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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.

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.

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.

Forages can provide a complete diet for ruminant animals, increasing the sustainability of beef production systems worldwide while reducing competition with humans for agricultural land or grain crops. Much of the emphasis on the nutritional characteristics of forages has been on the fiber, sugars, starch, and protein they supply to the rumen, despite the fact that other less-explored constituents, i.e., neutral detergent soluble fiber (NDSF) and other non-structural or non-fiber carbohydrates (NFC) also play a key role in the nutrition of ruminants. This paper explores the less investigated potential of temperate legumes to accumulate levels of NFC comparable to corn silage or beet pulp in cool, dry environments under irrigation, and its implications for forage-based beef production systems. We conclude that genetic or managerial interventions (i.e., breeding programs, defoliation frequency) or ecological conditions (i.e., climate, elevation) that increase concentrations of NFC in legumes can enhance beef production, meat quality, and the efficiency of nitrogen utilization by ruminants while reducing environmental impacts.

Incorporation of legumes into forage systems has been a widely adopted strategy to increase pasture productivity and forage nutritive value, while reducing N inputs. In addition, some legumes contain beneficial chemicals like condensed tannins (CT), which could enhance the efficiency of energy and protein use in ruminants relative to other forages. We assessed (i) animal performance, (ii) methane emissions (SF6 technique), and (iii) concentration of nitrogen in urine and blood in cattle grazing a CT-containing legume (birdsfoot trefoil; BFT), a legume without tannins (cicer milkvetch; CMV), a grass (meadow brome; MB), or in cattle fed a total mixed ration (TMR). Fifteen Angus heifers were randomly assigned to one of three treatment pastures: (1) BFT, (2) CMV, and (3) MB. Each treatment had 5 spatial replications, randomly divided into three paddocks (64 × 57m), seeded with BFT, CMV or MB, and one heifer was assigned to each paddock. Five Angus heifers were randomly assigned to individual adjacent pens and received a TMR ration (25% of alfalfa hay, 25% corn silage and 50% chopped barley) during the same period. Response variables were analyzed as a split-plot design, with experimental units as the random factor and treatment as a fixed factor with day as the repeated measure. Cows grazing BFT (1.9% condensed tannins) or fed the TMR showed greater weight gains than cows grazing CMV or MB (P = 0.0006). Methane emissions did not differ among treatments (P > 0.05; Table 1). Blood urea nitrogen concentrations were similar in cows grazing BFT or CMV (P = 0.1202), but greater than in animals grazing MB or fed TMR (P < .0001). Urinary nitrogen concentrations were similar among treatments (P = 0.5266). These results suggest grazing tanniferous legumes enhanced BW gains with similar methane and urinary nitrogen emissions to grass and confinement alternatives and greater levels of production than grass or CMV.

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.

Our objective was to explore diet selection and productive performance by sheep during peripartum. Pregnant Saint-Croix and Katahdin ewes were housed in individual pens from 100 days of gestation to 60 days of lactation and assigned to two groups: Free-choice-FC and Mixed-ration-MR (n = 12/group). Sheep in FC received ad-libitum amounts of soybean meal, sorghum grain, alfalfa and oat hays, presented in individual troughs. Animals in MR received a total-mixed-ration with these feeds, balanced for gestation or lactation according to NRC. Dry matter (and nutrient) intake/kg BW was measured daily, whereas BW and BCS were measured every 7 and 14 d, respectively. Data was analyzed as a Linear Mixed Model with repeated measures; group, breed, litter size (single, twins) and parity (primiparous, multiparous) were the fixed factors and sheep (random factor) was nested within group. Overall dry matter and ME intake did not differ between groups (P > 0.05), without breed, litter size or parity effects (P > 0.05), but protein intake was greater and NDF and ADF intakes were lower in FC than in MR (P < 0.001). During gestation, FC sheep consumed soy=alfalfa >sorghum >oats, and during lactation they increased (2X) soy intake (P < 0.001). Body weight was similar between groups (73.3±1.3, and 70.6±1.3 kg, for FC and MR, respectively; P=0.148), whereas BCS was greater for FC than for MR (3.9±0.2 vs. 3.3 ±0.1; P = 0.01). During lactation, ewe BW (67.3±1.3 vs. 61.92±1.3 kg; P = 0.01) and BCS (3.83±0.1 vs. 3.03±0.1; P < 0.001) were greater for FC than for MR. Offspring BW was similar between groups (11.5±0.6, and 11.4±0.5 kg, for FC and MR, respectively; P = 0.804). In conclusion, the free-choice treatment enhanced ewe nutrition, reducing BW and BCS losses during lactation without influencing offspring growth. Free-choice may enable ewes to meet their individual nutrient needs, with benefits to their welfare and postpartum ovarian activity.

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 legume species 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.

