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A herbivore faces challenges while foraging-ongoing changes in its physiological condition along with variation in the nutrient and toxin concentrations of foods, spatially and temporally-that make selecting a nutritious diet a vital affair. Foraging behaviours arise from simple rules that operate across levels of resolution from cells and organs to individuals and their interactions with social and physical environments. At all these levels, behaviour is a function of its consequences: a behaviour operating on the environment to induce changes is itself changed by those events. Thus, behaviour emerges from its own functioning-behaviour selforganizes-not from that of its surroundings. This ostensible autonomy notwithstanding, no self-organizing system (cell, organ, or individual) is independent of its environs because existence consists of an ongoing exchange of energy and matter. According to this view, the notion of cause and effect is replaced with functional relationships between behaviours and environmental consequences. Changes in physical environments alter the distribution, abundance, nutritional, and toxicological characteristics of plants, which affect food preference. Social interactions early in life influence behaviour in various ways: animals prefer familiar foods and environments, and they prefer to be with companions. Animals in unfamiliar environments often walk farther, ingest less food, and suffer more from malnutrition and toxicity than animals in familiar environments. An individual's food preferences-and its ability to discriminate familiar from novel foods-arise from the functional integration of sensory (smell, taste, texture) and postingestive (effects of nutrients and toxins on chemo-, osmo-, and mechano-receptors) effects. The ability to discriminate among foods is critical for survival: all problems with poisonous plants are due to an inability to discriminate or a lack of alternatives. Animals eat a variety of foods as a result of nearing or exceeding tolerance limits for sensory and postingestive effects unique to each food. After eating any food too frequently or excessively, the likelihood increases that animals will eat alternative foods owing to exceeding sensory-, nutrient-, and toxin-specific tolerance limits. Cyclic patterns of intake of a variety of foods reflect seemingly chaotic interactions among flavours, nutrients, and toxins interacting along continua. [ABSTRACT FROM AUTHOR]

As environmental and health concerns of beef production and consumption mount, there is growing interest in agroecological production methods, including finishing beef cattle on pastures with phytochemically diverse grasses, forbs, and/or shrubs. The goal of this metabolomics, lipidomics, and fatty acid methyl ester profiling study was to compare meat (pectoralis profundus) of Black Angus cattle from two commercial US beef finishing systems (pasture-finished on Western U.S. rangeland; n = 18 and grain-finished in a Midwest U.S. feedlot; n = 18). A total of 907 out of 1575 compounds differed in abundance between pasture-finished and grain-finished beef samples (all, false discovery rate adjusted P < 0.05). Pasture-finished beef contained higher levels of phenolic antioxidants (2.6-fold), alpha-tocopherol (3.1-fold), nicotinate/vitamin B 3 (9.4-fold), choline (1.2-fold), myo-inositol (1.8-fold), and omega-3 fatty acids (4.1-fold). Grain-finished beef contained higher levels of gamma-tocopherol (14.6-fold), nicotinamide/vitamin B 3 (1.5-fold), pantothenate/vitamin B 5 (1.3-fold), and pyridoxine/vitamin B 6 (1.3-fold); indicating that feeding some grain (by-products) could be beneficial to increase levels of certain B-vitamins. Pasture-finished beef samples also displayed lower levels of oxidative stress (homocysteine, 0.6-fold; and 4-hydroxy-nonenal-glutathione, 0.4-fold) and improved mitochondrial function (1.3-fold) compared to grain-finished animals. Two potential metabolites of fluoroquinolone antibiotics, 2,8-quinolinediol and 2,8-quinolinediol sulfate, were only observed in grain-finished beef, though the source remains unknown. While pasture-finished cattle displayed improved markers of metabolic health and concentrated additional, potentially health-promoting compounds in their meat, our findings should not be interpreted as that grain-finished beef is unhealthy to consume. Randomized controlled trials in humans are required to further assess whether observed differences between pasture-finished and feedlot-finished beef have an appreciable effect on human health., (© 2024. The Author(s).)

Background: With rising concerns regarding the effects of red meat on human and environmental health, a growing number of livestock producers are exploring ways to improve production systems. A promising avenue includes agro-ecological practices such as rotational grazing of locally adapted ruminants. Additionally, growing consumer interest in pasture-finished meat (i.e., grass-fed) has raised questions about its nutritional composition. Thus, the goal of this study was to determine the impact of two common finishing systems in North American bison-pasture-finished or pen-finished on concentrates for 146 d-on metabolomic, lipidomic, and fatty acid profiles of striploins (M. longissimus lumborum)., Results: Six hundred and seventy-one (671) out of 1570 profiled compounds (43%) differed between pasture- and pen-finished conditions (n = 20 animals per group) (all, P < 0.05). Relative to pasture-finished animals, the muscle of pen-finished animals displayed elevated glucose metabolites (~ 1.6-fold), triglycerides (~ 2-fold), markers of oxidative stress (~ 1.5-fold), and proteolysis (~ 1.2-fold). In contrast, pasture-finished animals displayed improved mitochondrial (~ 1.3-fold higher levels of various Krebs cycle metabolites) and carnitine metabolism (~ 3-fold higher levels of long-chain acyl carnitines) (all P < 0.05). Pasture-finishing also concentrated higher levels of phenolics (~ 2.3-fold), alpha-tocopherol (~ 5.8-fold), carotene (~ 2.0-fold), and very long-chain fatty acids (~ 1.3-fold) in their meat, while having lower levels of a common advanced lipoxidation (4-hydroxy-nonenal-glutathione; ~ 2-fold) and glycation end-product (N6-carboxymethyllysine; ~ 1.7-fold) (all P < 0.05). In contrast, vitamins B 5 , B 6 , and C, gamma/beta-tocopherol, and three phenolics commonly found in alfalfa were ~ 2.5-fold higher in pen-finished animals (all P < 0.05); suggesting some concentrate feeding, or grazing plants rich in those compounds, may be beneficial., Conclusions: Pasture-finishing (i.e., grass-fed) broadly improves bison metabolic health and accumulates additional potential health-promoting compounds in their meat compared to concentrate finishing in confinement (i.e., pen-finished). Our data, however, does not indicate that meat from pen-finished bison is therefore unhealthy. The studied bison meat-irrespective of finishing practice-contained favorable omega 6:3 ratios (< 3.2), and amino acid and vitamin profiles. Our study represents one of the deepest meat profiling studies to date (> 1500 unique compounds), having revealed previously unrecognized differences in animal metabolic health and nutritional composition because of finishing mode. Whether observed nutritional differences have an appreciable effect on human health remains to be determined., (© 2023. The Author(s).)

We face an urgent and complex challenge to produce large amounts of healthful animal and plant foods for an estimated 10 billion people by 2050 while maintaining essential ecosystem services. To compound this challenge, we must do so while not further degrading our environment and conserving essential nutrients such as copper, magnesium, phosphorus, selenium, and zinc that are in short supply for fertilization. Much good research has been done, but to meet this challenge, we need to greatly increase on-farm and watershed-scale research including on-farm evaluations and demonstrations of the putative best combinations of stewardship techniques over multiple years in real-world settings, which are backed by data on nutrient inputs, soil, air, and water chemistry (fluxes) and water discharge. We also need to work with farmers, specialists, and generalists in highly creative interdisciplinary teams that resist forming silos and that use combinations of techniques linked to agroecology and industrial ecology in combination with state-of-the-art engineering. Some of these research and demonstration farms need to be in catchments prone to pollution of aquatic and terrestrial ecosystems with nitrogen, phosphorus, and other nutrients. Some promising approaches include mixed crop-livestock systems, although these alone may not be productive enough without updating to meet the dietary needs of an estimated 10 billion people by 2050. Other approaches could be state-of-the-art multi-trophic production systems, which include several species of plants integrated into production with vertebrates (e.g., ruminants, pigs, poultry), invertebrates (e.g., insects, earthworms) and fish, shrimp, or crayfish to utilize wasted feed and excreta, and recycle nutrients back to the animals (via plants or invertebrates) in the systems. To cut costs and increase desirable outputs, we must recycle nutrients much better within our food production systems and produce both animal and plant foods more efficiently as nutrients cycle through systems., (Published by Elsevier B.V.)

