Forage choice in pasturelands: Influence on cattle ...

Forage choice in pasturelands: Influence on cattle foraging behavior and performance1,2 J. J. Villalba,* R. Cabassu,* and S. A. Gunter‡3 * Department of Wildland Resources, Utah State University, Logan 84322; ‡USDA, Agricultural Research Service, Southern Plains Range Research Station, 2000 18th Street, Woodward, OK 73801

ABSTRACT: 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 < 0.01). Animals in CHOICE grazed SAN > 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.

Key Words: activity, grazing, legumes, mixed diets, tall fescue © 2015 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2015.93 doi:10.2527/jas2014-8667 INTRODUCTION Cattle evolved grazing in diverse plant communities, consuming arrays of feeds of different chemical and physical characteristics (Provenza et al., 2007). A diverse diet provides an appropriate balance of nutrients to herbivores, allowing for greater growth and reproduction than grazing a single forage species (Westoby 1978). Synergies among forages may lead to a more efficient use of the resource with improved value to agriculture, reducing environmental impacts caused by livestock (Totty et al., 2013; Beukes et al., 2014), enhancing animal health (Crozier et al., 2006), and improving the quality (Maughan et al., 2014) and safety (Wells et al., 2005) of animal products.

1This research was supported by grants from the Utah Agricultural

Experiment Station, the Utah Irrigated Pasture Grants Program, and the Pleiades Foundation. Financial support for R. Cabassu from ISARA-Lyon, France and for A. Boubaker from the Fulbright Scholar Program is acknowledged. This paper is published with the approval of the Director, Utah Agricultural Experiment Station, and Utah State University as journal paper number 8737. 2We acknowledge R. Stott for veterinary services; D. Adams, G. Johnson, S. Hunt, A. Boubaker, C. Spackman, and D. Forester for technical support. 3Corresponding author: [email protected] Received October 28, 2014. Accepted January 26, 2015.

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Complementarities among different forage species have been observed with combinations of ryegrass and clover (Venning et al., 2004) or a herb sward mix (Hutton et al., 2011) because these diverse diets increase animal production relative to monocultures of ryegrass. Forage diversity also implies different levels of spatial aggregation of forage species, ranging from uniform mixes to separated swards. Spatial segregation of plant species in patches (strips of different widths and lengths) may reduce searching time and handling costs as well as overcome many difficulties inherent in establishing and maintaining mixed pastures (Chapman et al., 2007). Much of the research to date on the effects of forage diversity on animal behavior and performance has been conducted by contrasting monocultures with combinations of 2 forage species. Little is known about how higher order complementarities, like combinations of legumes and a grasses presented in patches, affect foraging behavior and performance of cattle. Thus, we determined if combinations of adjacent pastures of 3 forage species (alfalfa, sainfoin, and tall fescue) led to complementary relationships that affected cattle foraging behavior, performance, blood urea N (BUN), and fecal parameters relative to cattle foraging monocultures of the same forage species. MATERIALS AND METHODS We determined the foraging behavior and ADG of beef calves offered a choice of a grass (tall fescue) and 2 legumes (sainfoin, alfalfa) or monocultures of each species. The experiment was conducted at the Utah State University pasture research facility in Lewiston (41° 56ʹ N, 111° 52ʹ W) according to procedures approved by the Utah State University Institutional Animal Care and Use Committee (approval # 2228). Pasture Design Four pasture treatments were established on irrigated land at the research facility in spring of 2009. The soil was tilled, fertilized (50 Kg N/ha), and irrigated to prepare an adequate seedbed. After the soil had dried sufficiently to be crossed with a tractor, seeds were drilled and rolled. Tall fescue (TF), alfalfa (ALF), and sainfoin (SAN) were seeded at a rate of 22, 22, and 50 Kg of pure live seed/ha, respectively. Legume seeds were inoculated with the appropriate Rhizobium inoculant before planting. Plant establishment was enhanced and then maintained by sprinkler irrigation at 1-wk intervals (at approximately 50 mm/wk throughout the growing season). Treatments involved monocultures of: 1) TF (Schedonorus arundinaceus var. Kentucky 32), 2) ALF