The objective of this study was to explore the influence of prior dietary experiences on intake and selection of novel feeds by lambs. Twenty lambs housed in individual pens were assigned to two groups (10lambs/group): Negative (NE) and Positive (PE) Experiences, in a split-plot design. Lambs were offered a nutritive novel feed followed by intra-ruminal infusions of lithium chloride-LiCl (150 mg/kg BW), a toxicant that causes food aversions (NE), or vehicle (water; PE). The feed was offered daily and infusions were delivered only when intake was ≥50g, when the protocol was repeated with another novel feed until 4 feeds (oats, wheat bran, corn, beep pulp) were offered. After exposure, all lambs were tested for their acceptance of single novel feeds, each offered during 2 consecutive days: sorghum grain, rice bran, Calfmanna® pellets and soybean meal. Subsequently, all lambs were offered a 5-way choice among these feeds and alfalfa (familiar feed). Intake data, preference and Shannon’s diversity index (5-way choices) were analyzed with a Mann-Whiney U test. During exposure, the NE group ate less of the 4 feeds than the PE group (P < 0.05). Moreover, as exposure progressed, it took more days for NE lambs to reach the 50 g intake threshold, suggesting that neophobia in this group increased with negative experiences. During testing, NE lambs ate less (P < 0.05) of the novel feeds, except soybean meal, than the PE lambs. During the 5-way-choice test, preference for alfalfa was 63.6±3.5% for NE and 45.2±2.6% for PE (P < 0.001). The Shannon’s index was 0.85±0.05 for NE and 1.24±0.03 for PE (P < 0.001), suggesting that lambs in NE selected a less diverse diet. Thus, prior experience influenced neophobia and dietary diversity, an outcome that could impact the nutrition and welfare of grazing animals introduced to novel environments and the diversity of plant communities.

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.

Pasture-based production systems represent a significant sustainable supplier of animal source foods worldwide. For such systems, mounting evidence highlights the importance of plant diversity on the proper functioning of soils, plants and animals. A diversity of forages and biochemicals –primary and secondary compounds- at appropriate doses and sequences of ingestion, may lead to benefits to the animal and their environment that are greater than grazing monocultures and the isolated effects of single chemicals. Here we review the importance of plant and phytochemical diversity on animal nutrition, welfare, health, and environmental impact while exploring some novel ideas about pasture design and management based on the biochemical complexity of traditional and non-traditional forage sources. Such effort will require an integration and synthesis on the morphology, ecophysiology, and biochemistry of traditional and non-traditional forage species, as well as on the foraging behavior of livestock grazing diverse pasturelands. Thus, the challenge ahead entails selecting the “right” species combination, spatial aggregation, distribution and management of the forage resource such that productivity and stability of plant communities and ecological services provided by grazing are enhanced. We conclude that there is strong experimental support for replacing simple traditional agricultural pastures of reduced phytochemical diversity with multiple arrays of complementary forage species that enable ruminants to select a diet in benefit of their nutrition, health and welfare, whilst reducing the negative environmental impacts caused by livestock production systems. Fil: Distel, Roberto Alejandro. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina Fil: Arroquy, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Buenos Aires Sur. Estacion Experimental Agropecuaria Cesareo Naredo.; Argentina Fil: Lagrange, Sebastián. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Bordenave; Argentina. State University of Utah; Estados Unidos Fil: Villalba, Juan Jose. State University of Utah; Estados Unidos

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.

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.

We determined whether sheep discriminate among mineral supplements containing P and Mg and if they modify their selection as a function of need. During 3 consecutive days, 40 lambs under a basal diet of alfalfa pellets and barley grain were offered 4-way choices among= (1) MgO-powder form (MgO-82% Mg), (2)MgO-coarse form (C-MgO-82% Mg), (3) Magnesium Phosphate (Bolifor® Mag33-33% Mg, 2.7% P), and (4)Magnesium Phosphate (Bolifor® MGP-25% Mg, 15% P), and 2-way choices between MGP and each of the other minerals, and between MgO and C-MgO (Baseline). Subsequently, lambs were randomly assigned to 4 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, groups received again the described choices (post-deficiency). Intake and preference indexes during choice tests were analyzed as a split-plot design with lambs nested within group and day as the repeated measure. During Baseline, lambs ate and preferred Mag33 > C-MgO = MGP > MgO (P < 0.05). This pattern remained during post-deficiency, but lambs in LMg showed the greatest preference for Mag33 (P < 0.05). All lambs preferred C-MgO over MgO or MGP (P < 0.05), but lambs in LMg-NP showed the greatest preference for C-MgO (P < 0.05) and the lowest preference for MGP (P < 0.05). Serum concentrations of P (7.1 to 8.4±0.2 mg/dL) and Mg (3.0 to 3.9±0.1 mg/dL) increased after post-deficiency tests relative to Baseline (P < 0.05). Lambs discriminated among different mineral sources and the physical form of MgO influenced preference. Groups in low Mg diets favored sources of Mg with no or low concentration of P, and when P was adequate (LMg-NP), they reduced their preference for the source with the greatest concentration of P (MGP).

The low intake of medusahead grass (Taeniatherum caput-medusae ssp. asperum) by sheep is attributed to the high silica content of the plant and its negative impact on digestibility, making this weed a successful competitor in grazed plant communities. The goals of this study were to determine the influence of (1) plant maturity stage (from late vegetative stage to beginning of senescence and thatch), (2) particle size (1, 5, 10 and 20 mm), and (3) high-quality feeds (alfalfa hay and a high-energy concentrate) on fermentation kinetics and apparent digestibility of medusahead relative to palatable feeds (alfalfa and tall fescue hays, and high-energy concentrates). In vitro gas production was estimated and apparent digestible organic matter (DOM) of the substrates was assessed after incubation. Medusahead from late vegetative to senescence stage had greater DOM (65% to 71%; P0.05), and lower than the high-energy concentrates assayed (77% to 79%; P0.05) on digestibility parameters were observed by the addition of high-quality feeds to medusahead. Slow fermentation kinetics and a significant inhibitory effect of particle size on apparent digestibility of organic matter contribute to explain the low use of medusahead by sheep. Such inhibitory effect may also underlie the lack of positive associative effects observed during the study.

