How plant traits respond to and affect vertebrate and invertebrate herbivores-Are measurements comparable across herbivore types?

Despite plants realistically being affected by vertebrate and invertebrate herbivores simultaneously, fundamental differences in the ecology and evolution of these two herbivore guilds often means their impacts on plants are studied separately. A synthesis of the literature is needed to understand the types of plant traits examined and their response to, and effect on (in terms of forage selection) vertebrate and invertebrate herbivory, and to identify associated knowledge gaps. Focusing on grassland systems and species, we found 138 articles that met our criteria: 39 invertebrate, 97 vertebrate and 2 focussed on both vertebrate and invertebrate herbivores. Our study identified invertebrate focussed research, research conducted in the Southern Hemisphere and research on nondomesticated herbivores was significantly underrepresented based on our search and should be a focus of future research. Differences in study focus (trait response or trait effect), along with differences in the types of traits examined, led to limited opportunity for comparison between the two herbivore guilds. This review therefore predominantly discusses the response and effect of plant traits to each herbivore guild separately. In future studies, we suggest this review be used as a guide for trait selection, to improve comparability and the broader significance of results.

Understanding Animal-Plant-Parasite Interactions to Improve the Management of Gastrointestinal Nematodes in Grazing Ruminants

Grazing systems have great potential to promote animal welfare by allowing animals to express natural behaviours, but they also present risks to the animals. Diseases caused by gastrointestinal nematodes are some of the most important causes of poor ruminant health and welfare in grazing systems and cause important economic losses. Reduced growth, health, reproduction and fitness, and negative affective states that indicate suffering are some of the negative effects on welfare in animals infected by gastrointestinal nematode parasitism. Conventional forms of control are based on anthelmintics, but their growing inefficiency due to resistance to many drugs, their potential for contamination of soil and products, and negative public opinion indicate an urgency to seek alternatives. We can learn to deal with these challenges by observing biological aspects of the parasite and the host’s behaviour to develop managements that have a multidimensional view that vary in time and space. Improving animal welfare in the context of the parasitic challenge in grazing systems should be seen as a priority to ensure the sustainability of livestock production. Among the measures to control gastrointestinal nematodes and increase animal welfare in grazing systems are the management and decontamination of pastures, offering multispecies pastures, and grazing strategies such as co-grazing with other species that have different grazing behaviours, rotational grazing with short grazing periods, and improved nutrition. Genetic selection to improve herd or flock parasite resistance to gastrointestinal nematode infection may also be incorporated into a holistic control plan, aiming at a substantial reduction in the use of anthelmintics and endectocides to make grazing systems more sustainable.

Bioactivity of plants eaten by wild birds against laboratory models of parasites and pathogens

Plants are not only used as energy and nutrient resources for herbivores. Plants can be ingested because of their activity against host parasites and other pathogens. This so-called medicinal role of plants is well reported in ethnopharmacology and under-reported in wild animals. More studies on wild animals are needed because any plant in the world contains bioactive compounds, and probably all plants, no matter how toxic they are, experience herbivory. For example, we tested the activity of extracts and essential oils from Papaver rhoeas and Echium plantagineum against a selection of laboratory pathogens because Great bustards Otis tarda preferred these plants during the mating season, with male fecal droppings showing a higher frequency of P. rhoeas particles than the fecal droppings of females. We hypothesized that P. rhoeas could be helpful for males in the mating season if any part of this plant harbors bioactivity against parasites and other pathogens. Males’ immune system is weakened during the mating season because of their investment in secondary sexual characters and sexual display. As a first exploration of the bioactivity of these plants, we evaluated extracts of both plants against a sample of laboratory models, including a flagellated protozoon (Trichomonas gallinae), a nematode (Meloidogyne javanica) and a fungus (Aspergillus niger). Non-polar and polar extracts of the aerial parts of P. rhoeas, especially the extracts of flowers and capsules, and the extracts of leaves and flowers of E. plantagineum showed activity against nematodes and trichomonads. The bioactivity of plants against parasites could explain the foraging behavior of stressed animals. The chemical communication underpinning the capacity of fauna to recognize those plants is far less known.

Immunoecology of Species with Alternative Reproductive Tactics and Strategies

Alternative reproductive tactics and strategies (ARTS) refer to polymorphic reproductive behaviours in which in addition to the usual two sexes, there are one or more alternative morphs, usually male, that have evolved the ability to circumvent direct intra-sexual competition. Each morph has its own morphological, ecological, developmental, behavioural, life-history, and physiological profile that shifts the balance between reproduction and self-maintenance, one aspect being immunity. Immunoecological work on species with ARTS, which is the topic of this review, is particularly interesting because the alternative morphs make it possible to separate the effects of sex per se from other factors that in other species are inextricably linked with sex. We first summarize the evolution, development, and maintenance of ARTS. We then review immunoecological hypotheses relevant to species with ARTS, dividing them into physiological, life-history, and ecological hypotheses. In context of these hypotheses, we critically review in detail all immunoecological studies we could find on species with ARTS. Several interesting patterns emerge. Oddly, there is a paucity of studies on insects, despite the many benefits that arise from working with insects: larger sample sizes, simple immune systems, and countless forms of alternative reproductive strategies and tactics. Of all the hypotheses considered, the immunocompetence handicap hypothesis has generated the greatest amount of work, but not necessarily the greatest level of understanding. Unfortunately, it is often used as a general guiding principle rather than a source of explicitly articulated predictions. Other hypotheses are usually considered a posteriori, but perhaps they should take centre stage. Whereas blanket concepts such as “immunocompetence” and “androgens” might be useful to develop a rationale, predictions need to be far more explicitly articulated. Integration so far has been a one-way street, with ecologists delving deeper into physiology, sometimes at the cost of ignoring their organisms’ evolutionary history and ecology. One possible useful framework is to divide ecological and evolutionary factors affecting immunity into those that stimulate the immune system, and those that depress it. Finally, the contributions of genomics to ecology are being increasingly recognized and sometimes applied to species with ARTS, but we must ensure that evolutionary and ecological hypotheses drive the effort, as there is no grandeur in the strict reductionist view of life.