A new generation of plant-based meat alternatives-formulated to mimic the taste and nutritional composition of red meat-have attracted considerable consumer interest, research attention, and media coverage. This has raised questions of whether plant-based meat alternatives represent proper nutritional replacements to animal meat. The goal of our study was to use untargeted metabolomics to provide an in-depth comparison of the metabolite profiles a popular plant-based meat alternative (n = 18) and grass-fed ground beef (n = 18) matched for serving size (113 g) and fat content (14 g). Despite apparent similarities based on Nutrition Facts panels, our metabolomics analysis found that metabolite abundances between the plant-based meat alternative and grass-fed ground beef differed by 90% (171 out of 190 profiled metabolites; false discovery rate adjusted p < 0.05). Several metabolites were found either exclusively (22 metabolites) or in greater quantities in beef (51 metabolites) (all, p < 0.05). Nutrients such as docosahexaenoic acid (ω-3), niacinamide (vitamin B3), glucosamine, hydroxyproline and the anti-oxidants allantoin, anserine, cysteamine, spermine, and squalene were amongst those only found in beef. Several other metabolites were found exclusively (31 metabolites) or in greater quantities (67 metabolites) in the plant-based meat alternative (all, p < 0.05). Ascorbate (vitamin C), phytosterols, and several phenolic anti-oxidants such as loganin, sulfurol, syringic acid, tyrosol, and vanillic acid were amongst those only found in the plant-based meat alternative. Large differences in metabolites within various nutrient classes (e.g., amino acids, dipeptides, vitamins, phenols, tocopherols, and fatty acids) with physiological, anti-inflammatory, and/or immunomodulatory roles indicate that these products should not be viewed as truly nutritionally interchangeable, but could be viewed as complementary in terms of provided nutrients. The new information we provide is important for making informed decisions by consumers and health professionals. It cannot be determined from our data if either source is healthier to consume.

The health of livestock, humans, and environments is tied to plant diversity-and associated phytochemical richness-across landscapes. Health is enhanced when livestock forage on phytochemically rich landscapes, is reduced when livestock forage on simple mixture or monoculture pastures or consume high-grain rations in feedlots, and is greatly reduced for people who eat highly processed diets. Circumstantial evidence supports the hypothesis that phytochemical richness of herbivore diets enhances biochemical richness of meat and dairy, which is linked with human and environmental health. Among many roles they play in health, phytochemicals in herbivore diets protect meat and dairy from protein oxidation and lipid peroxidation that cause low-grade systemic inflammation implicated in heart disease and cancer in humans. Yet, epidemiological and ecological studies critical of red meat consumption do not discriminate among meats from livestock fed high-grain rations as opposed to livestock foraging on landscapes of increasing phytochemical richness. The global shift away from phytochemically and biochemically rich wholesome foods to highly processed diets enabled 2.1 billion people to become overweight or obese and increased the incidence of type II diabetes, heart disease, and cancer. Unimpeded, these trends will add to a projected substantial increase in greenhouse gas emissions (GHGE) from producing food and clearing land by 2050. While agriculture contributes one quarter of GHGE, livestock can play a sizable role in climate mitigation. Of 80 ways to alleviate climate change, regenerative agriculture-managed grazing, silvopasture, tree intercropping, conservation agriculture, and farmland restoration-jointly rank number one as ways to sequester GHG. Mitigating the impacts of people in the Anthropocene can be enabled through diet to improve human and environmental health, but that will require profound changes in society. People will have to learn we are members of nature's communities. What we do to them, we do to ourselves. Only by nurturing them can we nurture ourselves.

For addressing potential food shortages, a fundamental tradeoff exists between investing more resources to increasing productivity of existing crops, as opposed to increasing crop diversity by incorporating more species. We explore ways to use local plants as food resources and the potential to promote food diversity and agricultural resilience. We discuss how use of local plants and the practice of local agriculture can contribute to ongoing adaptability in times of global change. Most food crops are now produced, transported, and consumed long distances from their homelands of origin. At the same time, research and practices are directed primarily at improving the productivity of a small number of existing crops that form the cornerstone of a global food economy, rather than to increasing crop diversity. The result is a loss of agro-biodiversity, leading to a food industry that is more susceptible to abiotic and biotic stressors, and more at risk of catastrophic losses. Humans cultivate only about 150 of an estimated 30,000 edible plant species worldwide, with only 30 plant species comprising the vast majority of our diets. To some extent, these practices explain the food disparity among human populations, where nearly 1 billion people suffer insufficient nutrition and 2 billion people are obese or overweight. Commercial uses of new crops and wild plants of local origin have the potential to diversify global food production and better enable local adaptation to the diverse environments humans inhabit. We discuss the advantages, obstacles, and risks of using local plants. We also describe a case study-the missed opportunity to produce pine nuts commercially in the Western United States. We discuss the potential consequences of using local pine nuts rather than importing them overseas. Finally, we provide a list of edible native plants, and synthesize the state of research concerning the potential and challenges in using them for food production. The goal of our synthesis is to support more local food production using native plants in an ecologically sustainable manner.

We contend that palates link herbivores and humans with landscapes and consider how these relationships have changed historically. An attuned palate, which enables herbivores to meet needs for nutrients and self-medicate to rectify maladies, evolves from three interrelated processes: flavor-feedback associations, availability of phytochemically rich foods, and learning in utero and early in life to eat nourishing combinations of foods. That occurs when wild or domestic herbivores forage on phytochemically rich landscapes, is less common when domestic herbivores forage on monoculture pastures, is close to zero for herbivores in feedlots, and is increasingly rare for people who forage in modern food outlets. Unlike our ancestors, the palates of many individuals are no longer linked in healthy ways with landscapes. Industrial farming and selection for yield, appearance, and transportability diminished the flavor, phytochemical richness, and nutritive value of fruits and vegetables for humans. Phytochemically impoverished pastures and feedlot diets can adversely affect the health of livestock and the flavor and nutritive value of meat and milk products for humans. While flavors of produce, meat, and dairy have become blander, processed foods have become more desirable as people have learned to link synthetic flavors with feedback from energy-rich compounds that obscure nutritional sameness and diminish health. Thus, the roles plants and animals once played in nutrition have been usurped by processed foods that are altered, fortified, and enriched in ways that can adversely affect appetitive states and food preferences. The need to amend foods, and to take nutrient supplements, could be reduced by creating phytochemically rich plants and herbivores and by creating cultures that know how to combine foods into meals that nourish and satiate., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Two experiments were conducted to assess preference by sheep for endophyte-infected tall fescue growing in monoculture at least 5 m away from alfalfa (fescue-middle (FM)) over endophyte-infected tall fescue growing adjacent (0.2 to 1 m; fescue-alfalfa (FA)) to alfalfa (FA), and the effect of legume scent on preference for endophyte-infected tall fescue. In Experiment 1, 10 six-month-old lambs were offered for 12 days a choice of freshly harvested FA and FM. On days 13 and 14, lambs were offered the same choice, except cages (to allow access only to scent) containing freshly harvested alfalfa were put in the feeders containing FA, whereas cages containing freshly harvested FM were included with the feeders containing FM. Forage intake was measured 1 h after feeding and at three consecutive 2-h intervals thereafter. FA contained greater (P<0.002) concentrations of the alkaloid ergovaline (360 ± 27 ppm) and CP (8 ± 0.4%) than FM (219 ± 27 ppm and 6 ± 0.4%, respectively). Lambs preferred (P<0.05) FA to FM during the 1st hour of feeding, but the differences became smaller and disappeared in later feeding periods (P<0.005). Lambs offered FA with alfalfa scent or FM with FM scent preferred (P<0.05) FA but only on the 2nd day. In Experiment 2, 10 six-month-old lambs were offered a choice of FM with cages (to allow access only to scent) containing freshly harvested alfalfa or FM for 8 days. During the following 4 days, FM in the cages was replaced with freshly harvested sainfoin. Preference was greater (P<0.05) for FM offered with alfalfa scent than for FM offered with FM scent only on days 4 and 8. When lambs were offered FM with alfalfa or sainfoin in cages, they preferred (P<0.05) tall fescue with sainfoin scent over fescue with alfalfa scent, but intake was variable across hours and days (P<0.001). It is concluded that (1) lambs adjusted their intake of and preference for FA and FM over successive feeding bouts within each day, likely owing to an attempt to balance intakes of nutrients and alkaloids and (2) olfactory cues influenced preference, but to a lesser extent than nutrients and alkaloids in endophyte-infected tall fescue.

We determined if tall fescue in a mixture with either tannin-containing sainfoin or saponin-containing alfalfa affected cattle foraging behavior, performance, meat quality, and consumer acceptance of meat. Foraging behavior, BW, and pasture biomass before and after grazing were monitored when cattle strip-grazed 3 replications of 2 treatments from May through September 2010 (12 calves/replication) and from June through September 2012 (8 calves/replication). Animals were allowed a choice between tall fescue and sainfoin (SAN) or tall fescue and alfalfa (ALF) growing in strips (fescue, legume, and fescue-legume mixture). Incidence of use (scan samples) of legumes increased from the beginning to the end of the trials (P < 0.05), suggesting that cattle learned to mix legumes with tall fescue. Scan samples and assessments of pasture biomass removal revealed greater use of sainfoin than alfalfa when both legumes were abundant in the spring (P < 0.05); that pattern reversed toward the end of the growing season (P < 0.05) as the abundance of sainfoin declined more than that of alfalfa. Intake of forage per kilogram of gain was greater for SAN than for ALF in 2010 (P = 0.0003) and showed a tendency to be greater for SAN than ALF in 2012 (P = 0.19). There were no differences in ADG between SAN and ALF in either year (1 kg/d; P > 0.05). No incidences of bloat were detected. When cattle (3 calves/treatment in 2010 and 8 calves/treatment in 2012) were slaughtered in September to assess meat quality and consumer acceptance, carcasses were lean (4% to 6% fat content of the longissimus muscle), but compared with ALF, SAN had higher marbling scores, quality grades (Select versus Standard), and back fat thicknesses (P < 0.05) in 2012. Steaks from cattle finished on SAN were redder in color than steaks from cattle finished on ALF (P < 0.05; 2012). Meat samples from SAN and ALF showed some differences in unsaturated fatty acid profiles and volatiles concentrations (P < 0.05), but consumer acceptance did not differ between SAN and ALF (P > 0.05). Thus, cattle incorporated a lower-quality grass into their diets even when legumes were available ad libitum during most grazing trials. Choices between tall fescue and legumes differing in the type of secondary compound (tannins vs. saponins) and bloating potential influenced patterns of forage use by cattle and led to differences in meat quality.

