Temporal and Spatial Influences on Fawn Summer Survival in Pronghorn Populations: Management Implications from Noninvasive Monitoring.

Monitoring vital rates allows managers to estimate trends in growth rates of ungulate populations. However, connecting the influence of nutrition on ungulate demography is challenging. Noninvasive sampling offers a low-cost, low-effort alternative for measuring nutritional indices, allowing for an increased understanding of the mechanistic relationships between environmental factors, nutrition, and specific population vital rates. We examined the temporal influence of intrinsic and extrinsic factors on pronghorn (Antilocapra americana) fawn recruitment. We collected fresh fecal samples from adult female pronghorn in five subpopulations spanning three sampling periods associated with critical maternal life-history stages (late gestation, early lactation, breeding season) for 2 years to investigate both intra- and interannual influences. Intrinsic factors were fecal glucocorticoid metabolites (FGMs), nutritional indices (fecal nitrogen (FN) and 2,6-diaminopimelic acid (DAPA)), and dietary composition (protein intake of forbs, graminoids, legumes, other, shrubs), while the extrinsic factor was vegetative greenness (normalized difference vegetation index (NDVI)). We found variations in DAPA, protein intake of forbs, variation in forb protein intake, and protein intake of legumes during late gestation positively influenced fawn recruitment. Fecal nitrogen during early lactation showed the strongest positive influence on the recruitment of any measured parameter. Finally, breeding season NDVI and the variation in DAPA values positively influenced the subsequent year's fawn recruitment. Our longitudinal study enabled us to investigate which parameter was most important to specific periods of fawn development and recruitment. We combined the results across five subpopulations, but interpretation and subsequent management decisions should be made at the subpopulation level such that pronghorn subpopulations with low recruitment can be positively influenced by increasing nitrogen on the landscape available to adult females during the early lactation period. As the use of noninvasive monitoring methods continues to expand, we believe our methodologies and results can be broadly applied to other ungulate monitoring programs.

Seasonal shifts in pronghorn antelope (Antilocapra americana) diets under a new lens: Examining diet composition using a molecular technique.

Foraging is one of the most fundamental activities contributing to the maximization of an animal's fitness, and thus herbivores must optimize their diet selection and intake to meet their nutrient demands for survival, growth, and reproduction. Using plant DNA barcoding, we determined diet composition of five subpopulations of adult female pronghorn antelope (Antilocapra americana) grazing rangelands in southern and southeastern Idaho, USA. Fecal samples were collected for two years (2018-2019), and across metabolically-important adult female life history stages (late gestation, early lactation, breeding season). Plant DNA barcoding yielded 137 detected species within pronghorn diets across subpopulations and sampling periods with forbs being the most abundant. Pronghorn dietary functional group composition ranged from 52.2-60.3% from forbs followed by shrubs (22.6-28.2%), graminoids (8.7-15.7%), and legumes (5.5-9.6%). Dietary protein intake was also highest from forbs and ranged from 32.4-62.4% followed by graminoids (1.2-43.1%), shrubs (18.7-21.3%), and legumes (2.6-7.4%). We found significant intra- and interannual differences in the mean number of genera-based plant detections in pronghorn diets. Dietary protein intake of cultivated legumes (e.g., alfalfa [Medicago sativa] and sainfoin [Onobrychis viciifolia]) was lower than expected, ranging from <1.0-30.8%, suggesting that even within an agricultural-dominated landscape, factors other than plant nutritional composition contributed to pronghorn diets. Although the plant DNA barcoding technique exhibits limitations, it demonstrated potential for elucidating pronghorn dietary species richness, particularly for plants consumed in small proportions, as well as for observing temporal fluctuations in functional group composition and dietary protein intake explained through the interplay between environmental factors, plant chemical composition, and the animals' physiological needs.

Grazing diverse combinations of tanniferous and nontanniferous legumes: implications for foraging behavior, performance, and hair cortisol in beef cattle.