Voisin Rational Grazing as a Sustainable Alternative for Livestock Production

Current livestock practices do not meet current real-world social and environmental requirements, pushing farmers away from rural areas and only sustaining high productivity through the overuse of fossil fuels, causing numerous environmental side effects. In this narrative review, we explore how the Voisin Rational Grazing (VRG) system responds to this problem. VRG is an agroecological system based on four principles that maximise pasture growth and ruminant intake, while, at the same time, maintaining system sustainability. It applies a wide range of regenerative agricultural practices, such as the use of multispecies swards combined with agroforestry. Planning allows grazing to take place when pastures reach their optimal resting period, thus promoting vigorous pasture regrowth. Moreover, paddocks are designed in a way that allow animals to have free access to water and shade, improving overall animal welfare. In combination, these practices result in increased soil C uptake and soil health, boost water retention, and protect water quality. VRG may be used to provide ecosystem services that mitigate some of the current global challenges and create opportunities for farmers to apply greener practices and become more resilient. It can be said that VRG practitioners are part of the initiatives that are rethinking modern livestock agriculture. Its main challenges, however, arise from social constraints. More specifically, local incentives and initiatives that encourage farmers to take an interest in the ecological processes involved in livestock farming are still lacking. Little research has been conducted to validate the empirical evidence of VRG benefits on animal performance or to overcome VRG limitations.

Can Lambs in Pain Identify Medicated Feed?

Lambs in Australia undergo painful husbandry procedures as part of common husbandry. The magnitude and duration of pain are difficult to assess in lambs. Most currently used methods rely on behavioral expressions and physiological markers that may fail to detect the state of pain an animal experience. This study examined motivation of 12-week-old lambs experiencing chronic pain to self-medicate by consumption of feed containing an analgesic agent as an indicator of pain in lambs. In this study, 36 male Merino lambs were individually penned and acclimated to pelleted feed and two artificial odors: strawberry and banana. Once acclimated to odored feed, lambs were tested for their individual preference for the odors. Lambs were then assigned to one of two groups: Sham—sham handled day 0 and 7 or Ring—Ring castrated day 0 and tail docked day 7. To enable self-medication testing, lambs underwent a conditioning period (day 0–3) followed by the self-medication period (day 7–12). On day 0 lambs were castrated or sham handled, and then offered only medicated feed that contained an odor cue (either strawberry or banana). On day 7, lambs underwent tail-docking or sham handling and were offered both the conditioned medicated feed and non-medicated feed. Amount of each feed consumed was recorded 1 and 12 h after offer each day. Blood samples were taken for cortisol and white blood cell analysis and behavioral observations were recorded for 12 h following treatment. There was no difference in preference for medicated feed between Ring and Sham lambs during the self-medication phase (P = 0.18). Lambs in both groups displayed a significant preference for strawberry cued medicated feed during the self-medicated period when compared to the other testing periods (P = 0.05). Ring lambs displayed more active pain behaviors (mean = 15.1) than Sham (mean = 0.4, P < 0.05). Following castration, Ring lambs had a higher neutrophil/lymphocyte ratio at 6, 24, 48, and 72 h. This study was not able to demonstrate that lambs can self-medicate for a state of pain.

Animal Design Through Functional Dietary Diversity for Future Productive Landscapes

Pastoral livestock production systems are facing considerable societal pressure to reduce environmental impact, enhance animal welfare, and promote product integrity, while maintaining or increasing system profitability. Design theory is the conscious tailoring of a system for a specific or set of purposes. Then, animals—as biological systems nested in grazing environments—can be designed in order to achieve multi-faceted goals. We argue that phytochemical rich diets through dietary taxonomical diversity can be used as a design tool for both current animal product integrity and to develop future multipurpose animals. Through conscious choice, animals offered a diverse array of plants tailor a diet, which better meets their individual requirements for nutrients, pharmaceuticals, and prophylactics. Phytochemical rich diets with diverse arrangements of plant secondary compounds also reduce environmental impacts of grazing animals by manipulating the use of C and N, thereby reducing methane production and excretion of N. Subsequently functional dietary diversity (FDD), as opposed to dietary monotony, offers better nourishment, health benefits and hedonic value (positive reward increasing “liking” of feed), as well as the opportunity for individualism; and thereby eudaimonic well-being. Moreover, phytochemical rich diets with diverse arrangements of plant secondary compounds may translate in animal products with similar richness, enhancing consumer human health and well-being. Functional dietary diversity also allows us to design future animals. Dietary exposure begins in utero, continues through mothers' milk, and carries on in early-life experiences, influencing dietary preferences later in life. More specifically, in utero exposure to specific flavors cause epigenetic changes that alter morphological and physiological mechanisms that influence future “wanting,” “liking” and learning of particular foods and foodscapes. In this context, we argue that in utero and early life exposure to designed flavors of future multifunctional foodscapes allow us to graze future ruminants with enhanced multiple ecosystem services. Collectively, the strategic use of FDD allows us to “create” animals and their products for immediate and future food, health, and wealth. Finally, implementing design theory provides a link between our thoughtscape (i.e., the use of FDD as design) to future landscapes, which provides a beneficial foodscape to the animals, an subsequently to us.