Background: We hypothesized that eating a food containing saponins (SAP), or tannins (TAN) prior to foods containing the alkaloids gramine (GRA) or 5-methoxy-N,N-dimethyltryptamine (TRP) would provide benefits not possible when the alkaloid-containing foods were eaten alone., Methods: In Trial 1, four groups of five lambs were first offered food with SAP for 30 min followed by food with either GRA or TRP for 3.5 h in a 2 × 2 factorial arrangement of a completely randomized design that included alkaloid (GRA or TRP) with or without SAP. In Trial 2 TAN replaced SAP. All foods were isocaloric (3.3 Mcal kg⁻¹) and isonitrogenous (14% crude protein). Foods, fecal and urine samples were collected and analyzed for dry matter intake and apparent digestibility of dry matter, energy (in megajoules, MJ), nitrogen (N), and neutral detergent fiber., Results: Supplemental SAP did not affect digestibility of the parameters tested (P > 0.10). Supplemental TAN increased digestibility of N (g kg⁻¹, P = 0.04), N retained (g day⁻¹, P = 0.07), N digested (g day⁻¹, P = 0.06), and N retained/N consumed (g kg⁻¹, P = 0.07). However, digestibilities of dry matter (g kg⁻¹, P = 0.0026), energy (MJ 1000 MJ⁻¹, P = 0.003), neutral detergent fiber (g kg⁻¹, P = 0.008), and digested N retained (g kg⁻¹, P = 0.07) were lower for lambs fed TAN than for unsupplemented animals., Conclusions: Tannin supplementation can improve retention of nitrogen in animals fed alkaloid-containing grasses such as reed canarygrass and tall fescue. Combinations of forages with complementary primary and secondary compounds enable animals to maintain intake and improve nutrient utilization., (Copyright © 2012 Society of Chemical Industry.)

Herbivores prefer feeds that supply required nutrients and avoid those with excess nutrients and plant secondary compounds (PSC). Nevertheless, PSC such as condensed tannins can provide beneficial medicinal effects to herbivores as they act against infective diseases such as parasitism. The objectives of this study were to determine: (1) if parasitized lambs increased preference for a tannin-rich feed after they experienced the beneficial antiparasitic effects of condensed tannins relative to parasitized lambs that did not experience such benefits, and (2) if preference for the tannin-rich feed in the former group decreased when parasite burdens subsided. Twenty two lambs were familiarized with beet pulp and beet pulp+8% quebracho tannins (beet pulp+tannins) and choices were given between the two feeds (initial preference tests). Subsequently, all animals were dosed with 10,000 L(3) stage larvae of Haemonchus contortus. Twenty-two days later, animals were exposed to beet pulp (Control group; n=11) or beet pulp+tannins (Treatment group; n=11) during 24 d. After exposure (during a parasitic infection) animals in both groups were given choices between the two feeds. Lastly, animals in both groups received an antiparasitic drench and were again given a choice between both feeds (after a parasitic infection). Lambs preferred beet pulp to beet pulp+tannins throughout the study (P<0.001) and no difference in preference for the tannin-rich feed was detected between groups during initial preference tests (P>0.05). However, during a parasitic infection, intake of and preference for the tannin-rich feed was higher for lambs that experienced the beneficial effects of condensed tannins while parasitized (Treatment) than for lambs that did not (Control) (P<0.05). When parasitic infections were terminated by chemotherapy, differences between groups disappeared (P>0.05). Preference by the Treatment group for the tannin-rich feed was lower after than during a parasite infection (P<0.05). In contrast, preference by the Control group did not change during these periods (P>0.05). Lambs in the Treatment group displayed lower FEC than lambs in the Control group (Group × Sampling Date; P<0.05). These results show lambs learned about the antiparasitic effects of condensed tannins and increased their preference for the tannin-rich feed, which subsided after chemotherapy, indicating preference was due to parasite infection. These findings suggest management that allows animals to select tannin-rich feeds can enable parasitized animals to self-medicate., (Published by Elsevier B.V.)

This study determined whether early experiences by sheep with monotonous or diverse diets influence intake of unfamiliar flavors and feeds later in life. Thirty 2-mo-old lambs were randomly assigned to 3 treatment diets (n = 10): diverse (DIV), diverse with plant toxins (DIV+T), and monotonous (MON). Lambs in DIV received in 9 successive periods of exposure 4-way choice combinations of 2 foods high in energy and 2 foods high in protein from an array of 6 foods: 3 high in energy [beet pulp, oat grain, and a mix of milo:grape pomace (60:40)] and 3 high in digestible protein (DP) (soybean meal, alfalfa, corn gluten meal). Lambs in DIV+T received the same exposure as DIV, but 2 plant toxins, oxalic acid (1.5%) and quebracho tannins (10%), were randomly added to 2 of the feeds in each of the choice combinations. Lambs in MON received a monotonous balanced diet, made with a mixture of all 6 feeds detailed before. All treatments received their feed in 4 separate buckets. During exposure, treatments did not differ in total daily DMI (P = 0.31), but daily intake of ME was less (P < 0.02) and daily intake of DP was greater (P < 0.03) for lambs in DIV and DIV+T than for lambs in MON. Treatments did not differ in ADG or G:F (P > 0.05). After exposure, lambs were offered a familiar feed (wheat bran) containing novel flavors (maple, garlic, or bitter) and 2-way choices of novel feeds (fescue hay vs. corn distillers grains, rice vs. calf manna, and green peas vs. rolled oats). Intake of maple-flavored wheat bran tended (P = 0.08) to be greater for lambs in DIV than for lambs in DIV+T and MON. Intake of bitter-flavored and garlic-flavored wheat bran were greater (P = 0.03 and P = 0.04, respectively) for lambs in DIV and DIV+T than for lambs in MON. During 2-way choice trials, lambs in DIV, but not in DIV+T, showed greater intakes of fescue hay (P = 0.05) and rice (P = 0.04) than lambs in MON. Intake of green peas was greater (P = 0.03) for lambs in DIV and DIV+T than for lambs in MON. At the end of testing, lambs in DIV but not in DIV+T showed greater ADG than lambs in MON (P = 0.05). Thus, early exposure to diverse foods enhanced acceptance of novel flavors relative to early exposure to a monotonous ration. Early experience with diverse feeds plus plant toxins led to a less diverse diet than early experience with diverse feeds. Early exposure to diverse feeds may be beneficial in production systems that require rapid acceptance and high intake of unfamiliar feeds.

We determined whether plant diversity and sequence of plant ingestion affected foraging when cattle chose from plants that varied in concentrations of alkaloids, tannins and saponins. We hypothesized cattle that ate high-alkaloid grasses (endophyte-infected tall fescue (TF) or reed canarygrass (RCG)) would prefer forages high in tannins (birdsfoot trefoil, BFT+) or saponins (alfalfa, ALF+), because tannins and saponins can bind to alkaloids, presumably reducing their absorption. We further hypothesized that forages with tannins or saponins consumed before, rather than after, foraging on high-alkaloid grasses would promote greater use of those grasses presumably by binding to alkaloids, thereby reducing their absorption. In Phase 1, cattle (n = 32) grazed on either high (+) or low (-) alkaloid grass (TF or RCG) pastures for 30 min each morning at 0600 h and were then offered a choice of BFT+, BFT-, ALF+ and ALF- for 60 min each day for 12 days. In Phase 2, cattle (n = 32) were first offered a choice of BFT+ or ALF+ for 30 min at 0600 h and then placed on grass (TF+ or -, or RCG+ or -) pastures for 60 min for 12 days. In both phases, we had four spatial replications of four treatments with 2 per calves assigned to each of the 16 replications per treatment combinations. Scan samples of individuals at 2-min intervals were used to determine incidence of foraging on each plant species (%). Cattle grazed more on RCG than on TF in Phases 1 (62% v. 27%; P = 0.0015) and 2 (71% v. 32%; P = 0.0005). In Phase 1, cattle that first foraged on RCG+ or TF- subsequently preferred ALF over BFT, whereas cattle offered RCG- or TF+ foraged on ALF and BFT equally. Foraging by cattle on RCG was cyclic during Phase 1, whereas cattle foraging on TF markedly decreased incidence of use of TF from 41% to only 16% by the end of the 12-day trial (P = 0.0029). Contrary to the cyclic (RCG) or steadily declining (TF) use of grasses in Phase 1, cattle steadily and dramatically increased foraging on both RCG and TF throughout Phase 2, when they first grazed BFT+ or ALF+ followed by high-alkaloid grasses (P = 0.0159). Our findings suggest that in plant species the sequence of ingestion influenced foraging behavior of cattle and that secondary compounds influenced those responses.