We determined whether lambs discriminate among mineral supplements containing P and Ca and if they modify their choices as a function of need. During 3 consecutive days, 40 lambs under a basal diet of alfalfa pellets and barley were offered 4-way choices among= (1) Bolifor® Monosodium phosphate (MSP-24% P), (2) Bolifor® Magnesium phosphate (MGP-15% P, 25% Mg), (3) Bolifor® Monocalcium phosphate (MCP-22.7% P, 16.5% Ca) and (4) Dicalcium phosphate (DCP-18.5%P, 23% Ca), and 2-way choices between DCP and each of the remaining minerals (Baseline). Subsequently, lambs were randomly assigned to four groups (10 lambs/group) and fed beet pulp-based basal rations such that the 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). After 60 d, groups had the described 4- and 2-way choices (Post-deficiency). Intake and preference indexes during choice tests were analyzed as a split-plot design with lambs nested within group and day as the repeated measure. During Baseline, lambs ate and preferred MSP > MGP > DCP = MCP (P < 0.0001). This pattern remained during post-deficiency, but in contrast to Baseline, lambs in NCa-LP, LCa-NP, and LCa-LP showed the greatest preferences for MSP (42%), MGP (42%) and MCP (22%), respectively (SEM = 4%; P < 0.05). Groups under LCa in 2-way choices showed greater preference for MCP (56%) than groups under NCa (39%; SEM = 5%; P < 0.05), and lambs in LCa-NP revealed the greatest preference for MGP (64%; SEM = 6%; P < 0.05). Serum P concentration after post-deficiency choice tests (9.7 ± 0.7 mg/dL) returned to Baseline values, but Ca concentration was 0.9 mg/dL lower (9.3 ± 0.3 mg/dL; P < 0.05) than in Baseline. Thus, lambs discriminated among mineral sources and displayed preferences reflecting their needs.

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 L3 Haemonchus 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 rations of high energy (HE) or high protein (HP) density. The other groups received the same choice, but QT were added (4%) to HE (Group 2), to HP (Group 3) or to both HE and HP (Group 4). Intake and preference indexes were analyzed as a split-plot design with lambs nested within group and day as the repeated measure. All groups increased their preference for HE when parasitized relative to Phase 1 (0.66 and 0.44 ± 0.042, respectively; P < 0.05). As a result, lambs increased their intake of digestible energy during Phase 2 (0.126 ± 0.007 Mcal/kg BW) relative to Phase 1 (0.106 ± 0.007 Mcal/kg BW; P < 0.05). These patterns remained during Phase 3. Only lambs receiving QT in the HE increased their intake of condensed tannins from Phase 1 to Phase 2 (P < 0.05). Fecal egg counts (FEC) 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 parasitized lambs prioritized the ingestion of energy-dense over protein-dense foods or medicinal condensed tannins. Nevertheless, intake of tannins increased when these compounds were present in the energy-dense food, suggesting that selection of condensed tannins was influenced by the nutritional composition of the foods during testing.

Tannin-containing legumes like birdsfoot trefoil (BFT) and sainfoin (SAIN) may enhance the efficiency of energy and protein use in ruminants relative to grasses and other legumes such as alfalfa (ALF). In addition, synergisms among diverse combinations of forages may further contribute to improve the efficiency of nutrient utilization, approaching values attained by feeding grain-based rations in confinement. We tested the effects of grazing monocultures of (1) ALF, (2) BFT, (3) SAIN or (4) a three-way choice of these legumes on cattle performance, intake and methane emissions. Twelve pairs of heifers (366 ± 46.2 kg) grazed three spatial replications of the aforementioned four treatments in a completely randomized block design. Animals grazed during 2 periods of 22-d each and composited forage and fecal samples were collected during five consecutive days at the end of each period to estimate apparent digestibility, using ADL as an internal marker. Fecal output was measured using an external marker (Cr2O3) dosed once a day for 9 days. Fecal output along with digestibility data were used to estimate dry matter intake (DMI). Methane emissions were assessed using the sulfur hexafluoride technique during each 5-d collection period. Results were analyzed as a completely randomized block design with spatial replication (random effect) nested within treatments, and day and period as the repeated measures. Heifers grazing the three-way choice showed greater DMI and ADG than animals grazing monocultures (P < 0.10; Table 1), suggesting a synergism among pastures. In addition, g methane emissions/kg of gain tended to be lower (14 to 24% range) for the three-way choice than for monocultures (pre-planned contrast three-way choice vs. monocultures; P = 0.12; Table 1). In summary, combinations of tannin-containing legumes and alfalfa yielded the compounded benefits of improved animal gains and reduced environmental impacts per kg of BW gain. [Image: see text]

Plant bioactives can potentially benefit herbivores through their effects on health and nutrition. The objective of this study was to determine the importance of antioxidant 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 (AOX); 3) A simultaneous offer of the diets offered to the Control and AOX 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. Results were analyzed as a completely randomized design with seven replications per treatment. Individual animal was considered the experimental unit. 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 (P < 0.05), 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 (P < 0.05). 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.

Grazing-based livestock-production systems are between a rock and a hard place— where they experience increasing societal pressures to reduce environmental impacts in a world that demands increased and sustained productivity. Recent advances in understanding the nutritional ecology of herbivores may contribute to alleviate these seemingly contradictory endeavors. Forages are nutrition centers and pharmacies with vast arrays of primary (nutrients) and secondary (pharmaceuticals, nutraceuticals) compounds (PSC), which can provide multiple services vital for agroecosystems. Legumes with different types and concentrations of cell walls and with high concentrations of cell contents (e.g., birdsfoot trefoil, sainfoin, cicer milkvetch), coupled with different types and concentrations of PSC (e.g., hydrolizable and condensed tannins, terpenes) create a diverse foodscape with potential to enhance livestock nutrition, health and welfare relative to grasses, other legumes or pasture monocultures. In the process, livestock learn to forage these PSC-containing plants and their combinations, leading to reductions in methane and nitrogen emissions and to improvements in meat quality. Condensed tannins from sainfoin and saponins from alfalfa and from manure of cattle consuming these forages also reduce nitrogen mobilization in soils, reducing leaching and increasing plant-available nitrogen stores for future use. The challenge for future grazing-based livestock-production systems entails the provision of the “ideal” chemically diverse forages for a specific ecoregion in optimal temporal and spatial scales and sequences such that sustainability is achieved without compromising the ability to meet the production levels and ecological services described above.

