Bertrand Dumont

Prospects from agroecology and industrial ecology for animal production in the 21st century

Agroecology and industrial ecology can be viewed as complementary means for reducing the environmental footprint of animal farming systems: agroecology mainly by stimulating natural processes to reduce inputs, and industrial ecology by closing system loops, thereby reducing demand for raw materials, lowering pollution and saving on waste treatment. Surprisingly, animal farming systems have so far been ignored in most agroecological thinking. On the basis of a study by Altieri, who identified the key ecological processes to be optimized, we propose five principles for the design of sustainable animal production systems: (i) adopting management practices aiming to improve animal health, (ii) decreasing the inputs needed for production, (iii) decreasing pollution by optimizing the metabolic functioning of farming systems, (iv) enhancing diversity within animal production systems to strengthen their resilience and (v) preserving biological diversity in agroecosystems by adapting management practices. We then discuss how these different principles combine to generate environmental, social and economic performance in six animal production systems (ruminants, pigs, rabbits and aquaculture) covering a long gradient of intensification. The two principles concerning economy of inputs and reduction of pollution emerged in nearly all the case studies, a finding that can be explained by the economic and regulatory constraints affecting animal production. Integrated management of animal health was seldom mobilized, as alternatives to chemical drugs have only recently been investigated, and the results are not yet transferable to farming practices. A number of ecological functions and ecosystem services (recycling of nutrients, forage yield, pollination, resistance to weed invasion, etc.) are closely linked to biodiversity, and their persistence depends largely on maintaining biological diversity in agroecosystems. We conclude that the development of such ecology-based alternatives for animal production implies changes in the positions adopted by technicians and extension services, researchers and policymakers. Animal production systems should not only be considered holistically, but also in the diversity of their local and regional conditions. The ability of farmers to make their own decisions on the basis of the close monitoring of system performance is most important to ensure system sustainability.

Grazing behaviour of sheep in a situation of conflict between feeding and social motivations.

We investigated how food preferences and social bonds interact to determine the choice of grazing location in sheep. Ewes of INRA 401 breed were grazed in plots in which taller areas, i.e. preferred feeding sites, were left to grow at 15 or 50 m from a socially attractive site, i.e. familiar ewes placed in a public pen at one end of the plot. Eight experimental ewes were tested either alone or in groups with one, three or six accompanying animals chosen amongst 20 other familiar ewes. We used a Latin square design, in which the eight treatments (two distancesxfour group sizes) were balanced in 8 measurement days. We recorded, in 20-min tests, the behaviour of the experimental ewes by focal sampling, and the location of each animal in the groups by scan sampling. Foraging location, dietary choices and vigilance behaviour of ewes were affected by both the distance between the group of public peers and the preferred feeding site, and the size of their own group. Our results suggest that a sheep will move whether alone or with a few peers to a preferred feeding site located close to the core of its social group. In a small sub-group, its frequency of vigilance behaviour increases, probably to maintain social contact with the rest of the group. Conversely, a sheep will not leave its group to reach a preferred feeding site located further away unless it is followed by several other peers.

Multi-agent simulation of group foraging in sheep: effects of spatial memory, conspecific attraction and plot size

We describe the modelling of sheep spatial memory at pasture using an individual-based approach. As our modelling goal requires specification of stochastic and state-dependent random movements and some social aspects, we used a multi-agent system that can be regarded as a special case of an individual-based model (IBM). We used a three-phase approach to implement the synchronization kernel since this is particularly well adapted to spatial resource competition. One of the main differences between this model and most earlier IBMs is that we were able to use real field data from animal experiments for model validation. We thus compared real system behaviour with model predictions. As the simulation results were consistent with field data, we used the model as an extrapolation tool to investigate conditions that had not been tested, or that are not easily amenable to experimentation. This enabled us to show that conspecific attraction can have disruptive effects on the searching efficiency of foragers in habitats, where patches deplete rapidly. We also show that the advantages of a good spatial memory vary according to the size of the environment to be explored.