Background: We hypothesized that alfalfa (ALF) or birdsfoot trefoil (BFT) eaten prior to a meal of endophyte-infected tall fescue (TF) or reed canarygrass (RCG) would provide benefits not possible when TF or RCG are eaten alone. In trial 1, four groups of five lambs were first offered ALF for 30 min followed by either TF or RCG for 3.5 h in a 2 × 2 factorial arrangement of a completely randomized design that included grass (TF or RCG) with or without ALF. Trial 2 was similar to trial 1 except we used a new group of lambs fed BFT. Forage, fecal and urine samples were collected and analyzed for dry matter intake and apparent digestibility of dry matter, energy (in Kcal), nitrogen and neutral detergent fiber., Results: A meal of either ALF or BFT prior to eating TF or RCG caused lambs to eat more total dry matter and nitrogen (both in g d⁻¹) and energy (in MJ d⁻¹) than lambs fed only TF or RCG (P < 0.05). Lambs fed ALF slightly reduced intake of TF and RCG relative to unsupplemented animals. Lambs fed BFT ate slightly less RCG, but much more TF than unsupplemented animals (P < 0.10). Lambs ate much less BFT than ALF, but they were stimulated to eat TF to a greater degree by BFT than by ALF., Conclusions: The enhanced intake of TF by lambs provided BFT, as well as the greater nutrient intake by lambs fed legumes and grasses was likely due in part to complementary profiles of alkaloids, saponins, and tannins., (Copyright © 2011 Society of Chemical Industry.)

This study determined whether early experiences by sheep to monotonous or diverse diets influence: (1) plasmatic profiles of cortisol, a hormone involved in stress responses by mammals, before and after an ACTH challenge, (2) the readiness to eat new foods in a new environment, (3) general fearfulness and response to separation--as measured by the open field test (OFT) and stress induced hyperthermia (SIH)--and (4) the link between (2) and (3). Thirty, 2-mo-old lambs were randomly assigned to 3 treatments (10 lambs/treatment). Lambs in one treatment (Diversity--DV) received in successive periods of exposure all possible 4-way choice combinations of 2 foods high in energy and 2 foods high in protein from an array of 6 foods: 3 high in energy (beet pulp, oat grain, and a mix of grape pomace:milo [40:60]) and 3 high in protein (soybean meal, alfalfa, corn gluten meal). Lambs in another treatment (DV+T) received the same exposure described for DV but two phytochemicals, oxalic acid (1.5%) and quebracho tannins (10%) were randomly added within any period of exposure to foods high in energy or to foods high in protein. Lambs in the third treatment (Monotony--MO) received a monotonous balanced ration containing all 6 foods fed to the other groups. After exposure, lambs were offered a choice of the aforementioned 6 foods (DV; DV+T) or the monotonous diet (MO). Lambs were intravenously injected with ACTH 1 h after food presentation, and sampled at 1, 2, and 3 h post feeding for determinations of plasma cortisol concentrations. Reluctance to eat novel flavored foods (onion-, coconut- and cinnamon-flavored wheat bran), open field behavior, and SIH was assessed in all treatments. Lambs in MO showed greater concentrations of plasma cortisol 1 h after food presentation than lambs in the DV or DV+T treatments (P=0.04). However, the difference was small and no differences among treatments were detected after an ACTH challenge (P>0.1). Lambs in DV consumed more onion-flavored wheat bran than lambs in MO (P=0.05). Lambs in DV also showed a greater cumulative consumption of novel flavors on d 2 than lambs in MO (treatment×day; P=0.01). Lambs in DV showed lower increase in rectal temperature (P=0.07) than lambs in MO. Only lambs in DV exhibited a positive relationship between consumption of cinnamon-flavored wheat bran and attempts of escape (R(2)=0.58; P=0.02). Our results suggest that exposure to diverse foods early in life may be less stressful than exposure to monotonous rations, as measured by plasma cortisol concentrations after food ingestion, and by changes in rectal temperature after exposure to the OFT. Lambs exposed to diverse diets early in life may also increase the initial acceptance of new flavors in novel environments relative to lambs exposed early in life to monotonous diets., (Published by Elsevier Inc.)

We determined if sequence of ingestion affected use of endophyte-infected tall fescue (TF) when cattle also grazed birdsfoot trefoil (BFT) or alfalfa (ALF). Based on chemical characteristics of TF (alkaloids), BFT (tannins), and ALF (saponins), we hypothesized that cattle first allowed to graze ALF or BFT would subsequently spend more time grazing TF than cattle that first grazed TF followed by ALF or BFT. Sixteen bred heifers (478 ± 39 kg initial BW) were randomly assigned to 4 replicated pasture units. Each replicated unit consisted of 4 treatment sequences (TF → BFT, TF→ALF, BFT → TF, or ALF→TF), with 2 cows per sequence. Pastures were in the vegetative stage of growth at a height of 20 to 30 cm and provided ad libitum forage to cattle. We recorded foraging on TF, BFT, and ALF using scan sampling of individuals at 2-min intervals. The study was conducted in 4 phases run sequentially, for a total of 30 d. In phases 1 and 3, cattle in group 1 grazed TF pastures for 45 min and were then moved to BFT pastures for the next 45 min (TF→BFT); cattle in group 2 grazed in the reverse sequence (BFT → TF). In phases 2 and 4, cattle in group 1 grazed TF pastures for 45 min and then subsequently grazed ALF pastures for the remaining 45 min (TF→ALF); cattle in group 2 grazed in the reverse sequence (ALF→TF). Sequence of plant ingestion affected food selection. In phase 1, scans revealed grazing of TF by heifers was cyclic, and heifers tended to have more scans (P = 0.52) grazing TF when they grazed BFT → TF; scans for heifers grazing TF were consistently greater (P < 0.05) throughout phase 3 of the trial. In phase 2, heifers that grazed in the sequence ALF→TF spent considerably more scans (P = 0.03) foraging on TF from d 4 to 10 than heifers that grazed in the sequence TF→ALF, and they remained greater throughout phase 4 of the trial. Although the sequence ALF→TF appeared to be more effective than BFT → TF, consistent with the hypothesis of a complementary relationship between the steroidal alkaloids in TF and saponins in ALF, tannin concentrations in BFT were minimal (1.8%), which likely reduced the presumed inactivation of alkaloids by tannins. We also speculate that heifers needed to learn about the positive postingestive influence of sequence, a notion consistent with more similar scans spent foraging BFT and TF early in phases 1 (BFT → TF) and 2 (ALF→TF), and with the consistent and marked increase in scans spent foraging on TF for animals foraging in phases 3 (BFT → TF) and 4 (ALF→TF).

We learned previously that red-winged blackbirds (Agelaius phoeniceus) use affective processes to shift flavor preference, and cognitive associations (colors) to avoid food, subsequent to avoidance conditioning. We conducted three experiments with captive red-winged blackbirds to reconcile varied consequences of treated food with conditioned sensory cues. In Experiment 1, we compared food avoidance conditioned with lithium chloride (LiCl) or naloxone hydrochloride (NHCl) to evaluate cue-consequence specificity. All blackbirds conditioned with LiCl (gastrointestinal toxin) avoided the color (red) and flavor (NaCl) of food experienced during conditioning; birds conditioned with NHCl (opioid antagonist) avoided only the color (not the flavor) of food subsequent to conditioning. In Experiment 2, we conditioned experimentally naïve blackbirds using free choice of colored (red) and flavored (NaCl) food paired with an anthraquinone- (postingestive, cathartic purgative), methiocarb- (postingestive, cholinesterase inhibitor), or methyl anthranilate-based repellent (preingestive, trigeminal irritant). Birds conditioned with the postingestive repellents avoided the color and flavor of foods experienced during conditioning; methyl anthranilate conditioned only color (not flavor) avoidance. In Experiment 3, we used a third group of blackbirds to evaluate effects of novel comparison cues (blue, citric acid) subsequent to conditioning with red and NaCl paired with anthraquinone or methiocarb. Birds conditioned with the postingestive repellents did not avoid conditioned color or flavor cues when novel comparison cues were presented during the test. Thus, blackbirds cognitively associate pre- and postingestive consequences with visual cues, and reliably integrate visual and gustatory experience with postingestive consequences to procure nutrients and avoid toxins., (Published by Elsevier Inc.)