A diversity of forages with different types and concentrations of nutrients and plant secondary compounds may lead to complementary relationships that enhance cattle performance and welfare. We determined whether grazing combinations of tanniferous legumes (Lotus corniculatus, birdsfoot trefoil [BFT], Onobrychis viciifolia, sainfoin [SF]), and alfalfa [ALF] (Medicago sativa) influence foraging behavior, performance, and hair cortisol concentration in beef cattle compared with grazing the same legumes as monocultures. Twenty-one pairs of heifers grazed three spatial replications of seven treatments: monocultures of BFT, SF, or ALF, and all possible two- and three-way choices among strips of these legumes: SF-BFT, ALF-BFT, ALF-SF, and ALF-SF-BFT in two periods of 25 d each (adaptation phase + experimental period) during two consecutive years. The lowest incidence of grazing events occurred in the BFT treatment (42.0% of the total scans recorded; P < 0.10), with the rest of the treatments ranging between 47.8% (SF-BFT) and 52.6% (ALF-SF) of the total scans recorded. Heifers selected a varied diet, preferring SF over BFT or ALF in a 46:27:27 ratio for the three-way choice, and in a 70:30 ratio for both two-way choices. Heifers preferred BFT over ALF (62:38 ratio) in a two-way choice. All treatments followed similar daily grazing patterns (P > 0.10), with two major grazing events (1 h after sunrise and 3 h before dark). No differences among treatments were observed for the number of steps taken by heifers on a daily basis, motion index, or the percentage of time heifers spent standing (1,599, 5,356, and 45.3%, respectively; P > 0.10), suggesting that heifers on choice treatments did not invest extra time in walking, searching, or patch switching activities relative to heifers grazing monocultures. Heifers grazing the three-way choice gained more body weight (1.27 kg/d) than the average gains observed for animals grazing in all legume monocultures (1.00 kg/d; P = 0.014) or two-way choices (0.97 kg/d; P = 0.007), suggesting a synergism among pasture species for the treatment with the highest diversity. No differences in hair cortisol concentration were observed among treatments, with values ranging between 1.4 (BFT) and 2.12 ng/g (three-way choice; P > 0.10). Thus, forage diversity has the potential to enhance animal performance without affecting grazing efficiency, likely explained by the spatial arrangement of the forage species presented in the study.

Preference for inorganic sources of magnesium and phosphorus in sheep as a function of need.

We determined whether sheep discriminate among different mineral supplements containing P and Mg and if they modify their selection as a function of the basal diet received. Forty lambs were offered four-way choices among inorganic sources of P and Mg: magnesium oxide in its coarse 1) C-MgO and granular 2) MgO forms and magnesium phosphate: 3) Mag33 (33% Mg and 2.7% P), and 4) MGP (25% Mg and 15% P), and two-way choices between MGP and each of the other minerals, and between MgO and C-MgO (baseline). Subsequently, lambs were randomly assigned to four groups (10 lambs/group) and fed rations such that the levels of Mg and P were low (LMg_LP), adequate (NMg_NP), low in Mg and adequate in P (LMg_NP), or adequate in Mg and low in P (NMg_LP). After 29 d, choice tests (post-deficiency) were repeated. During baseline, lambs ate and preferred Mag33 > C-MgO = MGP > MgO (P < 0.05). This pattern remained during post-deficiency tests, but lambs in LMg_LP and LMg_NP increased their preference for MGP and C-MgO, respectively, whereas lambs in NMg_LP increased their preference for C-MgO and MGP relative to baseline (P < 0.05). The serum concentrations of P and Mg increased after preference tests, and preference for MgO and MGP in low-Mg groups increased as the serum concentration of Mg declined (P < 0.05). Thus, lambs discriminated among different minerals and some groups modified their preferences based on the basal diets received, which rectified mineral imbalances.

The effect of plant bioactive compounds on lamb performance, intake, gastrointestinal parasite burdens, and lipid peroxidation in muscle.

Plant extracts have been widely used in animal production systems due to the benefits promoted by their bioactive components, mainly through their antioxidant effects and positive effects on animal growth, health, and meat quality. We determined whether bioactive compounds (BC) from grape (Vitis vinifera), olive (Olea europaea), and pomegranate (Punica granatum) have beneficial effects on lamb growth while controlling gastrointestinal parasitism and reducing skeletal lipid peroxidation in muscle. Fourteen lambs (4 to 5 mo of age) were housed in individual pens and assigned to two treatment groups (seven animals/group), where they received: 1) a basal diet of beet pulp:soybean meal (90:10) (CONTROL) and 2) the same diet, but containing 0.3% of BC extracted from grape, olive, and pomegranate (BNP). After 21 d of consuming their respective rations (period 1), all lambs were dosed with 10,000 L3 stage larvae of Haemonchus contortus. Intake, production, and physiological parameters were determined before infection (period 1), after oral dosage with L3 (period 2), and during early (period 3) and later (period 4) developmental stages of infection. Groups of animals did not differ in their ration intake or average daily gain, either before or after the infection, or in their parasitic burdens estimated through fecal egg counts (P > 0.05). Lambs under BNP showed greater feed efficiency before infection (P < 0.001), but the pattern reversed after infection. In addition, the inclusion of plant bioactives to the diet did not have an effect (P > 0.05) on blood or lipid peroxidation in muscle or on hemogram, serum concentration of haptoglobin, and immunoglobulin E. These results could be explained by low dietary doses and constrained absorption or ruminal inactivation of these compounds. Changes in feed efficiencies suggest a negative interaction between BC in the diet and parasitism, which warrants further research.