Influence of tropical upright pasture structural and chemical characteristics on lamb grazing time

Tropical pasture canopy characteristics can alter lamb ingestive behavior. Our study evaluated the ingestive behavior of young lambs in different tropical pastures to identify which variables interfere in their grazing activity. Two years of study were carried out with 54 weaned lambs distributed in three different pasture canopies: 1) monoculture of an upright grass, guinea grass (Panicum maximum; GG); 2) monoculture of a shrubby legume pigeon pea (Cajanus cajan; PP) and 3) contiguous paddock with half GG and half PP (GP). The experiment was set out in a randomized complete block design (3 blocks). Lamb ingestive behavior was observed from sunrise to sunset with records every 5 minutes. To identify the main variables that affected lamb grazing activity, a multivariate analysis of the Decision Tree was performed. Our results showed that there was no difference in the ingestive behavior parameters of young lambs in different canopies (P > 0.05). There was interaction among the canopies and the experimental periods for the variables idleness time and biting rate (P ≤ 0.05). Lambs in all canopies showed more idleness time in the first evaluation period. Lambs in canopies containing grass (GG and GP) exhibited greater bites per minute throughout the experimental period. Lamb grazing time increased 40% as experimental period progressed and plants matured. The Decision Tree identified leaf:stem ratio as the variable that most influenced lamb grazing time in GG and GP canopies while in the PP, grazing time was directly related to canopy height. The behavior of young lambs on tropical pasture is variable as there is a change in the behavioral response to canopy characteristics over time. In addition, the grazing time of these animals can be estimated by means of variables related to canopy structural characteristics (leaf:stem ratio and height) together with chemical variables.

Intake, digestibility, and milk yield response in dairy buffaloes fed Panicum maximum cv. Mombasa supplemented with seeds of tropical açai palm

The use of alternative tropical feeds, such as açai seeds, under tropical pasture production systems, may help to optimize buffalo milk production mainly in the Amazon region, which has the largest worldwide açai production. This study evaluated the effects of dietary inclusion of açai palm seeds in the supplement on nutrient utilization and milk yield response of lactating buffaloes grazing Panicum maximum cv. Mombasa. The treatments comprised four levels of açai palm seeds (0, 198.4, 396.8, and 595.2 g/kg of dry matter) and a treatment without concentrate supplementation (WCS). Five half-breed Murrah female buffaloes with average body weight ± (SEM) of 577 ± (20.4) kg were used in a 5 × 5 Latin square design. There was no effect of the inclusion of açai palm seeds on the total dry matter and nutrient intakes (P>0.05). The digestibility of dry matter, organic matter, neutral detergent fiber, and total digestible nutrients showed a linear decreasing pattern (P<0.05), whereas the digestibility of crude protein demonstrated a quadratic pattern, as açai palm seed inclusion level increased (P<0.05). Milk production demonstrated a quadratic pattern as açai palm seed inclusion increased (P<0.05). There was no effect of açai palm seed inclusion on milk composition (P>0.05), except for fat (%), protein (%), and the concentration of total dry extract (P<0.05). There was no difference in nutrient intake and digestibility and milk performance, between supplemented and WCS animals (P>0.05). In conclusion, the inclusion of açai palm seeds at 198.4 g/kg DM in the supplement of grazing buffaloes improves the digestibility of crude protein and milk production, without detrimental effects on nutrient intake. Also, açai palm seeds may be a potential replacer of Panicum maximum cv. Mombasa under tropical conditions.

Drug instrumentalization

Psychoactive drugs with addiction potential are widely used by people of virtually all cultures in a non-addictive way. In order to understand this behaviour, its population penetrance, and its persistence, drug instrumentalization was suggested as a driving force for this consumption. Drug instrumentalization theory holds that psychoactive drugs are consumed in a very systematic way in order to make other, non-drug-related behaviours more efficient. Here, we review the evolutionary origin of this behaviour and its psychological mechanisms and explore the neurobiological and neuropharmacological mechanisms underlying them. Instrumentalization goals are discussed, for which an environmentally selective and mental state-dependent consumption of psychoactive drugs can be learned and maintained in a non-addictive way. A small percentage of people who regularly instrumentalize psychoactive drugs make a transition to addiction, which often starts with qualitative and quantitative changes in the instrumentalization goals. As such, addiction is proposed to develop from previously established long-term drug instrumentalization. Thus, preventing and treating drug addiction in an individualized medicine approach may essentially require understanding and supporting personal instrumentalization goals.