(Medicago sativa var. Vernal), 3) SAN (Onobrychis viciifolia var. Shoshone), and 4) a choice of strips of TF, ALF, and SAN (CHOICE). There were 3 spatial replications (blocks) for each treatment of 97 × 66 m or 0.64 ha each. Blocks in the CHOICE treatment were formed by three 0.21-ha strips of approximately 32-m wide × 66-m long seeded with TF, ALF, and SAN, respectively. Thus, in each CHOICE block, cattle could freely graze on any of the 3 species on offer. The perimeters of the experimental blocks were fenced using t-posts and electric fence. Grazing Experiment Pastures were grazed from June 14 through August 23, 2013 with 3 fall-born Angus calves/(treatment × block; n = 3 × 3 = 9 animals/treatment). The calves averaged 333 kg ± 6 kg initial BW and 370 ± 5 kg final BW. Pastures were strip-grazed using temporary electric fences which were moved daily to allow access to the TF, legumes (ALF, SAN), and CHOICE. A temporary electric fence was set behind the animal to prevent grazing of regrowth. Herbage DM per unit of area in treatment-replicate was assessed on June 26, July 2, and August 7, 14, and 20 by taking 3 random samples (cut to the ground using hand clippers) per treatment-replicate from a 0.1089-m2 frame. Herbage samples were also used to determine the chemical composition of the forages in each pasture. Samples were dried at 60°C and then ground using a Wiley Mill (Thomas Scientific, Swedesboro, NJ) with a 1-mm screen. Throughout the experiment, animals had free access to water and trace-mineral salt blocks. Swards were in vegetative/late vegetative stage of growth at a height of 25 to 50 cm and all plots provided calves with ad libitum herbage. The area of daily strips of pastures was set to provide at least ~140% of the total forage, determined on a whole-treatment-replicate basis that calves consumed on the previous day. Depending on herbage mass, each day calves were given a new grazing area that ranged between 100 m2 and 200 m2 (50,000 to 100,000 Kg BW/ha), and on any day, all treatments were offered the same grazing area. There were 2 experimental periods, Period 1: June 14 to July 15, and Period 2: August 5 to August 23. Between periods, animals grazed an overflow sward of endophyte-free tall fescue (var. Kentucky 32) until experimental forages were ready to be grazed again. At the end of Period 1, refused tall fescue (the least preferred forage) in the CHOICE treatments was cut with a swather such that biomass values were similar (~2 to 2.5 tons/ha) for all treatments containing tall fescue (TF and CHOICE) during Period 2. Calves were weighed (unshrunk weights) at the beginning and end of each grazing period to estimate ADG. Animals were weighed at 0800 h before grazing.

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Grass-legume choices and cattle behavior

Scan Sampling

Chemical Analyses

On June 25 and 27 and for 3 mornings each week thereafter, we recorded foraging behavior of calves immediately after they had been given access to fresh strips of pasture. Three observers (each assigned to 4 blocks) recorded grazing patterns for each calf in a block. Calves were differentially marked using 3 different colored ear tags within a block. The foraging behavior of calves was recorded by each observer from a 3-m-high observation tower adjacent to each spatial replication. We used scan sampling (Altmann, 1974) at 5-min intervals from 0730 to 0930 h to assess the incidence of feeding on each of the forage species and bouts of inactivity. Frequency of feeding on each species was calculated as a percentage of the total number of scans in which animals were feeding. The total number of scans of grazing bouts and nongrazing bouts (bouts of inactivity such as not eating, resting, and searching) were also recorded. Groups of calves normally grazed together (>95% of the time) on the same plant species. If individuals were performing different behaviors, each behavior was recorded for each individual.

Herbage and fecal samples were analyzed for DM (AOAC, 1990), CP (AOAC 1990), NDF (Van Soest et al., 1991), ADF, ash, and minerals (AOAC, 2002). Blood urea nitrogen analyses were performed at the Logan Regional Hospital on a Vitro 950 Clinical Analyzer (Ortho Clinical Diagnostics, Rochester, NY).