In vitro digestibility of mountain-grown irrigated perennial legume, grass and forb forages is influenced by elevated non-fibrous carbohydrates and plant secondary compounds.

BACKGROUND: Perennial legumes cultivated under irrigation in the Mountain West USA have non-fibrous carbohydrate (NFC) concentrations exceeding 400 g kg-1 , a level commonly found in concentrate-based ruminant diets. Our objective was to determine the influence of NFC concentration and plant secondary compounds on in vitro rumen digestion of grass, legume and forb forages compared with digestion of their isolated neutral detergent fiber (NDF) fraction. Forages were composited from ungrazed paddocks of rotationally stocked, irrigated monoculture pastures between May and August 2016, frozen in the field, freeze-dried, and ground. RESULTS: The maximum rate (RMax ) of gas production was greater for the legumes alfalfa (ALF; Medicago sativa L.) and birdsfoot trefoil (BFT; Lotus corniculatus L.) than for the legume cicer milkvetch (CMV; Astragalus cicer L.) the grass meadow brome (MBG; Bromus riparius Rehm.) and the non-legume forb small burnet (SMB; Sanguisorba minor Scop.), and intermediate for the legume sainfoin (SNF; Onobrychis viciifolia Scop.). The RMax of isolated NDF was greatest for BFT and CMV, intermediate for ALF, SNF and SMB and least for MBG. CONCLUSIONS: More than 900 g of organic matter kg-1 dry matter of legumes was digested after 96 h. Across forages, the extent of whole-plant digestion increased with NFC and crude protein concentrations, decreased with NDF concentrations, and was modulated by secondary compounds. The extent of digestion of isolated NDF decreased with concentration of lignin and residual tannins. © 2020 Society of Chemical Industry.

Use of biochar by sheep: impacts on diet selection, digestibility, and performance.

The objective of this study was to determine the influence of biochar obtained from exothermic production of lodgepole pine (Pinus contorta) and quaking aspen (Populus tremuloides) on sheep performance and diet digestibility and on preference for a ration enriched with this carbon-based material. Twenty-four lambs were housed in individual pens and assigned to one of three treatment groups (eight animals per group), where they received: 1) a 60:40 ration of alfalfa:barley (Control), 2) an isoenergetic and isonitrogenous ration with alfalfa, barley, and 2% biochar (BC), and 3) a simultaneous offer of the Control and BC rations (Choice). Lambs were exposed to two consecutive feeding periods (Period 1: 13 d and Period 2: 21 d), representing time intervals where the evolution of intake, animal performance, and rumen parameters were assessed; in vivo digestibility was determined during the last 5 d of the study. Ration intake did not differ among groups of lambs (P > 0.10), although during some days in Period 2, intake was greater for the BC and Choice groups than for the Control group (P < 0.05). Lambs in Choice had a lower preference for BC than for the Control ration (Period 1: P < 0.05; Period 2: P < 0.10), although they incorporated a substantial amount of BC (39 and 40%, for Periods 1 and 2, respectively) into their diets. No differences in body weight gains (ADG) or gain-to-feed ratios were found among groups of animals (P > 0.10), although dry matter digestibility and digestible dry matter intake was greater for lambs in the BC group than for lambs in Control group (P < 0.05). The ruminal concentration of the volatile acid acetate in Period 2 was greater for BC than for Choice (P < 0.05). During the same period, the concentration of valerate and ruminal pH values were greater in BC than in Control (P < 0.05). Thus, the addition of biochar to grain-based diets enhanced diet digestibility and influenced some ruminal parameters in lambs. Nevertheless, these positive effects were not reflected in significant improvements on ADG or feed conversion efficiencies. Lambs offered choices between Control and BC rations formed a diet with concentrations of biochar of ~1.2%, suggesting that these animals would tolerate such levels without reductions in ration palatability.