Decision making in group departures of sheep is a continuous process

For coordinated movement, group-living individuals have to reach consensus decisions through recruitment processes. Success in recruitment can depend on the spatial distribution and behaviour of animals before and/or after departure, and on their affinitive relationships. We tested the effect of such factors on recruitment processes in a group of 19 ewe lambs, Ovis aries, at pasture. Two observers continuously videotaped the behaviours of animals from a platform located in the centre of the field. Results showed that group orientation, group vigilance and activities such as head movements, stillness and number of steps increased before departure. Using general linear modelling we found that changes in most of these variables predicted the number of participants in movements. Similarly, activity of the first mover was modified in the last 2 min preceding departure, and at departure time the location and number of close neighbours of the first mover were especially influential in recruiting conspecifics. Animals first recruited were those that were close to the first mover and also its preferential partners. The behaviours of the second and third moving individuals could further influence the recruitment process. Moreover, there were clues that individuals were able to recruit others intentionally. Our findings emphasize that decision making in a group of domestic sheep was a continuous and distributed process. Recruitment depended both on group state and on the behaviour of individuals and their social relationships.

Choice of sheep and cattle between vegetative and reproductive cocksfoot patches

Unexploited reproductive areas appear in pastures when grazing pressure is low. This study was made to determine how sward height in vegetative patches and fasting influence the ability of sheep and cattle to feed on these areas of low quality but highly available forage. Preference and rate of biting of 1-year-old ewes and 18-month-old heifers were recorded during 30 min tests on plots half vegetative and half reproductive in area, with vegetative swards at 7, 11 or 18 cm. Plots were grazed by unfasted animals or after a fast of 16 or 24 h. Heifers spent more time grazing on reproductive swards than ewes (49% vs. 34%; P < 0.01), but there were wide variations between individuals within each species. Individual animals which had the higher rate of biting on vegetative patches generally grazed them longer. The time spent grazing on vegetative patches increased with sward height in both species. It was 20%, 47% and 74% in heifers (P < 0.001) and 43%, 63% and 87% in ewes (P < 0.001) for treatments T7, T11 and T18, respectively. There was no interaction between species and sward height. The time spent grazing on vegetative patches decreased with fasting in ewes (P < 0.05) but not in heifers. The rate of biting on vegetative swards gradually increased with fasting in heifers, whereas in ewes there was a decrease after 16 h of fasting.

Response of foraging sheep to variability in the spatial distribution of resources

In stable and predictable environments, grazing herbivores can use spatial memory to increase foraging efficiency. As most natural systems are characterized by unpredictability in the distribution of resources, we explored the foraging efficiency of sheep, Ovis aries, in relation to variability in spatial distribution of resources, predicting that as the environment became more variable, spatial memory would be replaced by sampling behaviour. We manipulated resource distribution by using bowls of food pellets to create seven preferred resource sites within a grass pasture. The provisioning of the bowls with pellets and the mass of pellets therein were altered to create four treatments in which resources remained stable or varied within and between resource sites. Where bowl position was predictable, sheep showed increased foraging efficiency by reducing the time devoted to pellet foraging in relation to the total mass of pellets consumed and by visiting fewer empty bowls while searching within a site. Where bowl position became less predictable, sheep increased sampling within sites, visiting more empty bowls before leaving a site. However, in contrast with previous observations, sheep did not return preferentially to the highest-quality sites within the test plot. This study suggests that sheep could use spatial memory at small spatial scales to improve foraging efficiency where resource distribution is predictable. The ability to switch between foraging tactics may allow sheep to maintain foraging success under variable conditions.

Selection for nutrients by red deer hinds feeding on a mixed forest edge

We studied the nutritional behaviour of hinds foraging on a mixed-forest edge by direct observation of their choices at each season and by measuring nutrient concentration in the plants. We compared nutrient concentrations in the observed diets with those in the total available vegetation, and with those of 1,000 randomly simulated diets in which we included only those plants that were actually eaten by the animal. Whether the available or the consumed feeds were used as the basis for comparisons had important consequences due to the presence of conifers and ferns, which were high in soluble sugars but were never eaten by the animals (potentially due to their toxicity). The selected diets were lower in sugars than the total available vegetation in summer, but were actually higher in sugars than the random diets generated from consumed forage species only. Hind diets contained more soluble sugars but not more protein than simulated diets in all seasons. Contrary to our prediction, anti-nutritional compounds (ADL and tannins) were avoided only in winter. Compared to simulated diets, hinds consumed more tannins in spring and summer and more ADL in summer and autumn. We suggest that this was a consequence of selection for soluble sugars, because the preferred plant species, which had high soluble sugar concentrations, also contained a large proportion of the anti-nutritional compounds eaten. In winter, the grass-dominated diets contained more fibre (NDF) and less ADL than the simulated diets, indicating that hinds orient their feeding towards digestible fibres. The switch from a browser to a grazer diet was related to a change in the availability of the nutrients, mainly soluble sugars. In our study, grasses contained more soluble sugars and proteins than deciduous browse during winter. This calls into question the dichotomy usually assumed in the literature between grass and browse in terms of nutrient content.