Diet selection and trade-offs between condensed tannins and nutrients in parasitized sheep

Foraging behavior by parasitized herbivores can be interpreted as a decision-making process where individuals are faced with trading-off the ingestion of nutrients with the ingestion of potentially medicinal -and toxic- plant secondary compounds. We determined how parasitized sheep prioritize selection of crude protein, energy and a medicinal plant secondary compound (quebracho tannins-QT). Foraging preferences were tested in 40 lambs before experiencing a parasitic infection (Phase 1), during an infection (Phase 2; 10,000 L₃Haemonchus contortus per lamb) and after chemotherapy (Phase 3). Lambs were assigned to four groups (10 lambs/group) such that animals in Group 1 (Control) could choose between foods of high (HEP) or low (LEP) energy to protein ratios. The other groups received the same choice, but QT were added (4%) to HEP (Group 2), to LEP (Group 3) or to both foods (Group 4). All groups under a parasitic infection (Phase 2) increased their preference for HEP (from 0.44 to 0.66 ± 0.042; P < 0.05) and intake of digestible energy (from 0.106 to 0.126 ± 0.007 Mcal/kg BW; P < 0.05) relative to Phase 1, a pattern that remained during Phase 3. Only lambs receiving QT in HEP increased their intake of QT from Phase 1 to Phase 2 (P < 0.05). Fecal egg counts and blood parameters revealed a parasitic infection (P < 0.05) in Phase 2 that subsided in Phase 3, although no differences were detected among groups (P > 0.05). The importance of protein nutrition on parasitized animals has been highlighted before, but these results suggest that lambs prioritized the ingestion of energy-dense over protein-dense foods or medicinal condensed tannins when challenged by gastrointestinal parasitism. Consumption of medicinal tannins represented a side-effect of the preference manifested for energy-dense foods during testing.

Effects of grazing birdsfoot trefoil-enriched pasture on managing Haemonchus contortus infection in Suffolk crossbred lambs

High-tannin forages can be used to help mitigate the serious limitations associated with gastrointestinal nematode (GIN) infections on efficient small ruminant production. The objective of this experiment was to determine how grazing a GIN-free, established stand of a high-tannin cultivar of birdsfoot trefoil (Lotus corniculatus L.) influenced the prevention or treatment of Haemonchus contortus (Hc) infection in lambs. A birdsfoot trefoil-enriched pasture was established on an area that was previously row cropped and not grazed for at least 15 yr. Treatments included preventative (PREV) with parasite-naïve lambs transitioned onto pasture 1 wk prior to receiving an infection of 10,000 Hc larvae, therapy (THER) with parasite-naïve lambs infected with 10,000 Hc larvae 4 wk prior to the start of grazing, and control (CONT) with naïve, uninfected lambs to verify that natural infection did not occur on pasture. Each treatment group of 12 Suffolk crossbred lambs was divided into 3 replicates per treatment, and all were supplemented with a grain mix to provide 16% CP. Fecal egg count (FEC, eggs/g wet feces) in THER lambs peaked 1 wk after the start of grazing (9,404) and after 4 wk fell to 1,068, equivalent to a FEC reduction of 88.6%. Lambs in PREV had a peak FEC of 4872 at 4 wk after infection where peak FEC was 48% less in PREV than THER lambs. Lambs in CONT did not have measurable FEC for the duration of this study. Packed cell volume (PCV, %) reflected infection status of the lambs in each group, where CONT (32%) had the highest (P < 0.05) PCV followed by THER (29%) and PREV (26%). Total weight gained in CONT lambs was greatest at 5.51 kg (P < 0.01), whereas THER and PREV (2.68 and 2.97 kg, respectively) did not differ. Grazing birdsfoot trefoil-enriched pasture can have both therapeutic and preventative effects on Hc infection in lambs and can be used in a systems approach to control GIN parasites in grazing sheep.

Gastrointestinal nematode infection and feeding behaviour of goats in a heterogeneous vegetation: No evidence of therapeutic self-medication

The aim of this study was to identify modifications in the feeding behaviour of goats browsing a tropical deciduous forest (TDF) when natural gastrointestinal nematode (GIN) infection was suppressed. Continuous bite monitoring through direct observation was implemented in 12 Criollo goats (adults, non-pregnant) foraging for 4 h per day during the rainy season. In the first Period (P1, one observation point) all goats were maintained with natural GIN infection. In the second Period (P2, three observation points), goats were equally distributed into 2 groups: i) moxidectin treated group (TG) used in a suppressive scheme; and ii) naturally infected group (IG). For each observation point, goats were monitored at three timepoints per day (80 min each), for three consecutive days, to estimate their intake of dry matter (DM), condensed tannins (CT), crude protein, metabolizable energy and digestible DM. Live weight (LW), faecal samples and blood samples were obtained every 28 days to determine LW change, faecal egg counts (FEC) and packed cell volume (PCV). During P1 and P2, the TG and IG had similar LW change and PCV. During both periods, the intake of DM, CT and all macronutrients were similar for TG and IG. The suppression of GIN infection did not modify the feeding behaviour of goats. Therefore, a therapeutic self-medicative behaviour was not identified in Criollo goats browsing a TDF.

In vitro anthelmintic activity of grape pomace extract against gastrointestinal nematodes of naturally infected sheep

Grape pomace obtained as a byproduct of industrial processing of grapes retains nutrients and substances with anthelmintic potential such as saponins, tannins, and flavonoids. Therefore, this study evaluated the in vitro ovicidal and larvicidal activity of hydroalcoholic grape pomace extract against gastrointestinal nematodes of sheep. The anthelmintic evaluation was performed by in vitro assays with eggs and larvae of nematodes obtained from naturally infected donor sheep. The grape pomace extract showed high in vitro ovicidal and larvicidal activity with LD50 values of 0.30 mg/mL for egg hatching inhibition, 1.01 mg/mL for larval development inhibition and 100% efficacy in larval migration inhibition assays at all concentrations evaluated. The effect of tannins was evaluated by the addition of 50 mg/mL polyvinyl polypyrrolidone to grape pomace extract at the concentration of 12.5 mg/mL. The in vitro ovicidal activity of grape pomace was reduced by only 15% after polyvinyl polypyrrolidone addition, indicating that other phytochemicals also contribute to the ovicidal activity displayed by the extract. Our results demonstrate that grape pomace exhibits in vitro anthelmintic activity, suggesting that, beyond its nutritional potential, this pomace can also be an ally for gastrointestinal nematode control in sheep.