Preference for inorganic sources of calcium and phosphorus by sheep as a function of need.

We hypothesized that ruminants discriminate among different mineral supplements and modify their selection as a function of need. Forty lambs were offered four-way choices among P, Ca, and Mg sources: monosodium phosphate (MSP), Magnesium phosphate (MGP), Monocalcium phosphate (MCP), and Dicalcium phosphate (DCP); and two-way choices between DCP and the other mineral sources (Baseline). Subsequently, lambs were randomly assigned to four groups (10 lambs/group) and fed rations such that levels of Ca and P were low (LCa_LP), adequate (NCa_NP), low in Ca and adequate in P (LCa_NP), or adequate in Ca and low in P (NCa_LP). Four- and two-way choice tests were repeated (Post-deficiency). During Baseline, lambs ate and preferred MSP > MGP>DCP = MCP (p < .0001), showing that they discriminated among minerals. This pattern remained during four-way Post-deficiency tests, but lambs in LCa_LP, LCa_NP, and NCa_LP showed increased preference for MCP, MGP, and DCP, respectively, relative to other groups and Baseline (p < .05). Some mineral preference also changed in relation to serum concentration of P and Ca. Thus, lambs discriminated among minerals and some groups modified their preferences from Baseline to Post-deficiency choice tests, likely influenced by mineral needs, which in turn contributed to rectify mineral imbalances.

Grazing diverse combinations of tanniferous and non-tanniferous legumes: Implications for beef cattle performance and environmental impact.

We tested the effect of increasingly diverse combinations of tanniferous legumes (birdsfoot trefoil-BFT, sainfoin-SF) and alfalfa (ALF) on cattle performance, methane (CH4) emissions and nitrogen (N) balance. Pairs of heifers (401 ± 49.6 kg) grazed three spatial replications of 7 treatments (n = 3/treatment): monocultures (BFT, SF, ALF) and all possible 2- and 3-way choices among strips of these legumes in a completely randomized block design of two 15-d periods during 2 consecutive years. Average daily gains (ADG) of heifers grazing the tanniferous legumes (1.05 kg/d) were 40% greater (p < 0.10) than of heifers grazing ALF (0.74 kg/d) during the first year. Heifers grazing the 3-way choice had greater intakes (10.4 vs 7.8 kg/d; p = 0.064) and ADG (1.21 vs. 0.95 kg/d, p = 0.054) than those grazing monocultures, suggesting a nutritional synergism among legumes. The average CH4 emissions for legume monocultures vs. 2- and 3- way choices was 222 vs. 202 and 162 g/kg BW gain (p > 0.10), respectively. For heifers grazing SF and BFT compared with ALF, blood urea N was less (14.3 and 16.8 vs 20.8 mg/dL; p < 0.05) as were urinary N concentrations (3.7 and 3.5 vs 6.0 g/L; p < 0.05), but fecal N concentrations were greater (34.5 and 35.5 vs 30.5 g/kg, respectively; p < 0.05). Combining both tanniferous legumes (SF-BFT) led to the greatest declines in urinary N (2.24 g/L) and urea-N (1.71 g/L) concentration, suggesting that different types of tannins in different legumes result in associative effects that enhance N economy. In addition, heifers grazing 3-way choices partitioned less N into urine (40.7 vs 50.6%; p = 0.037) and retained more N (36.1 vs 25.2%, p = 0.046) than heifers grazing monocultures. In summary, combinations of tanniferous legumes with alfalfa improved animal performance and reduced environmental impacts relative to monocultures, resulting in a more sustainable approach to beef production in pasture-based finishing systems.

A Case for Eustress in Grazing Animals.

Herbivores grazing in extensive systems are exposed to a series of challenges, rooted in the inherent spatial and temporal variability of their environment that potentially constrain their health, nutrition, and welfare. Nevertheless, in this review, we argue that challenges induced by some biotic (e.g., vegetation) and abiotic (e.g., terrain) factors may also be viewed as "positive" sources of stress or eustress, since they present complex problems, that when solved successfully elicit a greater degree of behavioral plasticity and adaptability in grazing animals. Chemically and structurally diverse landscapes require animals to display complex behaviors and exhibit adaptive capabilities, like building a balanced and safe diet or finding shelter, which ultimately lead to positive emotional states. Thus, maintaining or enhancing the diversity occurring in natural systems represent a management approach that can be used to improve welfare and prepare the animal for an efficient adaptation to future, and potentially unknown, environmental challenges.