Behavioral Levels of Activity Two randomly selected calves per block and for all treatments were fitted with a pedometer (Icetag, IceRobotics, Roslin, UK) on their left front leg for the duration of Period 2 (August 5 to 23). Activity levels and posture were measured with the use of these pedometers, which took second-to-second readings throughout the period, measuring the number of steps taken and the posture of the animal. Blood and Fecal Sampling Blood samples were drawn from all calves by puncture of the jugular vein at the end of each grazing period (July 15 and August 23) to determine BUN concentration as an indicator of the protein status of the animal (Hoffman et al., 2007). Samples were collected in vials (10 mL) without anticoagulant additives (BD Vacutainer, Franklin Lakes, NJ) before fences were moved for a new daily allowance of forage. Blood samples were centrifuged at 3,000 × g for 20 min to harvest serum and subsequently stored at -30°C until analyses. Fecal samples were taken from the rectum of each calf at the end of each grazing period before access to daily pasture allocation (July 15 and August 23). Samples were stored at -30°C and then freeze dried (PerkinElmer Instruments, Norwalk, CT) before chemical analyses.

Statistical Analyses Behavioral data were analyzed as a repeated measure design for treatments: ALF, TF, SA, and CHOICE (fixed effects) nested within 3 spatial replications (random effect). The response variables for behavioral data were percentage of scans recorded on each species relative to the total number of grazing bouts and data acquired from the pedometers (number of steps taken, lying bouts, percentage of time spent lying and standing). Data were downloaded with the provided IceRobotics software (version 2012) in a format of 1 summary record per day. An additional analysis was performed for the CHOICE treatment to determine the proportion of grazing events recorded for any single species during the 3-way choice relative to the total number of grazing events (i.e., preference). Data were analyzed as a split-plot design with day as the repeated measure in the analysis and forage (TF, ALF, SAN) as the within-replication factor in the analysis. The ADG, BUN, and DM, CP, NDF, ADF, ash, and mineral content of feces were analyzed as splitplot design with spatial replications nested within treatments (ALF, TF, SA, and CHOICE) and period as the repeated measure. Foraging behavior, animal performance, BUN, and chemical composition of feces were analyzed using a mixed-effects model (SAS Inst. Inc., Cary, NC, Version 9.1). The variance–covariance structure was selected based on the lowest Bayesian information criterion. The model diagnostics included testing for a normal distribution of the error residuals and homogeneity of variance. Means were analyzed using pairwise differences of least squares means. RESULTS Chemical Composition of the Forages Concentrations of NDF and ADF in all forages increased from June 26 to July 2 and then they decreased toward August 14 when they reached their lowest values (Table 1). Concentration of NDF was greater for TF than for the legumes. In contrast, concentration of CP was greater for the legumes than for TF, with the greatest values observed for ALF (August 14 and 20).

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Table 1. Means and SE of DM biomass availability and chemical content of the forages used in the experiment1

Parameter Pregrazing biomass, tonnes/ha Postgrazing biomass, tonnes/ha CP, % NDF, % ADF, % Ash, % Ca, % P, % Mg, % K, % Na, % Fe, ppm Mn, ppm Zn, ppm Cu (ppm) Pregrazing biomass, tonnes/ha Postgrazing biomass, tonnes/ha CP, % NDF, % ADF, % Ash, % Ca, % P, % Mg, % K, % Na, % Fe, ppm Mn, ppm Zn, ppm Cu, ppm Pregrazing biomass, tonnes/ha Postgrazing biomass, tonnes/ha CP, % NDF, % ADF, % Ash, % Ca, % P, % Mg, % K, % Na, % Fe, ppm Mn, ppm Zn, ppm Cu, ppm 1Fall

26 June 6.4 ± 0.6 ALF CHOICE 2.9 ± 0.3 3.2 ± 0.4 15.2 ± 0.4 45.1 ± 0.8 35.0 ± 1.5

2 July 6.5 ± 0.6 ALF CHOICE 3.0 ± 0.2 2.9 ± 0.3 14.1 ± 0.8 50.4 ± 1.3 38.4 ± 0.8 8.5 ± 0.3 1.4 ± 0.1 0.2 ± 0.01 0.5 ± 0.01 2.1 ± 0.01 0.1 ± 0.01 91.3 ± 6.7 40.0 ± 0.6 15.7 ± 0.9 6.7 ± 0.3

11.0 ± 1.3 SAN CHOICE 5.9 ± 0.5 3.9 ± 1.2 13.5 ± 1.0 46.4 ± 1.1 39.4 ± 1.4

10.9 ± 1.0 SAN CHOICE 9.6 ± 0.5 6.0 ± 2.1 13.8 ± 1.5 49.6 ± 1.4 40.1 ± 1.9 6.8 ± 0.2 1.0 ± 0.1 0.2 ± 0.01 0.4 ± 0.01 1.9 ± 0.2 0.1 ± 0.01 90 ± 6.1 42.0 ± 6.7 18.7 ± 1.3 5.0 ± 0.6