Medusahead [ (L.) Nevski] has become a major invasive plant on the annual grass-dominated rangelands within the Channeled Scablands of eastern Washington. Livestock typically avoid grazing medusahead, and forage alternatives are becoming limited in the region. Our hypothesis was that supplying a high-CP supplement would provide a nutritional context that complements the nutritional composition of medusahead and other annual grasses and thus aid cattle in utilizing this vegetation component, making grazing a more effective method of weed control. Cattle grazed annual grass-infested rangelands dominated with medusahead for 10-d periods during June, July, and August over 2 consecutive years. Eight separate pastures were grazed by cattle pairs during each of the 3 grazing periods. Cattle in 4 control pastures received no supplement and cattle in another 4 pastures received a supplement of canola meal that supplied 75% of the daily recommended CP requirement. Bite counts were used to determine diet composition. Forage categories consisted of annual grasses, perennial grasses, and forbs. Bites taken of annual grasses were similar between treatment groups during the first 5 d of the grazing period ( > 0.05), and then cattle supplemented with canola meal increased consumption of annual grasses, during d 6 to 10 of the grazing periods, over nonsupplemented animals ( 0.05). Forb production was greatest the first year of grazing and declined the second year of grazing and continued to decline the following year with no grazing ( < 0.05). Perennial grass production was low throughout the study. The effects of grazing on medusahead abundance suggest cattle may be used to graze this weed after it has matured in an integrated management program with other forms of control to reduce infestation prior to seeding with desirable forage species.

It was hypothesized that a tannin-rich legume such as sainfoin attenuates the negative postingestive effects of ergot alkaloids in tall fescue. Thirty-two 4-mo-old lambs were individually penned and randomly assigned to a 2 × 2 factorial arrangement with 2 legume species, sainfoin (SAN; 2.9% condensed tannins) or cicer milkvetch (CIC; without tannins) and a mixed ration containing tall fescue seed (50:30:20 seed:beet pulp:alfalfa) with 2 levels of endophyte infection (endophyte-infected tall fescue seed [E+; 3,150 ug/L ergovaline] or endophyte-free tall fescue seed [E-]). For a 10-d baseline period, half of the lambs were fed SAN and half were fed CIC and all lambs had ad libitum amounts of E-. In an ensuing 10-d experimental period, the protocol was the same except half of the lambs fed SAN or CIC received E+ instead of E-. Subsequently, all lambs could choose between their respective legume and seed-containing ration and between E+ and E-. Finally, an in vitro radial diffusion assay was conducted to determine whether tannins isolated from SAN would bind to alkaloids isolated from E+. All groups consumed similar amounts of E- during baseline period ( > 0.10), but lambs ate more E- than E+ during the experimental period ( 0.10), but lambs fed E+ had lower rectal temperatures per gram of feed ingested when supplemented with SAN than with CIC ( 0.10). All lambs preferred their treatment ration over their treatment legume, but lambs in the SAN and E+ treatment ate more legume + ration than lambs in the CIC and E+ (CIC-E+; < 0.05) treatment. All lambs preferred E- over E+, but lambs in the CIC-E+ treatment ate the least amount of E+ ( < 0.05). Binding of isolated SAN tannins to protein was reduced by the E+ isolate ( < 0.05), suggesting a tannin-alkaloid complexation but only from tannins extracted from SAN fed early in the experimental period. In summary, SAN supplementation increased intake of and preference for E+ and reduced rectal temperatures relative to CIC supplementation. Our results suggest that these effects were mediated by the condensed tannins in SAN through alkaloid inactivation, an interaction that declined with plant maturity.

The goal of this study was to determine DM (DDM) and organic matter (DOM) digestibility and fermentation kinetics of six hays and their isolated NDF fractions using the in vitro gas production method. Alfalfa (ALF), birdsfoot trefoil (BFT), cicer milkvetch (CMV), sainfoin (SF) (all legumes), meadow bromegrass (MB) and small burnet (SB) substrates were incubated with beef cow rumen fluid for 96 h, and gas production kinetics was adjusted using a single phasic model with three parameters. The fermentation was replicated four times (runs) using triplicate samples. Results were analyzed as a randomized block two-way analysis of variance with type of sample (hay, NDF isolate) and species as the main factors and runs as blocks. For unfractionated hays, the asymptotic cumulative gas production (parameter A) was greatest for the grass (MB) and for NDF, MB was greater than ALF and CMV (P0.10), suggesting the absence of cell solubles required a shift in rumen microbial ecology. In conclusion, grass hay is more completely digested than the legume hays and forb, but the slower rate of digestion of the grass predicts lower voluntary intake for grass hay than for legume or forb hays. An absence of plant secondary compounds may explain the slower rates of digestion of other legumes compared with ALF. [Image: see text]

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.