Tannin-containing legumes and forage diversity influence foraging behavior, diet digestibility, and nitrogen excretion by lambs1,2.

Diverse combinations of forages with different nutrient profiles and plant secondary compounds may improve intake and nutrient utilization by ruminants. We tested the influence of diverse dietary combinations of tannin- (sainfoin-Onobrichis viciifolia; birdsfoot trefoil-Lotus corniculatus) and non-tannin- (alfalfa-Medicago sativa L.) containing legumes on intake and diet digestibility in lambs. Freshly cut birdsfoot trefoil, alfalfa, and sainfoin were offered in ad libitum amounts to 42 lambs in individual pens assigned to 7 treatments (6 animals/treatment): 1) single forage species (sainfoin [SF], birdsfoot trefoil [BFT], and alfalfa [ALF]), 2) all possible 2-way choices of the 3 forage species (alfalfa-sainfoin [ALF-SF], alfalfa-birdsfoot trefoil [ALF-BFT], and sainfoin-birdsfoot trefoil [SF-BFT]), or 3) a choice of all 3 forages (alfalfa-sainfoin-birdsfoot trefoil [ALF-SF-BFT]). Dry matter intake (DMI) was greater in ALF than in BFT (P = 0.002), and DMI in SF tended to be greater than in BFT (P = 0.053). However, when alfalfa was offered in a choice with either of the tannin-containing legumes (ALF-SF; ALF-BFT), DMI did not differ from ALF, whereas DMI in SF-BFT did not differ from SF (P > 0.10). When lambs were allowed to choose between 2 or 3 legume species, DMI was greater (36.6 vs. 33.2 g/kg BW; P = 0.038) or tended to be greater (37.4 vs. 33.2 g/kg BW; P = 0.067) than when lambs were fed single species, respectively. Intake did not differ between 2- or 3-way choice treatments (P = 0.723). Lambs preferred alfalfa over the tannin-containing legumes in a 70:30 ratio for 2-way choices, and alfalfa > sainfoin > birdsfoot trefoil in a 53:33:14 ratio for the 3-way choice. In vivo digestibility (DMD) was SF > BFT (72.0% vs. 67.7%; P = 0.012) and DMD in BFT tended to be greater than in ALF (64.6%; P = 0.061). Nevertheless, when alfalfa was offered in a choice with either sainfoin or birdsfoot trefoil (ALF-SF; ALF-BFT), DMD was greater than ALF (P < 0.001 and P = 0.007, respectively), suggesting positive associative effects. The SF treatment had lower blood urea nitrogen and greater fecal N/N intake ratios than the ALF, BFT, or ALF-BFT treatments (P < 0.05), implying a shift in the site of N excretion from urine to feces. In conclusion, offering diverse combinations of legumes to sheep enhanced intake and diet digestibility relative to feeding single species, while allowing for the incorporation of beneficial bioactive compounds like condensed tannins into the diet.

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 ±â€¯0.042; P < 0.05) and intake of digestible energy (from 0.106 to 0.126 ±â€¯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.

Effect of tannin-containing hays on enteric methane emissions and nitrogen partitioning in beef cattle1.

