A general model is proposed for predicting the effects of subclinical pathogen challenges of different doses and virulence on the relative feed intake (RFI) of animals. The RFI is defined as the feed intake (FI, kg/d) of the animal challenged by a pathogen divided by its FI in the same state had it not been challenged. Actual FI can be predicted from the RFI and the animal's state. The RFI was assumed to be affected only when animals were naïve to a particular pathogen (i.e., had not previously experienced it) and when the challenge dose was above a predetermined threshold. The model is for the period from recognition of a pathogen through acquisition and subsequent expression of immunity. The way in which RFI changes with time is described by 5 main parameters and is based on data for RFI during different pathogen challenges of a range of hosts. Lag time (L, d) is the delay from a pathogen challenge until any effects on RFI are seen. Reduction time (R, d) describes the time it takes for the lowest value of RFI (lambda) to be achieved. The duration time (D, d) describes the time that lambda is maintained for, and rho (RFI/d) describes the rate of recovery of RFI until RFI = 1. There is no compensatory intake, and RFI is always < or = 1. The effects of host resistance on the values of the model parameters are proposed. Attempts were made to parameterize the model; when data were scarce, initial parameter values were derived on conceptual grounds. Predictions of the effects of pathogen dose, virulence, and host resistance are described and discussed. When comparing the responses in RFI for different genotypes, it is crucial to define the pathogen challenge (in terms of dose and virulence) and the degree of resistance of different hosts. Possible interactions between dose, virulence, and resistance were explored. Feed intake of healthy and challenged animals, at a time, may be different once the challenged animal has recovered (RFI = 1). The issue of reductions in FI during pathogen challenges is important for nutritionist and animal breeders. The large variation that has been observed for reductions in FI during pathogen challenges may be a viable point of selection. The points highlighted will aid selection strategies by quantifying the effects of pathogen dose and virulence, and time, on the FI of challenged animals. The proposed model may be integrated with other models of growth to predict animal performance during exposure to pathogens.

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Predictive frameworks for performance under both physical and social stressors are available, but no general framework yet exists for predicting the performance of animals exposed to pathogens. The aim of this paper was to identify the key problems that would need to be solved to achieve this. Challenges of a range of hosts by a range of pathogens were reviewed to consider reductions in growth beyond those associated with reductions in voluntary food intake (VFI). Pair-feeding and marginal response studies identified the extent and mechanisms of how further reductions in growth occur beyond those caused by reduced VFI. Further reductions in growth depended on the pathogen, the host and the dose and were time dependent. In some instances the reduction in VFI fully explained the reduction in growth. Marginal response experiments showed increased maintenance requirements during exposure to pathogens, but these were different for specific amino acids. There were no clear effects on marginal efficiency. Innate immune functions, repair of damaged tissue and expression of acquired immunity caused significant but variable increases in protein (amino acid) requirements. More resistant genotypes had greater requirements for mounting immune responses. The partitioning of protein (amino acids) was found to be different during pathogen challenges. Prediction of the requirements and partitioning of amino acids between growth and immune functions appears to be a crucial problem to solve in order to predict performance during pathogen challenges of different kinds and doses. The problems of accounting for reductions in performance during pathogen challenges that are described here provide a useful starting point for future modelling and experimental solutions.Keywords: diseases, energy, growth, pathogens, protein IntroductionPredicting the effects of physical (Black et al., 1986;Wellock et al., 2003a), social (Wellock et al., 2003b and infectious (Black et al., 1999) stressors on performance is important for guiding future management, genetic selection and experimental strategies. No general model exists that predicts growth and performance of different host genotypes, when given access to different kinds of foods and challenged by pathogens. The aim of this paper was to characterise reductions in growth during exposure to different kinds and amounts of pathogen that were not caused by a reduction in voluntary food intake (Sandberg et al., 2006). This allowed for the main consequences of pathogen challenges that would need addressing in a predictive framework of growth to be identified.There is no general agreement on the overall problems that need solving in order to predict growth during pathogen challenges (Black et al., 1999; Coop and Kyriazakis, 1999;Kyriazakis, 2003;Powanda and Beisel, 2003). A general comprehensive model can provide a clearer background for the design of future experiments, and help improve our current understanding of the interactions between pathogen challenge, the host and its nutrition. To achieve t...

This article explores the role of the interactive researcher by drawing on Jürgen Habermas' theory of communicative action to develop the concept of virtual participant. An ideal interactive research project is used to explore the issues faced by interactive researchers in three phases -initial, implementation and conclusion. In each phase, an interactive research project is used to demonstrate the issues that are discussed. First, this article argues that the concept of communicative rationality can be helpful to understand how mutually trusting relationships between practitioners and researchers can be established at the beginning of a project. Second, it argues that the idea of taking a virtual stand on validity claims can be used during a project to engage a performative attitude and achieve mutual understanding with actors in the practice system. Third, this article argues that the concept of the virtual participant can explain how the interactive researcher can engage in performative action without becoming captive to the practice system. The concept of the virtual participant helps to enhance understanding of the complexity of the role of the interactive researcher.

We argue that municipal adult education (MAE) can be seen as a place for displaced and abnormal citizens to gain temporary stability, enabling their shaping into desirable subjects. Drawing on a poststructural discursive analysis, we analyze policy texts and interviews with teachers and students. Our analysis illustrates how two distinct but interrelated student subjectivities are shaped: the rootless, unmotivated, and irresponsible student; and the responsible, motivated, and goal-oriented student. The difference is that the latter of these subjectivities is positioned as desirable. MAE provides a temporary place in time, a heterotopia of deviation, allowing students to escape precarious employment. The heterotopia places the students in a positive utopian dream of the future. A utopia is not a real place, and what is to become of the students after finishing MAE is not determined; the students themselves should shape it. If they fail, in line with a neoliberal governmentality, it is their own fault.