We determined if combinations of adjacent pastures of 3 forage species led to complementary relationships that influenced animal behavior and performance over monocultures. Grazing bouts, behavioral levels of activity, blood urea N (BUN), chemical composition of feces, BW, and herbage biomass before and after grazing were monitored when beef calves strip-grazed 3 replications of 4 treatments from June 14 through August 23, 2013 (9 animals/treatment). Animals grazed monocultures of: 1) tall fescue (TF), 2) alfalfa (ALF), 3) sainfoin (SAN), or 4) a choice of strips of forages TF, ALF, and SAN (CHOICE). The lowest and greatest incidence of foraging bouts occurred for cattle in CHOICE and SAN, respectively (P ALF > TF (P < 0.01). Animals on TF and CHOICE took greater number of steps than animals grazing a monocultures of either legume (P = 0.01). Calves in TF had lower BUN (P < 0.01) and fecal CP concentration (P < 0.01) than calves grazing the remaining treatments, whereas animals in SAN showed the greatest concentrations of fecal CP (P < 0.01). Fecal NDF concentration was the greatest for animals grazing TF and the lowest for animals grazing SAN (P < 0.01), whereas fecal ADF concentration was greater for animals grazing TF and SAN than for animals grazing CHOICE and ALF (P = 0.02). Calcium, Mg, and Zn concentrations were the lowest in feces from calves grazing TF and the greatest for calves grazing a monoculture of either legume (P < 0.05). When averaging both periods, animals grazing SAN, ALF, or CHOICE gained more BW than animals grazing TF (P < 0.01). Thus, calves in CHOICE incorporated tall fescue into their diets, were more active, and displayed a lower number of grazing bouts than calves grazing monoculture of either legume. Herbage diversity may lead to levels of ADG comparable to legume monocultures with the potential benefit of maintaining plant species diversity in pasturelands.

We determined if tall fescue in a mixture with either tannin-containing sainfoin or saponin-con- taining alfalfa affected cattle foraging behavior, perfor- mance, 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 Septem- ber 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). No incidences of bloat were detected. When cattle (3 calves/treatment in 2010 and 8 calves/treatment in 2012) were slaugh- tered 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). 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.

Lambs were assigned to four groups of seven and treated as follows for 12 days: control group (BP) was fed beet pulp; group T (tannin remedy) received the BP diet including 80 g/kg of quebracho extract; group S (saponin remedy) received the BP diet including 15 g/kg of quillaja extract; and group C had a free choice between T and S remedies. Lipid oxidation was lower in meat from S lambs compared to T lambs (P

Tannins in sainfoin (Onobrychis viciifolia) may bind to alkaloids in endophyte-infected tall fescue [E+; Lolium arundinaceum (Schreb.) Darbysh.] and attenuate toxicosis. If so, supplementing E+ with sainfoin will increase use of E+ by sheep, and polyethylene glycol (PEG)-a polymer that selectively binds to tannins-will reduce such response. To test these predictions, thirty-six 2-mo-old lambs were randomly assigned to 3 treatments (12 lambs/treatment). During exposure, all lambs were individually penned and fed E+ supplemented with beet pulp (CTRL), fresh-cut sainfoin and beet pulp (SAIN), or fresh-cut sainfoin plus PEG mixed in beet pulp (SAIN+PEG). Feed intake was measured daily. Rectal temperatures and jugular blood samples were taken at the beginning and end of exposure. After exposure, all lambs were offered choices between endophyte-free tall fescue (E-) and orchardgrass, and preference for E- was assessed. Then, all lambs were allowed to graze a choice of E+ and sainfoin or a monoculture of E+. The foraging behavior of lambs was recorded. When sainfoin was in mid-vegetative stage, lambs in SAIN ingested more E+ than lambs in CTRL (P = 0.05), but no differences were detected between lambs in SAIN+PEG and CTRL (P = 0.12). Sainfoin supplementation improved some physiological parameters indicative of fescue toxicosis. Lambs in SAIN had lower rectal temperatures (P = 0.02), greater numbers of leukocytes (P 0.05). On the other hand, when they grazed on a monoculture of E+, lambs in SAIN+PEG showed greater acceptance of E+ than lambs in SAIN or in CTRL (P < 0.05). In summary, sainfoin supplementation alleviated several of the classic signs of fescue toxicosis and increased intake of endophyte-infected tall fescue. Tannins in sainfoin partially accounted for this benefit since feeding a polymer that selectively binds to tannins (PEG) attenuated some these responses. However, sainfoin supplementation during initial exposure to E+ did not lead to an increased preference for E+ during grazing.

Glyphosate-treated medusahead (Taeniantherum caput-medusae (L.) Nevski) has been shown to increase livestock grazing preference for an otherwise unpalatable plant. This response could be the consequence of changes in the plant’s digestion kinetics induced by the herbicide. Thus, the objective of this study was to determine the in vitro digestion kinetics of medusahead treated with different herbicide concentrations (788 g ae/ha(-1) (High), 394 g ae/ha(-1) (Low), and 0 g ae/ha(-1) (Control)) at different particle lengths (1, 20, 30, and 40 mm). Medusahead was treated with glyphosate during the late vegetative to early reproductive stage of the plant at two locations, Mantua, UT and Ritzville, WA. In vitro gas production was measured at 2, 4, 6, 8, 12, 18, 24, 36, 48, 72, 96, and 120 h of incubation, and gas production kinetics was adjusted using a single phasic model with three parameters. Apparent digestible organic matter (DOM) and ash content of the substrates were also measured after incubation. The experimental design was a completely randomized block design with herbicide treatment, particle length and location as fixed factors and four runs as replicates. The smallest particle length, Low herbicide treatment and Ritzville location showed the greatest DOM and lowest Ash content (Table 1; P