Nutrition is an important aspect of welfare, and in most recommendations for the welfare of animals adequate nutrition is a primary requirement. However, in intensive livestock production systems the decision for adequate nutrition is made based on traditional paradigms of feeding monotonous rations or plant monocultures, frequently with excesses or imbalances of nutrients relative to the individuals' physiology, which can compromise welfare. Individual ruminants can better meet their needs for nutrients and regulate their intake of secondary compounds when offered a variety of foods than when constrained to a single food, even if the food is nutritionally balanced. The concept of food variety is central because monotonous flavors and feeds and excess nutrients all cause animals to satiate, which in turn causes animals to eat a variety of foods. When offered a variety of foods, satiety for single foods stimulates the selection of a diverse diet and thus food intake, but when restricted to a monotonous diet satiety is aversive and limits food intake. Moreover, if a monotonous diet is aversive to animals then this could be stressful, even if monotony implies consuming a balanced diet. A diverse diet may also increase resistance to disease in ruminants, by allowing consumption of small amounts of compounds with antimicrobial/antiparasitic effects and immunity-enhancing properties. Herbivores also experience the benefits of ingesting compounds with medicinal (i.e. antiparasitic) benefits and they learn to prefer foods containing such compounds as their preferences are associatively conditioned by the food's homeostatic utility to the body. Such learned patterns of behavior begin in utero and feeding experiences early in life cause changes - neurological, morphological and physiological - in animals, which influence on their subsequent behavior and welfare. Such experiences with the environment enable animals to adapt to local diets and stressors and reduce the levels of fear. Finally, feeding behavior in farm animals could be an aid in the early detection and mitigation of pain or sickness, and as such become an important tool in the identification of welfare and health of animals before the appearance of clinical signs. Management strategies in ruminant production systems could benefit by allowing animals to manifest their feeding preferences, thereby acknowledging the animals' role as active players in feeding systems, instead of regarding them as passive entities that just respond to prescriptions and formulations.

Herbivores learn to select compounds that attenuate the aversive effects of plant secondary metabolites (PSM), but can they increase intake of PSM they typically avoid when these PSM provide medicinal effects? We hypothesized that herbivores learn to increase intake of PSM-containing feeds when experiencing a gastrointestinal parasitic infection. Ten lambs with natural gastrointestinal parasitic burdens (PB) and 10 nonparasitized lambs (NP) were offered a choice of alfalfa (Medicago sativa) and alfalfa mixed with 10% quebracho tannin (Schinopsis quebracho-colorado; alfalfa:tannins) before and after they were conditioned with the postingestive effects of tannins. Preference for alfalfa:tannins did not differ between groups before experiencing the postingestive effects of tannins (P = 0.85) or when parasite loads were terminated due to the administration of ivermectin (P = 0.18). In contrast, when tested with a parasite burden, lambs in PB consumed more alfalfa:tannins (P = 0.08), showed greater preference for alfalfa:tannins (P = 0.07), and consumed less alfalfa than lambs in NP (P = 0.06). Ingestion of tannins by lambs in PB was followed by reduced fecal egg counts (FEC; P = 0.006), and there was a direct proportional relationship between preference for alfalfa:tannins and FEC (P = 0.07). In summary, parasitized lambs increased their intake of alfalfa:tannins when they experienced a parasite burden, which suggests they self-medicated with tannins against parasites. Self-selection of PSM has implications for the quest for alternatives to chemoprophylaxis in the treatment and well-being of parasitized wild and domestic animals grazing in pasturelands and in confinement.

6-Hydroxycylohex-2-en-1-one (6-HCH) has been reported as a major chemical defense of the winter-dormant internodes of balsam poplar (Populus balsamifera) against feeding by herbivores such as the snowshoe hare (Lepus americanus). We report that the concentration of 6-HCH in the fall internodes is triggered by a single hard frost, and then undergoes an exponential decline through volatilization over the winter that results in barely detectable quantities by early spring. We conclude that the role of 6-HCH in the defense of mature balsam poplar is more complex than simply acting as a toxin. Rather, 6-HCH's role as a defensive agent must evolve over the course of the winter from being a co-toxin to a cue for a conditioned flavor aversion (CFA) to finally having no role by late spring.

Acaricides can be conveyed to ticks via the blood of their hosts. As fruit and kernel extracts from the Meliaceae family, and, in particular the tetranortriterpenoid azadirachtin (AZA) inhibits tick egg production and embryogenesis in the Ixodidae ticks, we investigated the effects of Neem Azal, an extract containing 43% AZA, given as a feed additive to lambs artificially infested with engorging adult Dermacentor vairiabilis ticks. After tick attachment, the lambs were allotted to three dietary treatments: AZA0 (control, n=10), AZA0.3 (n=5), and AZA0.6 (n=5), with feed containing 0%, 0.3%, and 0.6% AZA on DM basis, respectively. In half of the AZA0 lambs, ticks were sprayed on day 4 after attachment with an ethanol:water:soap emulsion containing 0.6% AZA (AZA0S). In spite of its very pungent odor, the neem extract was well accepted by all but one lamb. No differences were found between treatment groups in liver enzymes in blood, and there was no indication of toxicity. The plasma AZA concentrations after 7 and 14 days of feeding AZA were (4.81 and 4.35 microg/mL) for the AZA0.6 and (3.32 and 1.88 microg/mL) for the AZA0.3 treatments, respectively (P<0.0001). Treatments were not lethal to ticks, but tick weights at detachment were 0.64, 0.56, 0.48, and 0.37 g for ticks from the AZA0, AZA0.3, AZA0S, and AZA0.6 treatments (P<0.04), respectively, suggesting that blood AZA impaired blood-feeding. The highest mortality rate after detachment was for AZA0.6 (P<0.09). As AZA affects embryo development and ticks at the molting stages, we expect that following treatments of hosts for longer periods, one-host ticks will be more affected than the three-host tick D. variabilis.

Animals adapt to the variability of the external environment and to their changing internal needs not only by generating homeostatic physiological responses, but also by operating in the external environment. In this study, we determined whether sheep with a gastrointestinal parasite infection increased intake of a low-quality food containing a natural antiparasitic agent (tannins) relative to non-parasitized sheep. Four groups of lambs (n=8 lambs/group) were assigned to a 2 x 2 factorial design with parasitic burden (P=parasites; NP=no parasites) and the offer of a supplement containing tannins (yes, no) as the main factors. Parasitized lambs ate more of the tannin-containing food than non-parasitized lambs for the first 12 days of the study, when parasite burdens were high, but differences became smaller and disappeared toward the end of the study when parasite burdens decreased. This result suggests the lambs detected the presence of internal parasites or associated symptoms and modified their ingestion of an antiparasitic agent as a function of need.

We propose that the exploitation of the bioactive properties of secondary metabolites (SMs) by animals can provide a "treatment" against various challenges that perturb homeostasis in animals. The unified theoretical framework for the exploitation of SMs by animals is based on a synthesis of research from a wide range of fields and although it is focused on providing generalized predictions for herbivores that exploit SMs of plants, predictions can be applied to understand the exploitation of SMs by many animals. In this review, we argue that the probability of SM exploitation is determined by the relative difference between the cost of a homeostatic challenge and the toxicity of the SM and we provide various predictions that can be made when considering behavior under a homeostatic perspective. The notion that animals experience and respond to costly challenges by exploiting therapeutic SMs provides a relatively novel perspective to explain foraging behavior in herbivores, specifically, and behavior of animals in general. We provide evidence that animals can exploit the biological activity of SMs to mitigate the costs of infection by parasites, enhance reproduction, moderate thermoregulation, avoid predation, and increase alertness. We stress that a better understanding of animal behavior requires that ecologists look beyond their biases that SMs elicit punishment and consider a broader view of avoidance or selection of SMs relative to the homeostatic state. Finally, we explain how understanding exploitation of SMs by animals could be applied to advance practices of animal management and lead to discovery of new drugs.

Fear, a key aspect of temperament with important implications for both animal welfare and production, may be manifest in responses to novelty. Herbivores typically prefer the familiar to the novel, and they generally regard anything novel with caution (i.e., they are reluctant to eat novel foods). We hypothesized animals differ in their fearfulness towards food and non-food items due to individuality which is influenced by genetics and contrasting environmental experiences. We further hypothesized fear of unknown foods and environments are correlated. Our objective was to determine if sheep differ in their fear responses and whether or not there is a link between general fearfulness and response to separation - as measured by the open field test (OFT) and stress induced hyperthermia (SIH) - and the readiness to eat new foods. We assessed reluctance to eat novel foods, open field behavior, and SIH in two groups of sheep (Group 1: Rambouillet-Columbia-Finn-Targhee crossbreds; Group 2: composite Suffolk) raised under contrasting environmental conditions. Lambs in Group 1 showed lower number of bleats and higher SIH than lambs in Group 2. When offered novel foods, lambs in Group 1 were more reluctant to eat them than lambs in Group 2. There was a negative relationship between number of bleats in OFT and reluctance to eat novel foods. Thus, reluctance to eat novel foods and response to separation in the OFT behavior differed among animals and a correlation was found between these behaviors. Our results suggest that reluctance to ingest new foods is influenced by sociality. Individuals less responsive to social isolation (lower number of bleats) may be less cautious at accepting novel foods than individuals more responsive to social isolation. Such variability implies some individuals may be more adept at consuming diverse diets in diverse locations whereas others may be more adept at consuming single foods at fixed locations.