Use of Unpalatable Forages by Ruminants: The Influence of Experience with the Biophysical and Social Environment

Unpalatable forage resources (low nutrient density, potentially toxic metabolites) are widespread and represent a challenge for ruminant nutrition, health, and welfare. Our objective was to synthesize the role of biophysical and social experience on the use of unpalatable forages by ruminants, and highlight derived behavioural solutions for the well-being of soils, plants, and animals. Environmental experiences early in life modulate gene expression and promote learning, which alters morpho-physiological and psychological mechanisms that modify behavioural responses and change food and habitat selection. In this process, ruminants can become better adapted to the habitat where they are reared. Moreover, experiential learning provides flexibility in diet selection, which is critical for changing foraging environments. Learned associations between unpalatable and palatable foods, if ingested in appropriate amounts, sequence, and close temporal association, induce the development of preference for the former type of food. In this way, a more uniform use of resources can be achieved from the landscape level down to the individual plant, with the associated benefits to ecosystem integrity and stability. Ruminants can also learn the medicinal benefits of ingesting foods with toxins (e.g., condensed tannins and saponins with antiparasitic properties). This knowledge on behavioural processes can be translated into behavioural applications that provide low-cost solutions to many challenges that producers face in managing sustainable livestock production systems.

Agroforestry for ruminants: a review of trees and shrubs as fodder in silvopastoral temperate and tropical production systems

Among the oldest agroforestry systems, silvopastoralism uses shrubs and trees to feed ruminants. The practice is common in extensive livestock production systems, whereas the intensification of grass-based systems in the past century has led to the removal of woody species from agricultural temperate landscapes. In Europe however, woody species are promoted again on grasslands through environment-friendly policies due to the ecosystem services they provide such as carbon sequestration, control of soil erosion, limitation of airborne pollutants and biodiversity conservation. Positive effects of browse on rumen digestion and parasite control have also been documented across different plant species and regions. Under optimal conditions, feeding ruminants from woody fodder sustains animal production. Nonetheless, limitations can restrict the use of woody forage into animal diets, such as the presence of anti-nutritive and toxic compounds. The incorporation of this resource in ruminant feeding systems raises the question of the management of the interface between the plant and the animal. Various management systems are practiced. Temperate species such as Salix spp. and Populus spp. are fed to sheep and cattle in fodder blocks or by pruning trees in New Zealand, and Fraxinus spp. or Corylus avellana in hedgerows supply forage to livestock in Belgium, whereas Leucaena leucocepahala and Desmanthus spp. browsing is common in Australia. Nowadays, ensiling and pelleting techniques are being developed as a way to store browse forage. As the renewed interest in using shrubs and trees to feed ruminants is recent, especially in temperate regions, additional research about the optimal introduction of this resource within systems is needed.

Feed resource selection of Criollo goats artificially infected with Haemonchus contortus: nutritional wisdom and prophylactic self-medication

Previous cafeteria studies suggested that a moderate natural gastrointestinal nematode (GIN) infection did not modify the resource selection of adult Criollo goats towards tannin-rich plants compared with worm-free goats. A higher infection with Haemonchus contortus could trigger a change in the resource selection behaviour towards tannin-rich foliage. Alternatively, goats might select plant species solely to meet their nutritional requirements. A cafeteria study investigated the effect of a high artificial infection with H. contortus on the feed resource selection of goats. Adult Criollo goats (37.5±4.8 kg BW) with browsing experience were distributed in two groups: the infected group (IG) with six animals artificially infected with H. contortus (6000 L3/animal); and the non-infected group (NIG) with six animals maintained worm-free. The experiment included two 5-day periods with additional 5-day adaptation period. In the first period, animals were offered foliage of five plant species with a decreasing gradient of condensed tannins (CT) (Mimosa bahamensis, Gymnopodium floribundum, Havardia albicans, Acacia pennatula, Lysiloma latisiliqum), and three plant species with negligible CT content (Leucaena leucocephala, Piscidia piscipula and Brosimum alicastrum). In the second period the foliage of B. alicastrum was withdrawn. A grain-based concentrate feed was offered daily at 1% BW in DM basis. Dry matter and nutrient intake was determined. Foliage selection of each experimental group was determined using the Chesson selection index. The H. contortus egg count per gram of faeces (EPG) was determined for infected goats twice daily. Chesson index showed a similar pattern of foliage selection on periods 1 and 2. Mean EPG of goats in IG was 2028±259 EPG during period 1 and 1 293±198 EPG during period 2 (P>0.05). During period 1, the selection pattern was highest for B. alicastrum (tannin-free), followed by a tannin-rich plant (M. bahamensis). These two plants remained as highly selected during period 2. The Chesson index showed that both experimental groups (IG and NIG) selected the same plant species in both periods. Thus, a high H. contortus infection did not affect selection of goats fed with CT-rich plants. Apparently, goats balanced their nutrient intake with the plants selected, showing evidence of nutritional wisdom. This balance may have helped to prevent excess protein in the diet and also to maintain a low GIN infection, both considered as examples of prophylactic self-medication.