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

Experiences early in life influence preferences for the forages which animals eat as adults, but little is known about how such experiences affect forage intake and digestibility. We hypothesized that experience with high fiber (HF) diets in utero enables cattle to better utilize HF diets by enhancing intake and digestibility of HF diets. We exposed cows to either HF or low fiber (LF) diets from October 20 until parturition on March 15. The HF diet was primarily ammoniated wheat straw (AWS), while the LF diet was mainly grass hay (700 g/kg orchardgrass and 300 g/kg meadow bromegrass). The two diets were iso-net energy (NEm), isonitrogenous, and similar in mineral and vitamin contents, but they varied 10-fold in neutral detergent soluble carbohydrates. Following weaning, the 8 mo old calves from mothers fed HF or LF diets during pregnancy were fed AWS and a high fiber supplement, and dry matter (DM) intake and digestibility were measured during the last half of a 40 d experiment (i.e., 26 d adaptation, 14 d measured DM intake, 5 d measured DM digestibility). Intake (5.6 versus 5.3 kg/d; P=0.04) and digestibility (545 versus 523 g/kg; P=0.03) of AWS were higher for calves fed HF than for those fed LF diets. As a result, digestible DM intake of AWS was higher for HF than LF (3.1 versus 2.8 kg/d; P

Ponderosa pine trees occupy over 15 million hectares of rangeland in western North America. Pregnant cows often consume pine needles (PN), and subsequently abort. The protein-to-energy ratio may be important in the ability of cattle to tolerate dietary terpenes. Tannins often co-occur with terpenes and may also influence diet selection. The objective of this experiment was to determine if the protein-to-energy ratio or the addition of quebracho tannin to cattle diets would influence PN consumption. In trial 1, 15 cows in moderate body condition were assigned to high (15.4% CP), medium (10.2% CP), or low (4.9% CP) dietary protein treatments for 12 d. In trial 2, 15 cows were assigned to high (5%), medium (2.5%), or no (0%) quebracho tannin diets for 8 d. In both trials, green PN were offered at 0930 h for 90 min. There was a treatment effect (P = 0.05) and a treatment × day interaction (P = 0.01) for PN consumption, as cattle on the high CP treatment consumed more PN than cattle on the medium and low CP diets for 4 and 6 d, respectively. Initially, treatments did not differ (P > 0.09), but from d 3 to 9 cattle on the high CP treatment ate more PN than the other treatments. There was a day × treatment interaction (P = 0.002) for PN consumption; cattle on the 2.5% tannin treatment consumed less PN than did animals on the other treatments. Cattle are apparently unable to tolerate high quantities of PN terpenes on a low-protein diet. Tannins may influence PN consumption, but the mechanism is unknown.

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 0.05). 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.

Thirty-two crossbred lambs (BW = 31.2 ± 4.7 kg; 16 females, 16 males) housed in individual pens were used to investigate the relationship between nutrient supply and taste preferences in ruminants. Experiment 1 determined whether an imbalanced CP supply would alter preferences for feeds containing flavors designed to elicit either umami (U) or a mixture (1/3:1/3:1/3) of umami, sweet, and bitter (M) tastes. Lambs were randomly allocated to either a low (LP; 10.9% CP) or a high (HP; 20.4% CP) CP diet for 21 d. Afterward, lambs were presented during 21 d with a choice of the same LP or HP diet unflavored (LPC or HPC, respectively) or flavored (0.1% as fed) with U (LPU or HPU, respectively) or M (LPM or HPM). Experiment 2 determined the influence of CP status on preference for dietary CP, bitter taste, and sweet taste elicited by sucrose or a noncaloric sweetener. In test 1, sixteen lambs previously fed LP or HP for 42 d in Exp. 1 could choose between the HP and LP diets. In test 2, the remaining 16 lambs from Exp. 1 were offered a choice between unflavored LP or HP diets or the same diets flavored (0.066% as fed) with a bitter flavor. In test 3, the 16 lambs from test 1 were offered a choice between an unflavored diet (LP or HP) and the same diet flavored with sucrose (0.2%) or a noncaloric sweetener (0.066%). In Exp. 1, when offered a choice, all lambs showed a preference (P < 0.05) for the unflavored diet except for LP lambs, who clearly preferred (P < 0.05) LPU (72% of total DMI) over LPC. However, preference for LPU progressively decreased (P < 0.05) as time of exposure to the choice increased. In Exp. 2 (test 1), lambs previously fed LP progressively increased (P < 0.05) total DMI when presented with LP and HP, whereas consumption was constant for lambs previously fed HP and offered a choice of LP and HP diets. At the onset of test 2, lambs fed LP progressively reduced (P < 0.05) preference for the bitter flavor from 53 to 34%. In test 3, lambs previously fed LP diets consumed less (P < 0.05) sweetener- than sucrose-supplemented diet, whereas lambs previously offered HP diets consumed more sweetener- than sucrose-supplemented diet. In summary, protein-restricted lambs were able to differentiate and increase consumption of U-flavored feeds. However, this increase disappeared over time. These results indicate that lambs are able to sense dietary CP content and modulate short-term consumption of flavored feeds based on their nutrient requirements.

