Evaluation of the effects of nematode parasitism on grazing behaviour, herbage intake and growth in young grazing cattle

Forbes, Andrew Benjamin; Huckle, C. A.; Gibb, M. J.; Rook, A. J.; Nuthall, R.

doi:10.1016/s0304-4017(00)00218-1

Cited by 77 publications

(40 citation statements)

References 15 publications

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“…For example, the highest level of infection with abomasal nematodes in our study was only 4000 (in an un-aged female) and the mean was less than 1000, compared to Soay sheep and Svalbard reindeer which would typically be around 10 000 adult abomasal nematodes (Gulland, 1992 ;Wilson et al 2004). The lower levels of body fat and lighter body weights in this wild herbivore are consistent with the effects found in domestic animal studies where reduced growth and poor condition is attributed to reduced food intake caused by inappetance and reduced food assimilation due to pathogenic effects of the nematodes on gut function (Fox, 1993(Fox, , 1997Arneberg et al 1996 ;Forbes et al 2000).…”

Section: Discussionsupporting

confidence: 83%

Low-level parasitic worm burdens may reduce body condition in free-ranging red deer (Cervus elaphus)

Irvine

Corbishley²,

Pilkington

et al. 2006

Parasitology

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Regulation of ungulate populations by parasites relies on establishing a density-dependent relationship between infection and vital demographic rates which may act through the effect of parasites on body condition. We examine evidence for parasite impacts in 285 red deer (Cervus elaphus) harvested during 1991 and 1992 on the Isle of Rum. In the abomasa, prevalence of nematodes was 100% and the most abundant genus observed were Ostertagia species, however, mean intensity of infection was low (less than 1000) relative to other studies. Additional species, also present in low numbers, included Nematodirus spp., Capillaria spp., Cooperia spp., Monieza expanza, Oesophagostomum venulosum and Trichuris ovis. Lungworm (Dictyocaulus spp.) and tissue worm (Elaphostronygylus cervi) larvae were also observed in faecal samples. There was no evidence for acquired immunity to abomasal nematodes. Despite low levels of infection, both adult male and female deer showed significant negative correlation between indices of condition (kidney fat index, dressed carcass weight and larder weight) and intensity of Ostertagia spp. infection. However, there was no evidence that pregnancy rate in females was related to intensity of infection. For calves, there was no relationship between body condition and intensity of infection. The apparent subclinical effects of low-level parasite infection on red deer performance could alternatively be due to animals in poorer nutritional state being more susceptible to infection. Either way the results suggest that further studies of wild populations are justified, in particular where high local host densities exist or alternative ungulate hosts are present, and, where experimental treatments are tractable.

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Section: Discussionsupporting

confidence: 83%

Low-level parasitic worm burdens may reduce body condition in free-ranging red deer (Cervus elaphus)

Irvine

Corbishley²,

Pilkington

et al. 2006

Parasitology

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“…protein) requirements. In addition to the endogenous protein loss and the increased resource requirements, a reduction in appetite and feed intake accompanies infection (Fox et al., 1989, Forbes et al., 2000, Kyriazakis, 2014). Although complex, the mechanism for inappetance in ostertagiosis was modelled as a function of the rate of immune acquisition, as it has been suggested that this reduction is associated with components of the immune response (e.g.…”

Section: Methodsmentioning

confidence: 99%

Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves

Berk

Laurenson

Forbes

et al. 2016

International Journal for Parasitology: Drugs and Drug Resistan

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The development of anthelmintic resistance by helminths can be slowed by maintaining refugia on pasture or in untreated hosts. Targeted selective treatments (TST) may achieve this through the treatment only of individuals that would benefit most from anthelmintic, according to certain criteria. However TST consequences on cattle are uncertain, mainly due to difficulties of comparison between alternative strategies. We developed a mathematical model to compare: 1) the most ‘beneficial’ indicator for treatment selection and 2) the method of selection of calves exposed to Ostertagia ostertagi, i.e. treating a fixed percentage of the population with the lowest (or highest) indicator values versus treating individuals who exceed (or are below) a given indicator threshold. The indicators evaluated were average daily gain (ADG), faecal egg counts (FEC), plasma pepsinogen, combined FEC and plasma pepsinogen, versus random selection of individuals. Treatment success was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The optimal indicator in terms of BPR for fixed percentages of calves treated was plasma pepsinogen and the worst ADG; in the latter case treatment was applied to some individuals who were not in need of treatment. The reverse was found when calves were treated according to threshold criteria, with ADG being the best target indicator for treatment. This was also the most beneficial strategy overall, with a significantly higher BPR value than any other strategy, but its degree of success depended on the chosen threshold of the indicator. The study shows strong support for TST, with all strategies showing improvements on calves treated selectively, compared with whole-herd treatment at 3, 8, 13 weeks post-turnout. The developed model appeared capable of assessing the consequences of other TST strategies on calf populations.

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“…In grazing herbivores, parasitism can induce inappetence, reduction in grazing time and changes in grazing behaviour [37]–[40]. The extent of this parasite induced anorexia will vary with the degree of pathological changes and the parasites’ sites of predilection within the host [38]. This anorexia leads to intake reductions of between 30 and 60%, compared with uninfected animals [41]–[43].…”

Section: Introductionmentioning

confidence: 99%

Modelling Parasite Transmission in a Grazing System: The Importance of Host Behaviour and Immunity

et al. 2013

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Parasitic helminths present one of the most pervasive challenges to grazing herbivores. Many macro-parasite transmission models focus on host physiological defence strategies, omitting more complex interactions between hosts and their environments. This work represents the first model that integrates both the behavioural and physiological elements of gastro-intestinal nematode transmission dynamics in a managed grazing system. A spatially explicit, individual-based, stochastic model is developed, that incorporates both the hosts’ immunological responses to parasitism, and key grazing behaviours including faecal avoidance. The results demonstrate that grazing behaviour affects both the timing and intensity of parasite outbreaks, through generating spatial heterogeneity in parasite risk and nutritional resources, and changing the timing of exposure to the parasites’ free-living stages. The influence of grazing behaviour varies with the host-parasite combination, dependent on the development times of different parasite species and variations in host immune response. Our outputs include the counterintuitive finding that under certain conditions perceived parasite avoidance behaviours (faecal avoidance) can increase parasite risk, for certain host-parasite combinations. Through incorporating the two-way interaction between infection dynamics and grazing behaviour, the potential benefits of parasite-induced anorexia are also demonstrated. Hosts with phenotypic plasticity in grazing behaviour, that make grazing decisions dependent on current parasite burden, can reduce infection with minimal loss of intake over the grazing season. This paper explores how both host behaviours and immunity influence macro-parasite transmission in a spatially and temporally heterogeneous environment. The magnitude and timing of parasite outbreaks is influenced by host immunity and behaviour, and the interactions between them; the incorporation of both regulatory processes is required to fully understand transmission dynamics. Understanding of both physiological and behavioural defence strategies will aid the development of novel approaches for control.

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Evaluation of the effects of nematode parasitism on grazing behaviour, herbage intake and growth in young grazing cattle

Cited by 77 publications

References 15 publications

Low-level parasitic worm burdens may reduce body condition in free-ranging red deer (Cervus elaphus)

Low-level parasitic worm burdens may reduce body condition in free-ranging red deer (Cervus elaphus)

Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves

Modelling Parasite Transmission in a Grazing System: The Importance of Host Behaviour and Immunity

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