We tested the hypothesis that supplemental polyethylene glycol (PEG), a polymer that neutralizes the effects of tannins, would increase intake and preference of cattle for fresh-cut sericea lespedeza (SL; Lespedeza cuneata), a legume with high concentrations of condensed tannins. Sixteen crossbred steers (initial BW of 249 +/- 6.6 kg) were randomly assigned to 2 treatments: 1) grain supplement with PEG (PEG-S) and 2) grain supplement without PEG (control). To assess intake, we conducted a trial with 6 sample periods, each 6 d in duration, with steers fed SL and prairie hay (PH) in separate meals. Steers were fasted overnight and fed their respective supplements (with and without PEG) at 0800 h. Animals were then offered fresh-cut SL from 1050 to 1550 h, PH was fed from 1600 to 2000 h, and they were without food from 2000 to 0800 h the next day. To assess preference, we conducted 1-d tests in which steers had simultaneous access to SL and PH on the day following periods 2 to 6. As with the intake experiment, steers were fasted overnight and fed their respective supplements at 0800 h, but from 1050 to 1250 h all steers had access to SL and PH simultaneously. We weighed steers before and at the completion of the study and calculated ADG. Steers treated with PEG consumed more SL per unit of BW than control steers in periods 2 to 6 (period x treatment interaction, P < 0.001). In contrast, controls consumed more PH than steers given PEG (period x treatment x day interaction, P = 0.009). The PEG-S steers consumed more total DM (SL + PH) than controls in periods 3, 5, and 6 but not in periods 1, 2, and 4 (period x treatment interaction, P = 0.004). Sericea lespedeza intake as a percentage of total DMI was greater for the PEG-S steers every day except d 1 and 2 of period 1 (period x treatment x day interaction, P = 0.03). Averaged across the 5 preference tests, PEG-S steers selected a greater proportion of SL than did control steers (39 vs. 9%), and the magnitude of the difference was greater in the later tests (test x treatment interaction, P = 0.004). The PEG-S steers had greater ADG than controls (0.44 vs. 0.24 kg/d; P = 0.005). Our results indicate PEG increases intake of and preference for SL and suggest that PEG supplementation of cattle may increase intake of SL and improve ADG in pastures that contain SL.

Distension of the rumen limits feed intake by livestock. Ruminal dysfunctions due to bloat, which causes distension by accumulation of excessive gas within the rumen, also reduce feeding. We hypothesized that excessive levels of rumen distension cause feed aversions and that preference increases for feeds eaten in association with recovery from bloat. To test these hypotheses, we determined whether 12 commercial crossbred lambs (average initial BW of 43 +/- 2 kg) could associate ingestion of specific feeds with the consequences of increased intraruminal pressure and its subsidence. Six of the lambs were fitted with rumen cannulas and offered ground alfalfa for 30 min after a rubber balloon was inserted into the rumen of each animal and distended with air to volumes of 1.8, 2.5, or 4.5 L. Subsequently, balloons were deflated and alfalfa was offered again for a second period of 30 min. Feed intake was not affected when the balloon was not distended (P = 0.45 to 0.93), but distension reduced feed intake (P < 0.001) in direct proportion to the magnitude of distension at all 3 volumes (R(2) = 0.70). Relief from distension promoted a compensatory increase in feed intake (P = 0.006). During conditioning to determine if lambs acquired a preference for a feed associated with recovery from distension, fistulated lambs were offered novel feeds: wheat bran (group 1; n = 3) and beet pulp (group 2; n = 3), and the balloon was distended for 30 min. Feeds were then switched and the balloons were deflated (recovery). Control lambs (n = 6) received the same feeding protocol without the balloons. Lambs formed strong aversions to feeds associated with distension and preferred feeds associated with recovery (P = 0.001 to P = 0.10). No preferences or avoidances were observed in control lambs conditioned without rumen distension (P = 0.17 to P = 0.87). Thus, rumen distension and recovery from distension induced feed aversions and preferences, respectively, which may be critical in learning avoidance of bloat-inducing plants and preferences for plants and supplements that relieve the incidence of bloat.

Poor nutritional quality and increased content of secondary compounds can reduce consumption of Mediterranean shrubs by herbivores. In 2 sequential trials, we examined the effect of polyethylene glycol (PEG) and number of shrub species offered on daily intake of Mediterranean shrubs by 12 sheep and 12 goats. The PEG (25 g) was fed to experimental animals with barley. In trial 1 (6 shrubs), goats ate more (P = 0.0008) daily total shrub biomass than did sheep (60.7 vs. 45.9 +/- 2.6 g/kg of BW). There was a trend (P = 0.08) toward a positive PEG effect on total shrub intake, with PEG-supplemented animals consuming more total shrubs than controls (56.7 vs. 50.0 +/- 2.6 g/kg of BW). Trial 2 (using 3 shrubs) was a continuation of trial 1, except that animals were given less barley and treatment animals were given more PEG (50 g). Both sheep and goats showed a numerical decrease in total shrub intake from trial 1 to trial 2. Sheep receiving PEG ate more (P = 0.002) total shrubs than did controls, but no PEG effect was found for goats. Thus, PEG had a greater influence on sheep than goats when only 3 shrubs were offered, a result that may be related to the fact that fewer shrubs with complementary secondary compounds were offered and that goats appear to have a greater ability to consume and detoxify secondary compounds from Mediterranean shrubs. Overall, as the number and diversity of shrubs offered increased, supplemental PEG had less effect on increasing intake for both goats and sheep.

The availability of fossil fuels will likely decline dramatically during the first half of the twenty-first century, and the massive deficits probably will not be alleviated by alternative sources of energy. This seeming catastrophe will create opportunities for communities to benefit from foods produced locally in ways that nurture relationships among soil, water, plants, herbivores, and people to sustain their collective well being. Agriculture will be much more at the heart of communities than it is currently, but by necessity, it will no longer be so dependent on fossil fuels to power machinery or to produce fertilizers, herbicides, and insecticides to grow and protect plants in monocultures, antibiotics, and anthelmintics to maintain the health of herbivores, or nutritional supplements and pharmaceuticals to sustain humans. Rather, from soils and plants to herbivores and people, we will have to learn once again what it means to be locally adapted to the landscapes we inhabit. In the process of relearning these skills, plants will become more important as nutrition centers and pharmacies, their vast arrays of primary (nutrients) and secondary (pharmaceuticals) compounds useful in nutrition and health. There also will be a need, as in times past before our heavy reliance on fossil fuels, to produce livestock in easy-care systems that match seasonally-available forages with production needs and that match animals anatomically, physiologically, and behaviorally to local landscapes. This will mean reducing inputs of fossil fuels to increase profitability by 1) matching animal needs to forage resources; 2) selecting for animals that are adapted anatomically, physiologically, and behaviorally to local environments; 3) culling animals unable to reproduce with minimal help from humans; and 4) creating grazing systems that enhance the well-being of soils, plants, herbivores, and people.

If supplemental minerals are needed to promote optimal animal performance, what is the best way of providing them: free choice or in the diet? We hypothesized that herbivores discriminate among feeds containing Na, P, and Ca and modify their choices as a function of need. One group of lambs was fed a basal diet low in P and high in Ca (low P-high Ca), whereas another group was fed a basal diet high in P and low in Ca (high P-low Ca). After 73 d of exposure to the unbalanced diets, the lambs were conditioned by offering flavored grape pomace containing NaCl, CaCO(3), or NaH(2)PO(4). Preference for pomace + minerals was determined when all lambs were fed a basal diet of alfalfa pellets and barley grain (initial preference) and during 4 phases. Phases 1 and 2 occurred after 40 and 67 d of feeding the unbalanced basal diets, phase 3 occurred after conditioning with NaCl, CaCO(3), or NaH(2)PO(4), and phase 4 occurred 22 d after the groups were moved to 2 new (separate) locations so the animals in the different groups could not eat dirt, urine, or feces from the other pen. Preference for pomace did not differ between the groups during the initial preference tests (P = 0.62); both groups preferred NaCl > CaCO(3) = NaH(2)PO(4) (P < 0.001). As the study progressed, and lambs fed low P-high Ca had lower P and greater Ca concentrations in serum than lambs fed high P-low Ca (P < 0.001), the preference between groups diverged. In phase 2, lambs in high P-low Ca continued to prefer NaCl (P < 0.001), but lambs in low P-high Ca preferred NaH(2)PO(4) (P < 0.05). After conditioning, both groups preferred NaCl = NaH(2)PO(4) > CaCO(3) (P < 0.01 to 0.11). After the groups were moved to different locations, lambs fed low P-high Ca showed the lowest concentration (3.7 mg/dL) of inorganic P in serum for all phases (P < 0.001), and they preferred NaH(2)PO(4) > NaCl = CaCO(3) (P < 0.001). In contrast, lambs in high P-low Ca avoided NaH(2)PO(4) (P < 0.05). Lambs offered high P-low Ca showed a greater preference for CaCO(3) (P = 0.12) and NaCl (P < 0.05) and a lower preference for NaH(2)PO(4) compared with lambs fed low P-high Ca (P < 0.001). In summary, lambs discriminated among different flavored feeds containing NaCl, CaCO(3), and NaH(2)PO(4) and displayed preferences as a function of the mineral imbalance in their basal diets. Thus, it may be possible to feed Ca and P supplements free choice, such that individual animals within a group can manifest preferences based on their specific needs.