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 1h after food presentation, and sampled at 1, 2, and 3h 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 1h 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. Fil: Villalba, Juan J.. State University Of Utah; Estados Unidos Fil: Catanese, Francisco Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; Argentina Fil: Provenza, Frederick D.. State University Of Utah; Estados Unidos Fil: Distel, Roberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; Argentina

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 offivelambswerefirstofferedALFfor 30 minfollowed byeitherTForRCGfor3.5 h in a2 ×2 factorialarrangementofa 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 sampleswere collected and analyzed for dry matterintakeand apparent digestibility of dry matter, energy (in Kcal), nitrogen and neutral detergentfiber. 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 gd −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. c � 2011 Society of Chemical Industry

This study determined whether early experiences of sheep with the same feed, but presented in multiple or single flavors, would influence intake, the profile of hormones involved in feed intake regulation, and the subsequent acceptability of novel feeds. Thirty-five 2-mo-old lambs were randomly assigned to 5 treatments (7 lambs/treatment). Lambs in 1 treatment (the diversity treatment) were simultaneously fed an unflavored plain ration of alfalfa (control) and barley (75:25; as-fed basis) and the same ration mixed (0.2%) with 1 of 3 flavors: 1) sweet, 2) umami, or 3) bitter. The other 4 treatments (monotonous diets) received only 1 of the 4 rations. All animals were fed their respective rations from 0800 to 1600 h for 60 d. On d 55, intake was recorded every 30 min for 8 h. On d 58, blood samples from lambs were collected at 1 h prefeeding and at 30, 60, 210, 300, and 540 min postfeeding. Preference tests were conducted by simultaneously offering novel feeds: 1) high-energy feed, 2) high-protein feed, 3) beet pulp mixed with phytochemicals, or 4) low-quality feed. Lambs in the diversity treatment consumed more feed than did lambs in the other treatments (P < 0.001). Lambs in the diversity treatment consumed equivalent amounts of plain and umami feeds, with a greater amount (P < 0.001) of the umami feed being consumed than the bitter and sweet feeds. Lambs in the diversity treatment tended to grow faster than did lambs in the other treatments (P=0.06). On d 55, lambs in the diversity treatment showed decreased (P < 0.05) feed intake compared with lambs in the other treatments during the 2 peaks of food consumption (30 and 270 min from feeding) and showed a trend for the least plasma concentrations of ghrelin (P=0.06). In contrast, lambs in the diversity treatment consumed more feed than did lambs exposed to monotonous flavors at 60, 90, 120, and 180 min from feeding (P < 0.05). Lambs in the diversity treatment also showed the least concentrations of cholecystokinin and glucagon-like peptide 1 (P < 0.001). There were trends for the greatest concentrations of leptin (P=0.14) and IGF-1 (P=0.16) in the diversity treatment, and for the least concentration of leptin in the bitter treatment (P=0.14). Previous experience with flavored feeds affected the preference of lambs for high-energy and low-quality feeds, and for beet pulp mixed with phytochemicals (treatment × feed × day effect; P < 0.05). Thus, exposure to diverse flavors has the potential to increase feed intake and induce a more even consumption of feed across time by reducing peaks and nadirs of intake compared with exposure to monotonous rations. Flavor diversity may also influence the initial acceptability of and preference for novel feeds.

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).

Global warming, as a consequence of excessive CO 2 production mainly due to anthropogenic actions, is one of the main concerns of society due to the effects it can cause in the survival of humans, plants and animals. Several climatic consequences have already been reported, such as warming the oceans and changing biodiversity in various regions of the planet. One of the greenhouse gases responsible for global warming, which causes a lot of concern, is methane gas from digestion of food by ruminants. Besides that, emissions of greenhouse gases are represented also by waste management, rice cultivation, burning of residues from agriculture and soil management for agricultural production. Among ruminants, sheep and goats play an important economic role mainly in Oceania, Asia and Africa. More than 50% of small ruminants of the world are located in arid region, indicating their adaptability and future suitability to increasing temperatures. The purpose of this review is to report current knowledge about the methane emission produced by small ruminants, addressing the different interfaces of this theme, and considering possible mitigation strategies.

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.

Domestic ruminant selectivity induces floristic changes in pasturelands, risking sustainability and limiting the subsequent availability of susceptible plant species. Development of preferences for species of lower nutritional quality may help to overcome those problems. In this study, we tested the hypothesis that early experience of sheep with a low-quality food (LQF) in a nutritional enriched context increases preference for LQF in adulthood. We predicted a higher proportional consumption of LQF in experienced lambs (EL) than in inexperienced lambs (IL) in choice situations involving LQF and alternative foods. Additionally, we determined intake of LQF by EL and IL at different levels of high-quality food (HQF) availability. From 60 to 210 days of age, EL were fed in separated feed bunks mature oat hay (LQF) simultaneously with sunflower meal (SM) and corn grain (CG), whereas IL were fed alfalfa hay (HQF) simultaneously with SM and CG. After exposure, EL and IL were offered LQF in free choice situations involving alternative foods, and also at five levels of HQF availability (100%, 75%, 50%, 25% and 0% of ad libitum intake). Proportional consumption of LQF was lower or similar in EL than IL. Intake of LQF was also lower or similar in EL than IL at all levels of HQF availability, except when the LQF was the only food available. Our results did not support the hypothesis that early experience with a LQF in a nutritional enriched context increases preference for LQF in adulthood. On the contrary, experience with LQF diminished subsequent preference for LQF in adulthood. It is proposed that, in the conditions of our study, continuous comparison between the LQF and the high-quality supplements (CG and SM) during the early exposure period lead to devaluation of LQF by EL through a simultaneous negative contrast effect.