7.7 ± 0.5 TF CHOICE 2.3 ± 0.4 4.8 ± 1.3 6.8 ± 0.5 61.3 ± 0.9 37.8 ± 0.4

6.1 ± 0.6 TF CHOICE 2.4 ± 0.7 6.1 ± 0.5 6.7 ± 0.8 66.0 ± 0.6 40.1 ± 1.3 9.7 ± 0.3 0.3 ± 0.01 0.2 ± 0.01 0.2 ± 0.01 2.3 ± 0.01 0.1 ± 0.01 76.3 ± 10.7 43.0 ± 1.2 14 ± 1.5 3.0 ± 0.01

Pasture Alfalfa 7 August 4.3 ± 0.2 ALF CHOICE 1.8 ± 0.3 1.9 ± 0.3 18.3 ± 0.7 41.1 ± 0.1 34.0 ± 1.0

14 August 3.0 ± 0.2 ALF CHOICE 1.6 ± 0.1 1.3 ± 0.3 21.6 ± 0.8 37.0 ± 1.2 30.2 ± 0.2

20 August 4.2 ± 0.5 ALF CHOICE 1.2 ± 0.2 1.7 ± 0.7 19.6 ± 0.6 43.6 ± 0.4 35.5 ± 0.9 9.1 ± 0.2 1.2 ± 0.1 0.2 ± 0.01 0.6 ± 0.01 2.4 ± 0.2 0.1 ± 0.01 101.0 ± 7.6 45.7 ± 2.6 22.3 ± 0.9 8.3 ± 0.3

Sainfoin 4.6 ± 0.9 SAN CHOICE 2.3 ± 0.8 1.4 ± 0.4 15.9 ± 0.7 41.9 ± 2.6 37.4 ± 2.1

3.2 ± 0.8 SAN CHOICE 1.7 ± 0.9 1.3 ± 0.2 17.9 ± 1.8 38.0 ± 2.0 30.3 ± 1.3

6.0 ± 1.1 SAN CHOICE 2.4 ± 0.4 1.6 ± 0.5 17.0 ± 1.3 40.2 ± 0.1 35.0 ± 2.2 6.9 ± 0.1 1.0 ± 0.1 0.2 ± 0.01 0.4 ± 0.01 1.9 ± 0.2 0.0 ± 0.01 79.0 ± 5.0 41.0 ± 2.0 22.5 ± 2.5 6.5 ± 0.5

Tall Fescue 2.5 ± 0.5 TF CHOICE 1.1 ± 0.1 2.8 ± 0.6 12.5 ± 2.7 58.2 ± 2.0 36.8 ± 2.4

1.5 ± 0.3 TF CHOICE 0.5 ± 0.1 2.1 ± 0.1 14.3 ± 0.5 54.4 ± 1.3 34.3 ± 1.4

1.5 ± 0.3 TF CHOICE 0.5 ± 0.3 2.3 ± 0.1 12.0 ± 0.8 60.4 ± 1.3 38.8 ± 1.0 13.8 ± 0.4 0.5 ± 0.01 0.3 ± 0.01 0.4 ± 0.01 1.9 ± 0.1 0.1 ± 0.01 212.3 ± 36.8 64.7 ± 2.3 18.3 ± 1.7 4.3 ± 0.7

calves grazed monocultures of: (1) tall fescue (TF), (2) alfalfa (ALF), (3) sainfoin (SAN), or (4) a choice of TF, ALF, and SAN (CHOICE).


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Figure 1. Total grazing bouts (as a percent of total scans) for cattle allowed to strip-graze every day monocultures of: (1) tall fescue (TF), (2) alfalfa (ALF), (3) sainfoin (SAN), or (4) a choice of strips of TF, ALF, and SAN (CHOICE) during 2 grazing periods. Values are means for 3 spatial replications; SE are represented by vertical bars.