Gastrointestinal nematode infection does not affect selection of tropical foliage by goats in a cafeteria trial

It is important to determine whether gastrointestinal nematodes (GINs) affect foliage choice of goats leading to confirm the expression of a self-medication behavior. This study investigated the effect of GIN infection on tropical foliage selection by goats. During experimental stage 1 (10 days), goats had a natural mixed GIN infection, and at stage 2 (10 days), goats were treated with effective anthelmintics to maintain them free of GIN infection. During stage 1 the twelve adult goats (32 ± 2.3 kg live weight [LW]) were assigned to three groups (n = 4) according to their initial GIN infection status: HI group, with fecal egg count (FEC) between 1450 and 2150 eggs per g/feces (EPG); MI group, medium FEC (592-1167 EPG); and the NI group, free from GIN infection. Fresh foliage of four tropical plants were offered to goats ad libitum for 1 h daily: Gymnopodium floribundum (high condensed tannin [CT] content, 37-40 %), Mimosa bahamensis (medium CT content, 16-17 %), Leucaena leucocephala (low CT content, 3-5 %), and Viguiera dentata (negligible CT content, 0.6-0.9 %). Jacobs' selection indexes (JSIs) were estimated for the experimental foliage based on dry matter (DM), CT, or crude protein (CP) intake. During both study stages, individual fecal egg counts were estimated. The JSI patterns of different plant species, based on DM, CT, or CP, were similar irrespective of infection level during stage 1 (HI, MI, and NI) or no GIN infection (stage 2). Thus, irrespective of GIN infection, goats actively selected M. bahamensis (high CT, low CP content) and V. dentata (negligible CT, high CP content) but avoided G. floribundum (high CT, low CP content) and L. leucocephala (medium CT and high CP content). Thus, natural GIN infection did not influence goats' foliage selection.

Phytochemicals in animal health: diet selection and trade-offs between costs and benefits

Many plant tissues contain plant secondary compounds (PSC), which have long been recognised as defensive chemicals that deter herbivory via their toxic effects. However, herbivores may also benefit from including PSC into their diets. Plant-derived phenolics, terpenes and alkaloids have antiparasitic properties and sesquiterpene lactones have antibacterial, antifungal and antiparasitic properties. These actions are in part a consequence of the negative actions that PSC exert across several trophic levels, including the bacteria, parasites and fungi that inhabit herbivores' bodies. Given the dual action, toxin and medicine, it is possible to hypothesise that self-selection of PSC by herbivores should occur when the benefits outweigh the costs of PSC ingestion. Recent research suggests that sheep and goats self-medicate against parasitic infections. They increase preference for condensed tannin-containing foods when experiencing a parasitic burden. This behaviour improves health; it is triggered by parasitism and weakens when parasitism subsides. However, the causes underlying these responses are not straightforward when viewed under a unidimensional cost-benefit analysis. This is because the intensity of antinutritional/toxic and medicinal effects of PSC is not static or just dependent upon the isolated post-ingestive effects of single PSC. Nutrient-PSC and PSC-PSC interactions, social models, as well as feeding patterns, all influence the perceived net benefit of incorporating medicines into a diet. A better understanding of the net benefit of self-medication in complex feeding environments will allow for the development of innovative managing strategies aimed at providing the food alternatives and conditions for improving the nutrition, health and welfare of grazing animals.

Drugs as instruments: a new framework for non-addictive psychoactive drug use

Most people who are regular consumers of psychoactive drugs are not drug addicts, nor will they ever become addicts. In neurobiological theories, non-addictive drug consumption is acknowledged only as a "necessary" prerequisite for addiction, but not as a stable and widespread behavior in its own right. This target article proposes a new neurobiological framework theory for non-addictive psychoactive drug consumption, introducing the concept of "drug instrumentalization." Psychoactive drugs are consumed for their effects on mental states. Humans are able to learn that mental states can be changed on purpose by drugs, in order to facilitate other, non-drug-related behaviors. We discuss specific "instrumentalization goals" and outline neurobiological mechanisms of how major classes of psychoactive drugs change mental states and serve non-drug-related behaviors. We argue that drug instrumentalization behavior may provide a functional adaptation to modern environments based on a historical selection for learning mechanisms that allow the dynamic modification of consummatory behavior. It is assumed that in order to effectively instrumentalize psychoactive drugs, the establishment of and retrieval from a drug memory is required. Here, we propose a new classification of different drug memory subtypes and discuss how they interact during drug instrumentalization learning and retrieval. Understanding the everyday utility and the learning mechanisms of non-addictive psychotropic drug use may help to prevent abuse and the transition to drug addiction in the future.

Parasites, Plants, and People

Anthelminthic resistance is acknowledged worldwide and is a major problem in Aotearoa New Zealand, thus alternative parasite management strategies are imperative. One Health is an initiative linking animal, human, and environmental health. Parasites, plants, and people illustrate the possibilities of providing diverse diets for stock thereby lowering parasite burdens, improving the cultural wellbeing of a local community, and protecting the environment.