BACKGROUND: Mixtures of plant species provide biochemical diversity to pastures which may enhance productivity while decreasing reliance on herbicides and insecticides. All plants contain secondary metabolites (PSMs) that interact in plant communities in a variety of ways. For instance, tannins are a group of highly reactive chemical compounds with the potential to interact with other PSM such as alkaloids and saponins, neutralizing their negative effects. Our objective was to determine whether tannins modify the foraging behavior of sheep grazing on varieties of alfalfa, birdsfoot trefoil and tall fescue with high and low concentrations of saponins, tannins and alkaloids, respectively. RESULTS: Lambs that received intraruminal infusions of tannins increased their consumption of the high-saponin variety of alfalfa and the high-alkaloid variety of tall fescue relative to lambs not infused with tannins (controls). Lambs infused with tannins and then offered choices among the three high-PSM varieties of the forages also manifested higher consumption of the high-alkaloid variety of tall fescue than control lambs. In contrast, lambs infused with tannins reduced their consumption of the high-tannin variety of birdsfoot trefoil. Thus lambs modified their foraging behavior as a function of the presence/absence of tannins in their rumens. CONCLUSIONS: These results indicate that ruminants are able to discriminate the specific post-ingestive effects of forage varieties with high concentrations of PSM, and that PSM complementarities are likely to increase the efficiency of use of diverse forages with different biochemistries. Copyright © 2009 Society of Chemical Industry

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.

Interactions among nutrients and secondary compounds in plants can influence the kinds and amounts of different forages herbivores ingest, but little is known about how the sequence of plant ingestion may influence these interactions. The physiological pathways and rates of nutrient and secondary compound metabolism in the body influence food intake by herbivores. On this basis, we predicted the sequence in which foods that vary in nutrients and secondary compounds are ingested would influence food intake and preference. In a 2 × 2 factorial experiment, we evaluated the relationship between the sequence of presenting two foods, one with terpenes and the other with tannins, and the time when lambs ate a nutritious food (alfalfa–barley), either before or after eating foods with tannins and terpenes. When alfalfa–barley was fed prior to the terpenes, intake of the terpene-containing food was lower than when alfalfa–barley was fed after terpenes ( P P > 0.10). Lambs ate more total foods with terpenes + tannins when fed tannins → terpenes → alfalfa/barley than when fed alfalfa/barley → tannins → terpenes ( P terpenes > tannins ( P tannins > terpenes ( P terpenes ( P

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 CaCO(3) (P 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.

BACKGROUND: A mixture of plant species adds biochemical diversity to pastures that may enhance productivity while decreasing reliance on herbicides and insecticides. All plants contain secondary metabolites (PSMs) that interact in plant communities in a variety of ways. Our objective was to determine if PSM diversity enhanced food intake when sheep were allowed to select from foods that varied in concentrations of tannins, saponins, and alkaloids. We hypothesized that intake of foods containing alkaloids would increase when sheep were offered supplemental foods with tannins and saponins. The alkaloid gramine is proteinaceous in nature, tannins bind to proteins in the gut, which enhances excretion of proteins, so we hypothesized tannins would bind to gramine and enhance its excretion from the body. The alkaloid ergotamine is steroidal, saponins have a high affinity for binding to lipid and steroidal compounds in the gut and then being excreted, so we hypothesized saponins would bind to ergotamine and enhance its excretion from the body. RESULTS: We found that sheep fed either gramine or ergotamine in combination with tannin- or saponin-containing foods had higher intakes of food than sheep offered only foods with gramine or ergotamine. CONCLUSION: These findings are consistent with the hypothesis that animals can neutralize the negative effects of alkaloids by ingesting tannins and saponins. Our results show that PSMs can complement one another to increase a herbivore's intake of unpalatable plant species, with the potential to maintain healthy animals and bio-diverse landscapes. Copyright © 2008 Society of Chemical Industry

Ruminants foraging on landscapes choose among plants that differ in nutritive value and kinds and amounts of plant secondary compounds (PSCs). We hypothesized that food availability and the sequence of food ingestion influence intake of PSCs and nutritious foods by sheep because PSCs increase need for nutrients. We fed two nutritious foods – alfalfa and alfalfa–barley mixture (50:50) – and three isoenergetic (DE: 2.9 Mcal/kg) and isonitrogenous (CP: 126 g/kg) foods that contained oxalates, tannins, or terpenes. The experiment consisted of an 8-d conditioning period and four trials in which we tested our hypotheses. In the conditioning period, the three PSC-containing foods were offered ad libitum but the two nutritious foods were restricted to 300 g/d and the daily intake of each food was measured. In trial 1, all five foods were offered from 0800 to 1600 h. In trial 2, the two nutritious foods were offered from 0800 to 1200 h whereas the three PSC-containing foods were offered from 1200 to 1600 h. In trial 3, the three PSC-containing foods were offered from 0800 to 1200 h while the two nutritious foods were offered for the next 4 h. Finally, in trial 4 all five foods were offered again from 0800 to 1600 h. Each trial lasted 8 d, except the last one, which was 5 d. In the four trials, foods were offered ad libitum and the amount of each food ingested was measured daily at hourly intervals. As conditioning progressed, consumption of all three PSC-containing foods increased, and the pattern of eating changed from oxalate > tannin > terpene to tannins > oxalates > terpenes. During trial 1, lambs ate alfalfa–barley > alfalfa = tannins > oxalates = terpenes. In trial 2, sheep ate 1490 g/d of nutritious foods in the morning and 863 g/d of PSC-containing foods in the afternoon for a total of 2353 g/d. In trial 3, when the sequence was reversed, sheep ate 1021 g/d of PSC-containing foods in the morning and 1564 g/d of the nutritious foods in the afternoon for a total of 2585 g/d. By trial 4, the pattern of diet mixing had changed such that sheep ate alfalfa–barley > tannins > alfalfa = terpenes > oxalates. In summary, sheep ate more PSC, and more nutritious food, when PSCs were offered in the morning as opposed to the afternoon. Limiting the availability of nutritious alternatives encouraged animals to learn to use different kinds of PSCs and enhanced diet breadth. Beyond the effect of diet restriction, lambs learned the benefits of mixing food with tannins, terpenes, and oxalates and continued to do so even when they subsequently had ad libitum access to nutritious foods.