Concentrations of CP increased from the beginning of the experiment to August 14 and then stabilized until the last sampling date (Table 1). Ash content, Fe (August 20), and Mn (August 20) was greater, whereas Ca, Mg, Cu, and Fe (July 2) concentrations were lower for TF than for the legumes. Herbage Availability Dry matter content was greater for SAN than for ALF during Period 1 (June 26, July 2) and toward the end of Period 2 (August 20). Herbage availability was similar between legumes during the beginning and middle of Period 2 (August 7 and 14; Table 1). Tall fescue DM availability was comparable to ALF DM availability for Period 1 (June 26 and July 2), but it reached its lowest values toward the end of Period 2 (August 14 and 20; Table 1). The postgrazing herbage mass ranged between 25 and 50% of the pregrazing herbage mass (except for the SAN [July 2], which represented 88% of the pregrazing herbage mass; Table 1). After June 26, postgrazing herbage mass for TF in the CHOICE treatment did not reveal any level of utilization.

Scan Sampling Total Grazing Bouts. During Period 1 and averaged across treatments, the proportion of grazing events recorded during scan sampling was greater for calves in ALF (79%) and SAN (81%) than in TF (65%) and CHOICE (69%; SEM = 2.5%; P = 0.005), and no treatment by day interaction was detected (P = 0.27; Fig. 1). For Period 2, the incidence of grazing events recorded was SAN (91%) > TF (82%) > ALF (75%) = CHOICE (70%; SEM = 2.6%; P = 0.002), and no treatment × day interaction was detected (P = 0.70; Fig. 1). Preference. During Period 1, animals in CHOICE spent most of the daily 2-h sessions grazing SAN (57% of the grazing scans recorded) and they were observed more times grazing ALF (28% of the grazing scans recorded) than TF (15% of the grazing scans recorded; SEM = 3.4%; P = 0.0004; forage × day interaction; P = 0.52; Fig. 2). As for Period 1, animals in CHOICE spent most of the daily 2-h sessions grazing SAN (56% of the grazing scans recorded), whereas 42% of the grazing scans were recorded on ALF and only 2% on TF (SEM = 1.8%; P < 0.0001; forage × day interaction; P = 0.14; Fig. 2).

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Figure 2. Daily grazing bouts for cattle that strip-grazed every day a choice of spatially separated patches of tall fescue, alfalfa, and sainfoin during 2 grazing periods. Preferences for the different forages were assessed using scan sampling (represented as a percent of total grazing scans). Values are means for 3 spatial replications; SE are represented by vertical bars.

Behavioral Levels of Activity Overall activity as measured by the number of steps taken on a daily basis showed a significant treatment effect (P = 0.01). Calves on TF and CHOICE took a greater number of steps than calves grazing monocultures of legumes (ALF, SAN; Table 2). There was a tendency for a treatment by day interaction (P = 0.07), which was caused by a significant increase in activity by calves in CHOICE during August 20 and a subsequent decline (Fig. 3). There was no effect of treatment on the

total time spent standing or lying (P > 0.05; Table 2), which by definition are a linear combination (i.e., standing time = 24 – lying time) but there was an interaction between treatment and day (P = 0.01; Fig. 3). This interaction was mainly due to greater time spent standing for calves in CHOICE and TF compared to calves grazing monocultures of legumes, particularly ALF during August 8, 12, 15, 17, and 20 (Fig. 3). There was no effect of treatment or treatment by day interaction on the number of lying bouts (P > 0.05; Table 2).

Table 2. Average daily gain, blood urea nitrogen (BUN) and behavioral levels of activity in beef calves strip grazing alfalfa (ALF), tall fescue (TF), sainfoin (SAN), or a choice of all 3 forages (CHOICE)

Parameter ADG, kg/d BUN, mg/dL Steps, number/d Standing Time, h Lying Time, h Lying bouts a–cWithin

ALF 0.8a 18.4a

Period 1: June 14 to July 15 Treatment TF SAN CHOICE 0.4b 0.5b 1.0a 7.9b 17.0a 13.8c

a row, means without a common superscript differ (P < 0.05).

ALF 0.3a 19.0a 2012a 11.3 12.7 189

Period 2: August 6 to August 23 Treatment TF SAN CHOICE 0.3a 0.7b 0.4a 10.4b 15.7c 18.4a 2831b 1701a 2763b 11.8 11.7 12.1 12.2 12.3 11.9 334 432 390

SEM 0.1 1.0 215 0.3 0.3 136

P-value 0.003 0.005 0.01 0.46 0.46 0.63


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Figure 3. Number of steps taken and standing time on a daily basis for cattle allowed to strip-graze every day monocultures of: (1) tall fescue (TF), (2) alfalfa (ALF), (3) sainfoin (SAN), or (4) a choice of strips of TF, ALF, and SAN (CHOICE) during 2 grazing periods. Values are means for 3 spatial replications; SE are represented by vertical bars.