The relationship between food flavors and postingestive feedback enables mammalian herbivores to procure nutrients and avoid toxins within ever-changing environments. We conducted four experiments with red-winged blackbirds (Agelaius phoeniceus) in captivity to determine the relative roles of color and flavor cues paired with negative postingestive feedback. We first conducted baseline tests to assess preferences for colors and flavors. All blackbirds preferred red- to blue-colored food, and they preferred umami- (l-alanine) flavored to bitter/astringent food (tannic acid). We observed no difference in consumption of salty (NaCl) vs sour (citric acid) foods during baseline tests (i.e., neutral flavors). We then conditioned experimentally naïve blackbirds with intraperitoneal injections of lithium chloride (LiCl) to avoid food treated with red and l-alanine, or red and NaCl (n=30 birds per conditioning group). Subsequent to conditioning with LiCl, three test groups were established from each conditioned group to evaluate color and flavor preferences, and preferences for novel color-flavor pairings (e.g., red/tannic acid vs blue/l-alanine). Blackbirds avoided red and salty food throughout the 4-day test. Avoidance conditioned with LiCl extinguished for preferred flavors, but not for colors, of food. Conditioning affected indifference for the otherwise preferred flavor and avoidance for the otherwise neutral flavor. Relative to the neutral-flavor conditioning group, the group conditioned with a preferred flavor exhibited stronger conditioned avoidance of colored food. Unlike conditioned flavor avoidance, birds were conditioned to avoid red food only when blue food was made familiar prior to conditioning. Collectively, these results illustrate that blackbirds used affective processes (flavor-feedback relationships) to shift preference for both novel and familiar flavors, and cognitive associations (colors) to avoid food, subsequent to toxin exposure. We discuss the opportunities afforded by affective and cognitive processing for reducing agricultural damage caused by blackbirds.

Traditional production systems have viewed animals as homogeneous 'machines' whose nutritional and medicinal needs must be provided in a prescribed manner. This view arose from the lack of belief in the wisdom of the body to meet its physiological needs. Is it possible for herbivores to select diets that meet their needs for nutrients and to write their own prescriptions? Our research suggests it is. Herbivores adapt to the variability of the external environment and to their changing internal needs not only by generating homeostatic physiological responses, but also by operating in the external environment. Under this view, food selection is interpreted as the quest for substances in the external environment that provide homeostatic utility to the internal environment. Most natural landscapes are diverse mixes of plant species that are literally nutrition centres and pharmacies with vast arrays of primary (nutrient) and secondary (pharmaceutical) compounds vital in the nutrition and health of plants and herbivores. Plant-derived alkaloids, terpenes, sesquiterpene lactones and phenolics can benefit herbivores by, for instance, combating internal parasites, controlling populations of fungi and bacteria, and enhancing nutrition. Regrettably, the simplification of agricultural systems to accommodate inexpensive, rapid livestock production, coupled with a view of secondary compounds as toxins, has resulted in selecting for a biochemical balance in forages favouring primary (mainly energy) and nearly eliminating secondary compounds. There is a global need to create a more sustainable agriculture, with less dependence on external finite resources, such as fossil fuels and their environmentally detrimental derivatives. Self-medication has the potential to facilitate the design of sustainable grazing systems to improve the quality of land as well as the health and welfare of animals. Understanding foraging as the dynamic quest to achieve homeostasis will lead to implementing management programs where herbivores have access not only to diverse and nutritious foods but also to arrays of medicinal plants.

The availability of different forages varies across landscapes, but little is known about how proportional consumption of different foods affects food intake and the use of landscapes. The relative amounts of nutrients and plant secondary metabolites (PSM) consumed by herbivores may influence forage intake and animal fitness in landscapes dominated by plants with PSM. Our objective was to determine if the relative availability of nutritious foods that contain PSM affected food preference and intake by lambs. Lambs in three treatments (eight lambs/treatment) were offered two PSM-containing foods at different relative availabilities: treatment 1-ad libitum terpene- and 100-g tannin-containing food, treatment 2 -- ad libitum tannin- and 100-g terpene-containing food, and treatment 3 -- ad libitum access to both tannin- and terpene-containing foods. We measured intake of individual foods and total intake of PSM-containing foods during conditioning and a preference test, where animals were offered both PSM-containing foods ad libitum. When lambs were fed 100 g of the tannin-containing food, they ingested more terpene and total PSM (P < 0.05) than when both PSM were offered ad libitum, but limiting terpenes did not affect intake of tannin or total intake of PSM (P > 0.10). During preference tests, all groups preferred tannins over terpenes, but lambs in the treatment fed 100 g of tannin had a higher preference for terpenes than did lambs in the other two treatments (P < 0.10). These results support the notion that the relative amounts of PSM consumed affects intake and preference for PSM-containing foods by herbivores.

We hypothesized that toxins and nutrients in foods interact to influence foraging behavior by herbivores. Based on this hypothesis we predicted that 1) terpenes in big sagebrush (Artemisia tridentata) influence intake and preference in sheep for diets varying in sources of nonstructural (barley grain) and structural (sugar beet pulp) carbohydrates, and 2) these effects are due to the differential effects of terpenes on fermentation products and apparent digestibility of each class of carbohydrates. Lambs were fed 2 isoenergetic and isonitrogenous diets with varying proportions of the same ingredients (beet pulp- and barley grain-based diet) or offered a choice between the 2 diets; all feeds were fed without and with terpenes, in consecutive periods. We also compared intake and preference of the beet pulp-and barley-based diets before and after the lambs ate a meal of sagebrush. Finally, we assessed the effect of terpenes on ruminal variables and in vivo digestibility. Lambs ate less when fed beet pulp or when they were offered a choice of diets with terpenes (P < 0.001), and intake of the beet pulp-based diet was the most affected (P < 0.05). Lambs preferred the beet pulp-to the grain-based diet with terpenes, but their preference reversed when terpenes were removed from the diets (P < 0.05). When lambs were offered both diets, intake and preference did not differ (P > 0.20) before eating sagebrush, but they preferred the beet pulp-based diet after eating sagebrush (P < 0.05). Intake of sagebrush did not differ among groups consuming the test diets (P = 0.21). Addition of terpenes to both diets increased the digestibility of DM, NDF, and ADF and decreased concentrations of total VFA and acetate (P < 0.05). Terpenes also depressed butyrate concentration in the barley-based diet (P < 0.05). Propionate concentrations were not affected by terpenes in either feed (P = 0.63). In summary, the predominant type of feed ingredient (beet pulp, grain) ingested with terpenes influenced fermentation products, intake, and preference in lambs. The source of energy from supplements, or other plants in the diet, is likely to influence intake and preference for sagebrush in sheep foraging on rangelands. Moreover, ingesting terpenes from sagebrush may also influence intake and preference for other plant species or supplements.

We hypothesized that lambs discriminate the postingestive effects of P and associate those effects with feed flavor to modify feed choices. Three predictions were tested based on this hypothesis: 1) lambs will modify preference for arbitrary flavors eaten during intraruminal infusions of NaH2PO4, 2) changes in preferences are more specific than changes in osmotic load induced by salts of Na; and 3) preference for P is inversely related to the concentration of inorganic P in blood. Thirty lambs were depleted of P by the offer of a P-deficient diet, allocated to 3 groups (10 lambs/group), and conditioned during 3 periods as follows: During conditioning period 1, lambs in each of 3 groups ate a poorly nutritious feed (grape pomace), flavored differently for each group, while water was infused into the rumen. During conditioning periods 2 and 3, lambs again ate grape pomace, with 2 new flavors now paired with infusion of an aqueous solution (126 mmol) of NaCl (conditioning period 2) or NaH2PO4 (conditioning period 3), rather than with water. After conditioning, all lambs were offered a choice of the 3 flavors during preference tests immediately after conditioning (period 1) and every 3 wk thereafter (periods 2, 3, and 4). During period 1, when serum inorganic P levels were greatest, lambs preferred flavors paired with water > NaCl > NaH2PO4 (P < 0.05). During periods 2 and 3, as inorganic P concentrations decreased in serum, lambs preferred flavors paired with NaH2PO4 > NaCl (period 2, P = 0.10; period 3, P = 0.05). Lambs preferred flavors paired with water > NaH2PO4 in period 2 (P < 0.001), but those differences disappeared in periods 3 and 4 (P > 0.05). During period 4, lambs preferred flavors paired with NaCl > NaH2PO4 (P < 0.10). The estimate of the slope for the linear relationship between intake of flavors paired with NaH2PO4 and serum inorganic P was negative (P < 0.0001), whereas estimates of the slopes for the relationships between intake of flavors paired with NaCl or water and serum inorganic P were not different from 0. Thus, preference for P was inversely related to the concentration of serum inorganic P. Our results suggest lambs discriminated among the postingestive effects of NaH2PO4, NaCl, and water and associated those effects with specific flavors. Lambs avoided flavors paired with NaH2PO4 during periods of P replenishment, and they increased preference for those flavors during periods of P need.

