A simulation model to investigate interactions between first season grazing calves and Ostertagia ostertagi

Berk, Zoe; Bishop, Stephen; Forbes, Andrew Benjamin; Kyriazakis, Ι.

doi:10.1016/j.vetpar.2016.05.001

Cited by 16 publications

(35 citation statements)

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“…The current model was based on the simulation approach of Berk et al., 2016a, Berk et al., 2016b, which aims to predict the effects of parasitism with O. ostertagi on a population of growing calves, taking into account host phenotype, host-parasite interactions and parasite epidemiology. The model has been further developed here to account for anthelmintic resistance amongst nematodes, by considering the susceptibility of each nematode genotype to anthelmintic treatment.…”

Section: Methodsmentioning

confidence: 99%

“…Remaining resources were then allocated between growth and immunity, proportional to their requirements (Kahn et al., 2000, Doeschl-Wilson et al., 2008, Laurenson et al., 2011). The model was parameterised such that the calf and its growth represented a weaned, castrated male (steer) Limousin x Holstein Friesian born in autumn (Berk et al., 2016a). …”

Section: Methodsmentioning

confidence: 99%

“…Simulation modelling on the other hand may offer an effective alternative, and be highly beneficial in assessing the feasibility of novel control strategies. Here we address these gaps, by developing and using a simulation model that represents calf - Ostertagia ostertagi interactions and the epidemiology of the infection (Berk et al., 2016a, Berk et al., 2016b), in order to test the effectiveness of different TST approaches. O. ostertagi is the parasite of greatest significance in cattle grazing in temperate climates, and as the developed model is stochastic, it allows us to make predictions for the application of TST in a population of calves.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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 usual proposed solution to these problems is to assume that resource requirements for (1) and (2) can be represented as increases in maintenance requirements; the remaining resources are then allocated to growth according to the principles detailed above (Kyriazakis and Houdijk, 2007;Sandberg et al, 2006). There are more elaborate mechanisms that have been assumed to apply to the partitioning of nutrient resources in animals subjected to health challenges (Berk et al, 2016;Doeschl-Wilson et al, 2008;Laurenson et al, 2011). Predicting the limitations in the growth of animals with altered health status remains one of the most challenging fields of research in modelling to date.…”

Section: Growth-limiting Health Conditionsmentioning

confidence: 99%

Feed evaluation science

Filipe

Leinonen

Kyriazakis

2018

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The principles and a quantitative theory of growth for monogastric livestock animals are described here, focusing on the period from birth to slaughter. The theory helps to understand key relationships between the outcomes that may be desired in a production system and their influencing factors, e.g. nutritional, genetic, and environmental, and forms the basis of current mechanistic models for predicting animal performance. We describe general physical, chemical and biological principles that should underlie any description of animal growth; and address growth as a three-faceted problem: 1) growth under 'normal' conditions; 2) growth under 'limiting' conditions; and 3) recovery growth when 'normal' conditions are restored. We propose a theoretical framework that incorporates these situations as facets of a whole, that encompasses growth conditions across modern livestock production systems, and in which terms such as 'normal' and 'limiting' acquire a meaning. To make this framework quantitative, we apply a body of theoretical and empirical principles in the derivation of mathematical models of growth. The usefulness of existing theories and mathematical models depends on the availability of data for testing hypotheses and parameterising models under a range of conditions. A challenge ahead, therefore, is in obtaining extensive data for further testing and consolidating modelling prediction of growth under a wide range of conditions, or as animals respond to change in limitations. Another challenge lies in addressing practical problems posed by heterogeneity in performance within groups of animals: i.e., how to manage groups towards optimal resource use and performance, and how to identify best phenotypical characteristics within breeds, strains, etc. and predict their performance. Further progress will require much greater availability of rich individual data cross-sectioning herds and breeds.

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“…Ostertagia ostertagi infections are one of the main concerns in the cattle industry in England (Bellet et al, 2016;Berk et al, 2016). Extensive negative effects of cattle helminths have been reported, including loss in milk production, decreased growth performances, impaired reproduction, and poor welfare (Sanchez et al, 2002a;Charlier et al, 2014;Bellet et al, 2016); moreover, cattle infected with helminths produce more greenhouse gases (Rushton and Bruce, 2017).…”

Section: Introductionmentioning

confidence: 99%

A longitudinal study of gastrointestinal parasites in English dairy farms. Practices and factors associated with first lactation heifer exposure to Ostertagia ostertagi on pasture

Bellet

Green

Bradley

et al. 2018

Journal of Dairy Science

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The gastrointestinal nematode Ostertagia ostertagi is an important cause of lost production, health, and welfare in cattle. Detailed records were obtained over a 5-yr period (2010-2015) by questionnaires and qualitative interviews to investigate the practices adopted by dairy farmers to control cattle helminth infections and the factors associated with heifer exposure to O. ostertagi on pasture. In total, 1,454 heifers' individual milk samples were collected over a 1-yr period (2014-2015) in 43 dairy farms in England and tested for O. ostertagi antibody by ELISA. Multilevel linear regression models were used to investigate the association between individual milk optical density ratio (ODR) against O. ostertagi and heifer management from birth to time of sampling. Farm and heifer median ODR against O. ostertagi were 0.98 (interquartile range = 0.76-1.02) and 0.64 (interquartile range = 0.42-0.84), respectively. The majority of heifers (88%) received an anthelmintic treatment before sampling in this study. After controlling for the effect of anthelmintic treatments, heifer individual milk ODR against O. ostertagi significantly increased with high stocking rate at first grazing and co-grazing with adult cows before calving. Conversely, heifer individual milk ODR against O. ostertagi significantly decreased when heifers had co-grazed with sheep and pasture grass had frequently been mowed. Overall, these results provide evidence to support targeting grazing management toward limiting the use of anthelmintics in dairy young stock to enable sustainable control of cattle helminth infections in England. However, to be accepted and adopted by farmers, these best practices would need to take into account farmers' perspectives and contextual challenges.

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A simulation model to investigate interactions between first season grazing calves and Ostertagia ostertagi

Cited by 16 publications

References 90 publications

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

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

Feed evaluation science

A longitudinal study of gastrointestinal parasites in English dairy farms. Practices and factors associated with first lactation heifer exposure to Ostertagia ostertagi on pasture

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