citation statements)

References 25 publications

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“…The experiment provided strong support for the proposition that IRG (farmlet C) does provide more effective control of gastrointestinal nematodes as evidenced by significantly lower WEC counts and anthelmintic treatment frequency. As reported elsewhere (Colvin et al 2012) this effect is mediated by reduced larval challenge on pasture, rather than improved host resistance. Indeed host resistance to worms was lower on farmlet C due to reduced exposure.…”

Section: Discussionsupporting

confidence: 66%

“…Importantly, these effects were greatest when WEC and anthelmintic treatment numbers were highest, between 2003 and 2005, and this farmlet also did not have the haemonchosis-associated mortality observed in December 2004 on the other two farmlets. Working with a subset of the data from the present experiment, Colvin et al (2008) also reported this beneficial effect of IRG on worm control and in a later report (Colvin et al 2012) showed that the effect of IRG was mediated by reduced larval challenge on pastures rather than improved host resistance to nematode infection. Indeed sheep in the IRG treatment exhibited increased susceptibility to larval challenge in that study.…”

Section: Discussionsupporting

confidence: 52%

“…It should be noted that, in practice, these spelling times will overestimate the decrease in larval populations on pasture as L 3 may continue to develop and appear on pasture for several weeks following removal of stock, particularly in the case of T. colubriformis and T. circumcincta (O'Connor et al 2006). The improved level of control of worms on farmlet C was associated with significantly increased susceptibility to worm infection (Colvin et al 2012) and reduced animal productivity as shown by reduced liveweights (Hinch et al 2013a) and fat scores (Hinch et al 2013b) of livestock on this farmlet relative to those on farmlets A and B. The long rest periods and lower levels of soil fertility on farmlet C were found to be associated with lower levels of both legume and pasture digestibility within this farmlet (Shakhane et al 2013) and these are likely to have contributed to the reduced productivity.…”

Section: Discussionmentioning

confidence: 99%

“…Healey et al (2004) examined the WEC data for the first 3 years of the experiment and reported that clear farmlet differences emerged in 2003, the third year of the experiment, with the main finding being reduced WEC and frequency of treatment on farmlet C. Colvin et al (2008), using monthly samples from lambs, hoggets and ewes over 2 years on each farmlet, demonstrated that IRG of farmlet C can indeed assist in the control of gastrointestinal nematodosis, especially where H. contortus is the most common parasite. A companion paper (Colvin et al 2012) reported that the observed effects of IRG were due to disruption of the parasite lifecycle outside of the host, rather than differences in host immunity. Indeed, sheep on farmlet C were significantly more susceptible to worms than those on farmlets A or B during spring and summer.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

et al. 2013

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Abstract. Managing infections of sheep with gastrointestinal nematode parasites (worms) and problems of resistance to anthelmintic treatments continue to be major challenges for graziers on the Northern Tablelands of New South Wales, Australia. The whole-farmlet study of grazing enterprises undertaken by the Cicerone Project tested the broad hypotheses that compared with typical management (farmlet B), internal parasites can be more effectively managed with improved nutrition (farmlet A) or by intensive rotational grazing (farmlet C). Further aims were to identify the major sources of variation in faecal worm egg count (WEC) over the 6-year period and to examine the efficacy of the various anthelmintic treatments used during the experiment. This paper describes the management of sheep worms at the whole-farmlet level during the experiment, and analyses data from the routine WEC monitoring (5644 records) and larval differentiation tests (322 records) carried out on behalf of the Cicerone Management Board and by a doctoral candidate. It complements more detailed investigations published elsewhere.Over the period from July 2000 to December 2006, worm infections in ewes, lambs, hoggets and wethers were, with some exceptions, successfully controlled on the farmlets through a combination of regular monitoring of WEC, treatment with a wide array of anthelmintics and grazing management. Farmlet C had lower mean WEC (444 epg) and annual anthelmintic treatment frequency (3.1 treatments/year) over the whole experimental period than farmlets B (1122 epg, 4.3 treatments/year) or A (1374 epg, 4.7 treatments/year). The main factors influencing WEC were the time since the last anthelmintic treatment, and the anthelmintic used at that treatment. The magnitude of these effects dwarfed those of climatic and management factors that might be expected to influence the epidemiology of gastrointestinal nematode infections via environmental or host-mediated mechanisms. Nevertheless management factors associated with stocking rate and grazed proportion (proportion of each farmlet grazed at any one time), and climatic indicators of both temperature and moisture availability had significant effects on WEC.The results show that, in a region with Haemonchus contortus as the major sheep nematode, improved host nutrition in a higher input system (farmlet A) did not provide more effective control of gastrointestinal nematodes than typical management (farmlet B); however, it was observed that gastrointestinal nematode control was no worse on farmlet A than on farmlet B in spite of farmlet A supporting a 48% higher stocking rate by later in the trial period (2005). The study provided strong support for the proposition that intensive rotational grazing (farmlet C) provides more effective control of gastrointestinal nematodes than typical management (farmlet B) as evidenced by significantly lower WEC counts and anthelmintic treatment frequency. Tactical worm control based on routine monitoring of WEC provided adequate control of worms on all three ...