In grazing systems, forage availability is a function of herbivore density, which can influence an animal's ability to be selective. In turn, the influence of food availability on selectivity has the potential to influence plant biodiversity. We hypothesized that the ability of herbivores to mix toxin-containing foods in their diets is a function of the availability of nontoxic foods and the nutritional characteristics of the toxin-containing foods. We evaluated this hypothesis in two trials simulating different diet qualities (high-quality foods in trial 1, low-quality foods in trial 2). Within each trial, the four treatment groups were offered with different amounts of nutritious, familiar foods-10, 30, 50, and 70% of ad libitum intake-but were offered with ad libitum access to toxin-containing foods. Each lamb was presented with five foods, including three toxin-containing unfamiliar foods (terpenes, tannins, and oxalates) and two nutritious familiar foods (alfalfa and barley). In trial 1, as the availability of nutritious familiar foods decreased, animals ate more of all three toxin-containing foods. As the availability of nutritious alternatives increased, the pattern of selection shifted from terpenes to tannins and oxalates. In trial 2, animals also ate more toxins as the availability of nutritious alternatives decreased, but their pattern of diet mixing changed. Low availability of nutritious alternatives resulted in the animals eating more oxalates. During preference tests when all five foods were offered ad libitum, animals fed with 10, 30, 50, and 70% of ad libitum intake from trial 1 ate 49, 47, 41, and 38% of the three toxin-containing foods, respectively. The lower diet quality in trial 2 affected intake of the toxin-containing foods such that animals fed with 10, 30, 50, and 70% of ad libitum intake ate 37, 36, 29, and 27%, respectively, of the three toxin-containing foods. Thus, the quality of toxin-containing foods and the availability of nutritious alternatives interacted to modify the pattern of diet mixing by lambs.

The monoterpene 1,8-cineole is a major constituent of the essential oils that adversely influence intake of sage brush by herbivores, but little is known about the mechanisms of its action. We investigated the influence of 1,8-cineole on the feeding behavior of two groups of sheep, one group dosed intravenously and the other intra-ruminally. In the first study, we infused 40 mg/kg BW of 1,8-cineole intravenously into four lambs on wk 1, 2, and 4. In the second, we administered 125 mg/kg BW of 1,8-cineole into the rumen of four lambs as a single-bolus dose in wk 1 and 2. Lambs dosed intravenously spent less time feeding than controls (28 vs. 60 min; P<0.05), as did lambs dosed intra-ruminally (35 vs. 60 min; P<0.05). Dosed lambs ate less than controls during rumen dosing studies (P<0.05). For the intravenous infusion studies, rates of elimination did not differ among weeks (P<0.05). For the rumen infusion studies, however, the absorption rate constant increased from 0.035/min to 0.076/min from wk 1 to 2, while the absorption half-life declined from 24 to 10 min (P<0.05). Maximum plasma concentrations and time to reach maximum plasma concentrations were no faster in wk 2 than wk 1, but the primary elimination rate constant was 2.3 times higher in wk 2 (0.058/min) than in wk 1 (0.025/min) (P<0.05). Dosed lambs exhibited clinical effects-licking of lips, drowsiness, staggering, and 1,8-cineole-smelling breath-that were much more pronounced with intravenous than rumen infusions. Dosing did not affect the acid-base balance. Collectively, these data suggest 1) rapid absorption and distribution of 1,8-cineole was responsible for initiating satiety, while more prolonged excretion was responsible for the duration of the satiety effect, and 2) lambs more readily adapted to 1,8-cineole in the rumen-dose study than in the intravenous-dose study.

Burrow plugging is readily observed among mammals adapted for digging (i.e., fossorial mammals) as they create and maintain their burrows. We investigated the influence of light, burrow openings, and thermal environment as cues of pocket gopher (Thomomys mazama, Thomomys talpoides) behavior. When given free access to light and no light during artificial-burrow preference trials, both Thomomys spp. consistently plugged (i.e., avoided) light treatments. Burrow openings did not notably affect plugging behavior of T. mazama. Gophers (T. talpoides) plugged the artificial burrows within the light and cold (7 degrees C) treatments, but not within the no-light, and 18 or 31 degrees C treatments when light and temperature were varied independently. Whereas the presence of light and low ambient temperatures induce burrow maintenance by pocket gophers, these cues help meliorate adverse conditions within subsurface environs.

Interactions among nutrients and plant secondary metabolites (PSM) may influence how herbivores mix their diets and use food resources. We determined intake of a food containing a mix of terpenoids identified in sagebrush (Artemisia tridentata) when present in isoenergetic diets of increasing concentrations of protein (6, 9, 15, or 21% CP) or in isonitrogenous diets of increasing concentrations of energy (2.17, 2.55, 3.30, or 3.53 Mcal/kg). Lambs were offered choices between those diets with or without terpenes or between diets with terpenes and alfalfa hay. Intake of the diets with terpenes was lowest with the lowest concentrations of protein (6%) and energy (2.17 Mcal/kg) in the diets, and highest with diets of 15% CP and 3.53 Mcal/kg. In contrast, when terpenes were absent from the diets, lambs consumed similar amounts of all four diets with different concentrations of protein, and more of the diets with intermediate amounts of energy. When given a choice between the diet with or without terpenes, lambs preferred the diet without terpenes. When lambs were offered choices between terpene-containing diets and alfalfa, energy and protein concentrations influenced the amount of terpenes animals ingested. Energy densities higher than alfalfa, and protein concentrations higher than 6%, increased intake of the terpene-containing diet. Thus, the nutritional environment interacted with terpenes to influence preference such that lambs offered diets of higher energy or protein concentration ate more terpenes when forced, but not when offered alternative food without terpenes. The nutrients supplied by a plant and its neighbors likely influence how much PSM an animal can ingest, which in turn may affect the dynamics of plant communities, and the distribution of herbivores in a landscape. We discuss implications of these findings for traditional views of grazing refuges and varied diets in herbivores.

An analytical method is required for the analysis of monoterpenes in animal plasma to support a pharmacokinetic study. Monoterpenes common to sagebrush are extracted from sheep plasma by employing solid-phase extraction (SPE), followed by analysis of the extracts by gas chromatography with flame ionization detection. The analytes are quantitated versus an external standard and by comparison with a surrogate standard added to the sample prior to extraction. In addition to comparing the two quantitative methods, the storage stability of the analytes in plasma and SPE columns is evaluated. Both methods employed for quantitation yield precision suitable for pharmacokinetic studies. However, determination of monoterpenes residues versus external standards produces improved accuracy as compared with use of the surrogate standard. Some analyte loss is observed from plasma samples stored for five weeks at -12 degrees C. However, storage of extracts on the SPE columns affords excellent stability.

We determined if supplemental macronutrients or polyethylene glycol (PEG) influenced intake of a tannin diet. Sheep (lambs 5 mo age, 36 kg) and goats (kids 7 mo age, 32 kg) were fed supplements high in either energy or protein or offered a choice between the two supplements before and after receiving a meal containing 15% quebracho tannin. The effect of PEG, a compound that attenuates the negative effects of tannins, was assessed by offering PEG while animals consumed the tannin diet for 4 h/d. Intake of the tannin diet was influenced by both macronutrients and PEG. Animals that chose their own supplements or that received the high-protein supplement, consumed more of the tannin diet than animals fed the high-energy supplement: 34 and 36 vs 31 g/kg(0.75) (lambs) and 41 and 39 vs 34 g/kg(0.75) (kids), respectively (P < 0.05). Animals supplemented with PEG ate much more of the tannin diet than unsupplemented animals: 70 vs 39 g/kg(0.75) (lambs) and 63 vs 34 g/kg(0.75) (kids), respectively (P < 0.001). Sheep and goats consumed more tannin food when given PEG than when supplemented with macronutrients (51 and 38 g/kg(0.75), P < 0.001). Sheep and goats offered a choice between supplements consumed more CP than animals fed the high-energy supplement and more ME than animals fed the high-protein supplement (P < 0.05). In so doing, they selected a combination of foods that yielded a more balanced intake of macronutrients, while achieving high levels of intake of the tannin food. Sheep and goats can be used as an environmentally safe and economically sound means to reduce the abundance of tannin-rich vegetation. Macronutrients and PEG enhance use of tannin-containing plants, which may increase production of alternate forages and create a more diverse mix of species in a plant community.