The objective of this study was to determine whether feeding tannin-containing hays to heifers and mature beef cows influences enteric methane (CH4) emissions and nitrogen (N) excretion relative to feeding traditional legume and grass hays. Fifteen mature beef cows (Exp. 1) and 9 yearling heifers (Exp. 2) were each randomly assigned to treatment groups in an incomplete bock design with 2 periods and 6 types of hays with 3 hays fed each period (n = 5 cows and 3 heifers per treatment). Groups were fed tannin-containing [birdsfoot trefoil (BFT), sainfoin (SAN), small burnet (SML)] or non-tannin-containing [alfalfa (ALF), cicer milkvetch (CMV), meadow bromegrass (MB)] hays. Each period consisted of 14 d of adjustment followed by 5 d of sample collection. Nine cows and 9 heifers were selected for the measurement of enteric CH4 emissions (sulfur hexafluoride tracer gas technique), and excretion of feces and urine, while dry matter intake (DMI) was measured for all animals. The concentration of condensed tannins in SAN and BFT was 2.5 ± 0.50% and 0.6 ± 0.09% of dry matter (DM), respectively, while SML contained hydrolyzable tannins (4.5 ± 0.55% of DM). Cows and heifers fed tannin-containing hays excreted less urinary urea N (g/d; P < 0.001) and showed lower concentrations of blood urea N (mg/dL; P < 0.001) than animals fed ALF or CMV, indicating that tannins led to a shift in route of N excretion from urine to feces. Additionally, cows fed either BFT or CMV showed the greatest percentage of retained N (P < 0.001). Enteric CH4 yield (g/kg of DMI) from heifers (P = 0.089) was greatest for MB, while daily CH4 production (g/d) from heifers (P = 0.054) was least for SML. However, digestibility of crude protein was reduced for cows (P < 0.001) and heifers (P < 0.001) consuming SML. The results suggest that tannin-containing hays have the potential to reduce urinary urea N excretion, increase N retention, and reduce enteric CH4 emissions from beef cattle. The non-bloating tannin-free legume CMV may also reduce environmental impacts relative to ALF and MB hays by reducing N excretion in urine and increasing N retention.

Pasture chemoscapes and their ecological services.

Ruminant livestock-production systems are between a rock and a hard place; they are experiencing increasing societal pressure to reduce environmental impacts in a world that demands increased food supply. Recent improvements in the understanding of the nutritional ecology of livestock by scientists may help livestock producers respond to these seemingly contradictory demands. Forages are nutrition and pharmacy centers with primary (nutrients) and plant secondary compounds (PSC; pharmaceuticals, nutraceuticals), which can provide multiple services for the proper functioning of agroecosystems. Legumes with lower contents of fiber and higher contents of nonstructural carbohydrates, coupled with different types and concentrations of PSC (e.g., condensed tannins, terpenes), create a diverse array of chemicals in the landscape (i.e., the "chemoscape") with the potential to enhance livestock nutrition, health and welfare relative to foodscapes dominated by grasses and other conventional feeds. These PSC-containing plants may reduce methane emissions and nitrogen (N) excretion from animals while increasing animal growth rate compared with swards dominated by grasses, and provide meat quality that appeals to consumers. Condensed tannins from sainfoin and saponins from alfalfa and manure of cattle consuming these forages also reduce N mobilization in soils, reduce nutrient leaching, and increase plant-available N stores for future use. The challenge for future pastoral production systems is to design multifunctional spatiotemporal arrangements of forages with "ideal" chemical diversity for specific ecoregions, aiming to achieve sustainability while increasing production goals and improving ecosystem services. Thus, the objective of this review is to stimulate the quest for chemically and taxonomically diverse pastoral feeding systems that optimize overall productivity; reduce environmental impacts; and enhance livestock, soil, and human health.

Self-selection of plant bioactive compounds by sheep in response to challenge infection with Haemonchus contortus.

Plant bioactives can potentially benefit herbivores through their effects on health and nutrition. The objective of this study was to determine the importance of polyphenols and terpenes on the ability of lambs to self-select these compounds when challenged by a parasitic infection and the subsequent impact on their health and productivity. Thirty-five lambs were housed in individual pens and assigned to five treatment groups (7 animals/group), where they received: 1) A basal diet of beet pulp:soybean meal (90:10) (CONTROL); 2) The same diet, but containing 0.3% of bioactive natural plant compounds extracted from grape, olive and pomegranate (BNP); 3) A simultaneous offer of the diets offered to the Control and BNP groups (Choice-Parasitized; CHP-1); 4) The Control diet, and when lambs developed a parasitic infection, the choice described for CHP-1 (CHP-2); and 5) The same choice as CHP-1, but animals did not experience a parasitic burden (Choice-Non-Parasitized; CHNP). Lambs, except CHNP, were dosed with 10,000 L3 stage larvae of Haemonchus contortus. Infected lambs under choice treatments (CHP-1 and CHP-2) modified their feeding behavior in relation to the CHNP group as they increased their preference for the feed containing polyphenols and terpenes, interpreted as a behavior aimed at increasing the likelihood of encountering medicinal compounds and nutrients in the environment that restore health. This change in behavior corresponded with an improvement in feed conversion efficiency. However, an increased preference for the diet with added plant bioactives did not have an effect on parasitic burdens, hematological parameters, blood oxidation, or serum concentration of IgE.