BUN and Fecal Chemistry Analyses of blood samples obtained at the end of each grazing period revealed a lower (P = 0.005) BUN concentration in calves from TF than for calves in the rest of the treatments (Table 2). In addition, BUN concentrations for Period 1 were greater for calves grazing monocultures of legumes (ALF and SAN) than for calves in CHOICE (P < 0.05), whereas BUN concentrations for Period 2 were greater for animals in ALF and CHOICE than for animals grazing a monoculture of SAN (Table 2), which caused a treatment by period interaction (P = 0.005; Table 2). Fecal DM increased in all treatments from Period 1 to Period 2 (P = 0.002), except for calves grazing a monoculture of SAN. Calves grazing a monoculture of TF showed the greatest values of fecal DM (Table 3). Calves in TF had the lowest concentrations of fecal CP, whereas animals in SAN had the greatest values (Table 3). In addition, fecal CP concentrations were similar between calves in ALF and CHOICE during Period 1 but concentrations of CP were greater for CHOICE than for ALF during Period 2, which caused a treatment by period interaction (P = 0.0004; Table 3). Fecal NDF concentration was the greatest for TF and the lowest for SAN (Periods 1 and 2) and CHOICE

(Period 2; treatment effect; P < 0.001; treatment by period interaction; P = 0.0003; Table 3). Fecal ADF concentration was greater for TF and SAN than for CHOICE and ALF (treatment effect; P = 0.02; treatment by period interaction; P = 0.09; Table 3). Calcium and Mg concentration were the lowest in feces from calves grazing a monoculture of TF (treatment effect; P < 0.001), with the greatest Ca and Mg concentration for SAN during Period 1 and greatest concentration of Mg for ALF during Period 2 (treatment by period interaction; P < 0.05; Table 3). Phosphorous concentration in feces was the greatest for calves in SAN and the lowest for CHOICE just during Period 1 (treatment effect; P = 0.14; treatment by period interaction; P = 0.0007; Table 3). Manganese concentration was the greatest in the feces of calves in SAN and CHOICE during Periods 1 and 2, respectively (treatment effect; P = 0.004; treatment by period interaction; P = 0.005; Table 3). Zinc concentration was the greatest in calves in SAN and the lowest for calves in TF (treatment effect; P < 0.001; treatment by period interaction; P = 0.11; Table 3). No differences were detected in the rest of the parameters assessed in feces (treatment effect; treatment by period interaction; P > 0.05).

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Table 3. Dry matter, CP, NDF, ADF, ash, and mineral concentration in feces from beef calves grazing different forages used in the experiment1 Date July 15 Parameter DM, % CP, % NDF, % ADF, % Ash, % Ca, % P, % Mg, % K, % Na, % Fe, ppm Mn, ppm Zn, ppm Cu, ppm

ALF 11.2a 16.6a 51.0a 39.2a 16.2ab 3.2a 0.5a 1.4a 1.4 0.58 709 202a 85ab 23

TF 11.4a 10.3b 59.6b 43.6b 22.8c 1.2b 0.5a 0.7b 1.4 0.45 733 161a 36c 37

SAN 15.7b 19.8c 46.7c 43.4b 18.4ab 4.0c 0.6b 1.7c 1.0 0.19 899 289b 117d 37

CHOICE 11.1a 14.1a 52.7a 41.0a 18.1ab 2.8a 0.4c 1.1d 1.6 0.46 640 180a 61ab 18

ALF 15.0b 16.3a 50.8a 40.5a 14.0ab 3.1a 0.6b 1.7c 0.9 0.21 642 171a 99ab 32

August 23 TF SAN 14.1b 12.9b 10.2b 20.8c 60.8b 44.4c 44.2b 43.5b 27.3d 14.8ab 1.3b 2.8a 0.6b 0.6b 0.9e 1.4a 1.5 1.1 0.31 0.18 764 778 172a 198a 43c 101d 44 29

CHOICE 13.0b 20.0c 41.5c 36.4a 18.6ae 3.1a 0.7b 1.4a 1.3 0.23 845 238c 93ae 27

SEM 0.96 0.79 1.88 1.69 1.01 0.22 0.04 0.08 0.17 0.11 84.7 20.5 10.0 13.2

P-value 0.002 0.0004 0.0003 0.02 0.001 0.003 0.0007 0.0003 0.11 0.36 0.12 0.005 0.04 0.09

a–eWithin 1Fall

a row, means without a common superscript differ (P < 0.05). calves grazed monocultures of tall fescue (TF), alfalfa (ALF), sainfoin (SAN), or a choice of TF, ALF, and SAN (CHOICE).