The ecology and evolution of animal medication: genetically fixed response versus phenotypic plasticity

Animal medication against parasites can occur either as a genetically fixed (constitutive) or phenotypically plastic (induced) behavior. Taking the tritrophic interaction between the monarch butterfly Danaus plexippus, its protozoan parasite Ophryocystis elektroscirrha, and its food plant Asclepias spp. as a test case, we develop a game-theory model to identify the epidemiological (parasite prevalence and virulence) and environmental (plant toxicity and abundance) conditions that predict the evolution of genetically fixed versus phenotypically plastic forms of medication. Our model shows that the relative benefits (the antiparasitic properties of medicinal food) and costs (side effects of medicine, the costs of searching for medicine, and the costs of plasticity itself) crucially determine whether medication is genetically fixed or phenotypically plastic. Our model suggests that animals evolve phenotypic plasticity when parasite risk (a combination of virulence and prevalence and thus a measure of the strength of parasite-mediated selection) is relatively low to moderately high and genetically fixed medication when parasite risk becomes very high. The latter occurs because at high parasite risk, the costs of plasticity are outweighed by the benefits of medication. Our model provides a simple and general framework to study the conditions that drive the evolution of alternative forms of animal medication.

Ruminant self-medication against gastrointestinal nematodes: evidence, mechanism, and origins

Gastrointestinal helminths challenge ruminants in ways that reduce their fitness. In turn, ruminants have evolved physiological and behavioral adaptations that counteract this challenge. Ruminants display anorexia and avoidance behaviors, which tend to reduce the incidence of parasitism. In addition, ruminants appear to learn to self-medicate against gastrointestinal parasites by increasing consumption of plant secondary compounds with antiparasitic actions. This selective feeding improves health and fitness. Here, we review the evidence for self-medication in ruminants, propose a hypothesis to explain self-medicative behaviors (based on post-ingestive consequences), and discuss mechanisms (e.g., enhanced neophilia, social transmission) that may underlie the ontogeny and spread of self-medicative behaviors in social groups. A better understanding of the mechanisms that underlie and trigger self-medication in parasitized animals will help scientists devise innovative and more sustainable management strategies for improving ruminant health and well-being.

Reduced neophobia: a potential mechanism explaining the emergence of self-medicative behavior in sheep

Gastrointestinal helminths challenge ruminants in ways that reduce their fitness. In turn, ruminants have evolved physiological and behavioral adaptations that counteract this challenge. For instance, emerging behavioral evidence suggests that ruminants self-select medicinal compounds and foods that reduce parasitic burdens. However, the mechanism/s leading to self-medicative behaviors in sick animals is still unknown. We hypothesized that when homeostasis is disturbed by a parasitic infection, consumers should respond by increasing the acceptability of novel foods relative to healthy individuals. Three groups of lambs (N=10) were dosed with 0 (Control-C), 5000 (Medium-M) and 15000 (High-H) L3 stage larvae of Haemonchus contortus. When parasites had reached the adult stage, all animals were offered novel foods and flavors in pens and then novel forages at pasture. Ingestive responses by parasitized lambs were different from non-parasitized Control animals and they varied with the type of food and flavor on offer. Parasitized lambs consumed initially more novel beet pulp and less novel beet pulp mixed with tannins than Control lambs, but the pattern reversed after 9d of exposure to these foods. Parasitized lambs ingested more novel umami-flavored food and less novel bitter-flavored food than Control lambs. When offered choices of novel unflavored and bitter-flavored foods or different forage species to graze, parasitized lambs selected a more diverse array of foods than Control lambs. Reductions in food neophobia or selection of a more diverse diet may enhance the likelihood of sick herbivores encountering novel medicinal plants and nutritious forages that contribute to restore health.

Explaining human recreational use of 'pesticides': The neurotoxin regulation model of substance use vs. the hijack model and implications for age and sex differences in drug consumption

Most globally popular drugs are plant neurotoxins or their close chemical analogs. These compounds evolved to deter, not reward or reinforce, consumption. Moreover, they reliably activate virtually all toxin defense mechanisms, and are thus correctly identified by human neurophysiology as toxins. Acute drug toxicity must therefore play a more central role in drug use theory. We accordingly challenge the popular idea that the rewarding and reinforcing properties of drugs "hijack" the brain, and propose instead that the brain evolved to carefully regulate neurotoxin consumption to minimize fitness costs and maximize fitness benefits. This perspective provides a compelling explanation for the dramatic changes in substance use that occur during the transition from childhood to adulthood, and for pervasive sex differences in substance use: because nicotine and many other plant neurotoxins are teratogenic, children, and to a lesser extent women of childbearing age, evolved to avoid ingesting them. However, during the course of human evolution many adolescents and adults reaped net benefits from regulated intake of plant neurotoxins.