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.

Plant Community Chemical Composition Influences Trembling Aspen (Populus tremuloides) Intake by Sheep.

Nutrients and plant secondary compounds in aspen (Populus tremuloides) may interact with nutrients in the surrounding vegetation to influence aspen use by herbivores. Thus, this study aimed to determine aspen intake and preference by sheep in response to supplementary nutrients or plant secondary compounds (PSC) present in aspen trees. Thirty-two lambs were randomly assigned to one of four molasses-based supplementary feeds to a basal diet of tall fescue hay (N = 8) during three experiments. The supplements were as follows: (1) high-protein (60% canola meal), (2) a PSC (6% quebracho tannins), (3) 25% aspen bark, and (4) control (100% molasses). Supplements were fed from 0700 to 0900, then lambs were fed fresh aspen leaves collected from stands containing high (Experiment 1, 2) or low (Experiment 3) concentrations of phenolic glycosides (PG). In Experiment 2, lambs were simultaneously offered aspen, a forb (Lathyrus pauciflorus), and a grass (Bromus inermis) collected from the aspen understory. Animals supplemented with high protein or tannins showed greater intake of aspen leaves than animals supplemented with bark or the control diet (P < 0.05), likely because some condensed tannins have a positive effect on protein nutrition and protein aids in PSC detoxification. Overall, animals supplemented with bark showed the lowest aspen intake, suggesting PSC in bark and aspen leaves had additive inhibitory effects on intake. In summary, these results suggest that not only the concentration but also the types and proportions of nutrients and chemical defenses available in the plant community influence aspen use by herbivores.

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.

Free availability of high-energy foods led to energy over-ingestion and protein under-ingestion in choice-fed broilers.

The objective of this study was to compare energy and protein content of the diet selected by choice-fed broilers with that of broilers fed a balanced diet. One hundred and eighty 1-day-old male broilers were randomly assigned in groups of 10 to one of three experimental treatments (n = 6). Control broilers were fed a standard balanced diet, whereas choice-fed broilers were fed three foods which were more concentrated (Choice C+ treatment) or less concentrated (Choice C- treatment) in protein, carbohydrate or fat. We evaluated food intake behavior, nutrient intake, and performance parameters of broilers from 2 to 7 weeks of age. Choice C+ broilers showed enhanced preference for the high-fat food, which led to higher energy intake and lower protein intake than those of control broilers at 2 to 4 weeks of age. Body weight, weight gain and feed conversion efficiency were negatively affected by diet selection of Choice C+ broilers. Choice C- broilers selected a balanced diet, and showed performance parameters similar to those of control broilers. Our results supported the hypothesis that free availability of high-energy foods bias ingestive behavior of choice-fed broilers toward selecting a diet with higher energy and lower protein than needed for normal growth.

Aspen (Populus tremuloides Michx.) intake and preference by mammalian herbivores: the role of plant secondary compounds and nutritional context.

Aspen (Populus tremuloides Michx.) has evolved a chemical defense system comprised of phenolic glycosides (PG), which effectively deter insect herbivory. However, much less is known about the role of PG and the nutritional quality of the associated plant community on aspen browse susceptibility to mammalian herbivores. In three successive periods during the growing season, we conducted experiments with sheep by offering leaves from two aspen stands with different concentrations of PG (LOW, HIGH) or aspen leaves vs. leaves from a forb (Utah pea, Lathyrus pauciflorus) or a grass (smooth brome, Bromus inermis Leyss.) growing in an aspen understory. Intake of aspen (19 to 35 % PG) was low in all periods (1 to 6 g/Kg(0.75) in 2 hr) supporting the notion that aspen's defense system may contribute to its ecological success. However, lambs ate larger amounts of LOW than of HIGH suggesting that sheep could discriminate between aspen stands with different concentrations of PG, even when both stands were relatively well defended. Concentration of nutrients and chemical defenses in aspen leaves remained fairly stable across the growing season, and preference for aspen increased over the growing season. In contrast, preference for the forb and the grass decreased across the growing season in concert with a decline in the nutritional quality of these plants. The data suggest that nutritional context of aspen and associated forage species drove preference more than contrasts in defense chemistry of aspen. There may be periods of "susceptibility" of aspen use by mammalian herbivores, despite high concentrations of chemical defenses, which can potentially be targeted by management to reduce aspen herbivory.