Plant trait–digestibility relationships across management and climate gradients in permanent grasslands

1. Dry matter digestibility is a critical component of herbage nutritive value, a major service delivered by grasslands. The aim of this study was to test whether the dominance hypothesis applies to assess the impacts of environmental gradients and management regimes on thiscomponent of herbage nutritive value in permanent grasslands. 2. At the plant level, digestibility has been related to a number of functional traits, but whether this can be scaled up to the community level in species-rich grasslands and how such relationships are modulated by environmental conditions and management regimes remainunknown. Our primary objective was to test whether community-weighted means – species trait values weighted by the species abundance – of morphological, phenological and chemical traits could be used to explain variations in digestibility over a large range of climatic contexts,soil resource levels and management regimes. Our second objective was to explain variations in community digestibility within and among nine contrasting sites along large natural and man-induced environmental gradients.3. Over the whole data set, digestibility and most community-weighted means of traits responded to climatic factors and management regimes, but relations were not always significant when each site was considered separately. Community digestibility was significantly related to one or more plant traits within each site and to all of the measured traits when considering all the sites. Leaf dry matter content (LDMC) had the most consistent effects on digestibility, with a strikingly similar negative effect within each site. Potential evapotranspiration was negatively related to digestibility and contributed to explain a large part of the among-site variance. In addition, a low return interval of disturbance and a high disturbance intensity (biomass removal) were both associated with a high digestibility.4. Synthesis and applications. Disturbance regime, plant traits and local climate impacted dry matter digestibility roughly equally in grasslands. The effects of community composition on digestibility and its response to abiotic factors could be successfully captured by community weightedmeans of leaf dry matter content. This functional marker can be used to develop indicators and grassland management rules to support farmers in the refinement of their practices towards specific needs, such as target production outputs.

Generalization of conditioned food aversions in grazing sheep and its implications for food categorization

When grazing on heterogeneous pastures, herbivores may rely on food item generalization and categorization processes for reducing information processing while selecting their diet. The objective of this study was to assess the generalization of an aversion by grazing sheep for items differing by one or two criteria from an item against which they were negatively conditioned. Four items cultivated in pots were offered to the animals, resulting from the combination of an intrinsic criterion, i.e. grass species (ryegrass and fescue) and a transitory criterion, i.e. sward height (tall and short). We assessed the generalization process by comparing binary choices between the initially preferred tall ryegrass and the three other items, before and after animals had been partially conditioned against tall ryegrass. This method proved useful in assessing the generalization of an aversion. Sheep did not generalize their aversion on the basis of sward height but rather on species: they increased their preference for tall fescue and decreased their instantaneous preference for short ryegrass after having been conditioned against tall ryegrass. The generalization of an aversion through different states of a same species could indicate the possibility of a species-based categorization by grazing herbivores.

Forty research issues for the redesign of animal production systems in the 21st century

Agroecology offers a scientific and operational framework for redesigning animal production systems (APS) so that they better cope with the coming challenges. Grounded in the stimulation and valorization of natural processes to reduce inputs and pollutions in agroecosystems, it opens a challenging research agenda for the animal science community. In this paper, we identify key research issues that define this agenda. We first stress the need to assess animal robustness by measurable traits, to analyze trade-offs between production and adaptation traits at within-breed and between-breed level, and to better understand how group selection, epigenetics and animal learning shape performance. Second, we propose research on the nutritive value of alternative feed resources, including the environmental impacts of producing these resources and their associated non-provisioning services. Third, we look at how the design of APS based on agroecological principles valorizes interactions between system components and promotes biological diversity at multiple scales to increase system resilience. Addressing such challenges requires a collection of theories and models (concept-knowledge theory, viability theory, companion modeling, etc.). Acknowledging the ecology of contexts and analyzing the rationales behind traditional small-scale systems will increase our understanding of mechanisms contributing to the success or failure of agroecological practices and systems. Fourth, the large-scale development of agroecological products will require analysis of resistance to change among farmers and other actors in the food chain. Certifications and market-based incentives could be an important lever for the expansion of agroecological alternatives in APS. Finally, we question the suitability of current agriculture extension services and public funding mechanisms for scaling-up agroecological practices and systems.