Cattle and sheep develop preference for drinking water containing grape seed tannin

Ingestion of small amounts of some types of condensed tannins (CTs) by ruminant livestock can provide nutritional, environmental and economic benefits. However, practical methods are needed to make these tannins more available to ruminant livestock. Results from previous trials with crude quebracho and black wattle tannin indicated that cattle and/or sheep would not preferentially drink water containing these tannins. Therefore, we conducted preference trials to determine if cattle and sheep would learn to prefer water containing purified grape seed tannin (GST) that provided up to 2% of their daily dry matter (DM) intake. After gradual exposure to increasing amounts of this tannin in water during a pre-trial period, five adult ewes and five yearling heifers fed lucerne (Medicago sativa) pellets (19% CP) were offered water and several concentrations of GST solutions for either 15 (sheep trial) or 20 days (cattle trial). We measured intake of all liquids daily. Concentrations of blood urea were also measured for heifers when they drank only tannin solutions or water. Both sheep and cattle developed preferences for water with GST in it over water alone (P < 0.01) although this preference appeared earlier in the trial for sheep than for cattle. For the sheep, mean daily intake of water alone and all tannin solutions (in total) was 0.6 and 6.1 l, respectively. For the cattle, mean daily intake of water and all tannin solutions in total was 21.8 and 20.6 l, respectively, in the first half of the trial and 10.8 and 26.1 l, respectively, in the second half of the trial. Compared with the other tannin solutions, both sheep and cattle drank more of the solution with the highest tannin concentration (2% of daily DM intake as GST) than of water on more trial days (P < 0.05). Ingestion of water with the highest concentration of GST reduced blood plasma urea concentration in the cattle by 9% to 14% (P ≤ 0.10) compared with ingestion of water alone. Results from the trials suggest that providing grape seed and perhaps other CTs via drinking water may be a practical way to introduce CTs into sheep and cattle diets.

Preference for tannin-containing supplements by sheep consuming endophyte-infected tall fescue hay

Tannins may bind to alkaloids in endophyte-infected (E+) tall fescue and attenuate fescue toxicosis. To test this hypothesis, thirty-two 4-mo-old lambs were randomly assigned to 4 treatments (8 lambs/treatment) in a 2 by 2 factorial design that included a basal diet of tall fescue hay [E+ or endophyte-free (E-)] supplemented with (TS) or without (CS) bioactive Quebracho tannins. The concentration of ergovaline in E+ fed in 2 successive phases was 65 ± 21 µg/kg (Phase 1) and 128 ± 4 µg/kg (Phase 2). After exposure to hays and supplements, all lambs were offered choices between TS and CS and between E+ and E- hays. During Phase 1, lambs offered E+ consumed more hay than lambs offered E- (P = 0.03). Lambs on E+/TS displayed the greatest intake of hay and the least intake of TS (P < 0.05). During Phase 2, when the concentration of ergovaline increased, lambs offered E+ consumed less hay than lambs fed E- (P < 0.0001). Lambs on E+/CS consumed less hay than lambs on E-/CS (P = 0.02), but hay intake by lambs on E-/TS and E+/TS did not differ (P = 0.96). Lambs preferred CS to TS during preference tests (P < 0.0001) and lambs on E+/TS ingested the least amounts of supplement TS and the greatest amounts of supplement CS (P = 0.001). Lambs offered E+ displayed greater body temperatures than lambs offered E- in both phases (P < 0.05). When offered a choice among the 3 hays, lambs previously exposed to E+ preferred E+ (low content of ergovaline) > E- > E+ (greater content of ergovaline; P < 0.001). Thus, decreased concentrations of ergovaline increased rectal temperatures, and affected intake of and preference for tannins and fescue hay. Quebracho tannins did not attenuate the effects of E+ on body temperature and feed intake. Ingestion of E+ reduced intake of quebracho tannins, suggesting that alkaloids in E+ antagonized ingestion of condensed tannins.

Manejo de parasitoses em sistema orgânico de produção de leite

Os sistemas agropecuários de produção orgânica respondem às necessidades do mercado e às crescentes preocupações dos consumidores, relacionadas à qualidade dos alimentos, ao respeito ao meio ambiente e ao bem-estar dos animais. Em tais sistemas de produção animal, o emprego de produtos químicos de síntese é severamente limitado. Assim, a conversão de um sistema de produção animal convencional em sistema de produção orgânica é acompanhada de alterações relacionadas à intensidade e à diversidade de infestação/infecção dos animais por ecto e endoparasitos, tornando indispensável o emprego de medidas profiláticas. O presente trabalho tem como objetivo expor as principais questões relacionadas ao manejo de parasitoses em sistemas orgânicos de produção de leite, assim como suas perspectivas de controle.

Why are dairy cows not able to cope with the subacute ruminal acidosis?

One of the largest challenges for the dairy industry is to provide cows with a diet which is highly energetic but does not negatively affect their rumens' functions. In highly productive dairy cows, feeding diets rich in readily fermentable carbohydrates provides energy precursors needed for maximum milk production, but simultaneously decreases ruminal pH, leading to a widespread prevalence of subacute ruminal acidosis. Maximizing milk production without triggering rumen acidosis still challenges dairy farmers, who try to prevent prolonged bouts of low ruminal pH mainly by proper nutrition and management practices. The animals try to avoid overeating fermentable feeds, as it causes negative consequences by disturbing digestive processes. The results of several experiments show that ruminants, including sheep and beef cattle, are able to modify some aspects of feeding behaviour in order to adjust nutrient intake to their needs and simultaneously prevent physiological disturbances. Particularly, such changes (e.g., increased preference for fibrous feeds, reduced intake of concentrates) were observed in animals, which were trying to prevent the excessive drop of rumen fluid pH. Thanks to a specific mechanism called "the postingestive feedback", animals should be able to work out such a balance in intake, so they do not suffer either from hunger or from negative effects of over-ingesting the fermentable carbohydrates. This way, an acidosis should not be a frequent problem in ruminants. However, prolonged periods of excessively decreased rumen pH are still a concern in dairy cows. It raises a question, why the regulation of feed intake by postingestive feedback does not help to maintain stable rumen environment in dairy cows?

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.