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Section: Discussionsupporting

confidence: 66%

Section: Discussionsupporting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

et al. 2013

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“…Prior to the publication of this Special Issue, three refereed journal papers (Behrendt et al 2006;Colvin et al 2008Colvin et al , 2012 and seven conference papers (Hall et al 2001;Scott 2003aScott , 2003bScott , 2006Gaden et al 2004;Healey et al 2004) had been published on different aspects of the Cicerone Project.…”

Section: Publicationsmentioning

confidence: 99%

Delivering extension and adult learning outcomes from the Cicerone Project by ‘comparing, measuring, learning and adopting'

Edwards

Gaden²,

Marchant

et al. 2013

Anim. Prod. Sci.

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Abstract. The Cicerone Project was a partnership between livestock producers, researchers and extension specialists on the Northern Tablelands of New South Wales, Australia that investigated several complex grazing enterprise issues between 1998 and 2006. It was conducted as a Participatory Action Research project, which first surveyed livestock producers to learn of their problems and then carried out investigations according to the Project's chosen motto of 'compare -measure -learn -adopt'. The Project included research into footrot diagnosis and an investigation of whole-farmlet livestock and pasture management systems complemented by a multi-faceted extension and education component, which delivered findings to a wide array of stakeholders across the Northern Tablelands and adjacent regions. This paper describes the extension and education methods and outcomes and reflects on how successful the engagement of livestock producers was through a partnership, which focussed on co-learning by all participants. Several different communication approaches were used including the production of 40 newsletters and the delivery of 61 field days. Collaborators also held two symposia, which presented comprehensive overviews of the research results. In the final year of the Project, a roadshow was held to communicate results to a wider audience in neighbouring districts.The results of the two footrot trials, which were conducted as Participatory Action Research projects, led to rapid and substantial changes in the testing regime for virulent footrot, resulting in large savings for livestock producers through more accurate detection of the disease. Other valued extension and industry outcomes were the ability to compare the biophysical and economic performance of different whole farmlets, an appreciation of the value of the whole-farm system approach, the trustworthiness of the results and the stimulation of livestock producers to think more deeply about their management systems, stocking rate and risk.The Project benefited from the research efforts of four postgraduate students and was of benefit to~300 high school and technical college students and also some 500 university undergraduate students who undertook learning projects in conjunction with Project members and collaborators. This Special Issue of 24 journal papers represents a substantial delivery of the findings from this complex agroecosystem Project, which broke new ground in terms of securing much closer working relationships between livestock producers, scientists and extension specialists. Ultimately, this volume will allow extension of the results of the Cicerone Project to reach a wider audience than has typically been achieved through other Participatory Action Research projects.

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Effect of Selenium Yeast Supplementation on Naturally Acquired Parasitic Infection in Ewes

Hooper

Bobe

Vorachek

et al. 2014

Biol Trace Elem Res

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Gastrointestinal parasites cause substantial economic losses in pasture-based sheep production systems. Supranutritional organic selenium (Se) supplementation may be beneficial because it improves immune responses to pathogens. To evaluate the effect of Se-yeast supplementation on gastrointestinal parasite load, 30 ewes per treatment group were drenched weekly with no Se, 4.9 mg Se/week as Se yeast (maximum FDA-allowed concentration), or supranutritional concentrations of Se yeast (14.7 and 24.5 mg Se/week) starting early fall for 85 weeks. Fecal samples were collected at weeks 63, 66, 78, and 84 and counted for total trichostrongyle-type eggs and Haemonchus contortus eggs (in samples with ≥200 trichostrongyle eggs/g feces). During breeding season (fall), ewes were kept on pasture; ewes receiving 24.5 mg Se/week had lower fecal trichostrongyle egg counts (93 ± 40 eggs/g feces) compared with ewes receiving no Se (537 ± 257 eggs/g feces; P = 0.007) or ewes receiving 4.9 mg Se/week as Se yeast (398 ± 208 eggs/g feces; P = 0.03). In winter, fecal trichostrongyle egg counts decreased, and group differences were not apparent. During lambing season (spring), ewes were kept in the barn and fecal trichostrongyle egg counts increased, although no group differences were observed. However, none of the ewes receiving supranutritional Se yeast, and with trichostrongyle egg counts ≥200 eggs/g of feces, but four of the ewes receiving lower Se dosages had H. contortus egg counts ≥1,000 eggs/g feces (P = 0.04). Our results suggest that supranutritional Se-yeast supplementation may enhance resistance to naturally occurring H. contortus gastrointestinal parasitism in sheep.

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Role of host and environment in mediating reduced gastrointestinal nematode infections in sheep due to intensive rotational grazing

Cited by 18 publications

References 25 publications

Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

Delivering extension and adult learning outcomes from the Cicerone Project by ‘comparing, measuring, learning and adopting'

Effect of Selenium Yeast Supplementation on Naturally Acquired Parasitic Infection in Ewes

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