Average Daily Gains Calves grazing CHOICE and ALF had greater ADG (1.0 and 0.8 kg/d, respectively) than cattle grazing TF and SAN (0.4 and 0.5 kg/d, respectively) during Period 1, whereas calves in SAN (0.7 kg/d) had greater ADG than calves in ALF, TF (0.3 kg/d), and CHOICE (0.4 kg/d) during Period 2 (treatment effect; P = 0.06; treatment by period interaction; P = 0.003; Table 2). Averaged across periods, calves in SAN (0.6 kg/d), ALF (0.5 kg/d), and CHOICE (0.6 kg/d) had greater ADG than calves in TF (0.3 kg/d; P = 0.004). DISCUSSION Foraging Behavior: Choice Grass-Legumes Cattle grazing the CHOICE treatment in this experiment selected a diverse diet. At the beginning of each grazing session, cattle had ad libitum access to grass and legumes. Under these conditions, they could have eaten mainly the higher-quality legumes, but based on our scan data and consistent with a previous study (Maughan et al., 2014), they incorporated a significant proportion of tall fescue during Period 1 (15%), even though both legumes were of greater feeding value than tall fescue. A diverse diet enables ruminants to meet needs for nutrition and health (Westoby, 1978; Provenza and Villalba, 2006; Villalba et al., 2014) and/or minimize ingestion of toxins (Freeland and Janzen 1974). For instance, sheep and cattle ingest more endophyte-infected tall fescue and perform better when supplemented with

legumes such as alfalfa and birdsfoot trefoil (Lyman et al., 2012; Owens et al., 2012). Sheep and cattle offered a choice of grass and clover pastures consistently consume a mixed diet, with a partial preference for clover of about 70%. Animals select a diet of about 30% grass despite the fact that they could freely choose a diet of 100% clover—a forage of greater feeding value than grass—and meet their daily energy and protein requirements (reviewed by Chapman et al., 2007). This foraging pattern is consistent with the satiety hypothesis, which attributes changes in preference to transient food aversions due to flavors, nutrients, and toxins ingested too frequently or at high concentrations (Provenza, 1996). Gustatory, olfactory, and visual neurons stop responding to the taste of a particular food eaten to satiety, yet they continue to respond to other foods (Critchley and Rolls, 1996). This process, known as sensory-specific satiety (Rolls et al., 1982), reduces food intake and preference, whereas diverse oro-sensorial stimuli may restore the motivation to eat (Epstein et al., 2009). Reduced food acceptance also becomes pronounced when foods contain high levels of nutrients or nutrient imbalances. For instance, some suggest the inclusion of grass in the diet of ruminants is because grass allows animals to overcome constraints due to eating pure legume, which is forage normally high in protein (Cosgrove et al., 2001; Champion et al., 2004). A rapid release of ammonia from the soluble protein fraction of the legume in the rumen and subsequent uptake in the blood can condition food aversions (reviewed in Provenza, 1996). By mixing grass with a


legume, animals dilute protein ingestion and balance the ratio of energy to soluble protein, which reduces the rate of accumulation of ammonia in rumen fluid (Hill et al., 2009). It is likely that animals in ALF (high BUN concentrations for Periods 1 and 2) experienced the negative postingestive effects of excess nitrogen in their diet to a greater extent than cattle in the other treatments. Concentration of CP was lower for tall fescue than for legumes and consistent with such pattern, cattle in TF showed the lowest values of BUN and fecal CP for both periods. Sainfoin is a condensed tannin–containing legume and condensed tannins reduce rumen degradation of protein (McMahon et al., 1999) and increase the fraction of nonammonia nitrogen reaching the small intestine relative to other legumes without tannins (Waghorn et al., 1987). Thus, tannins in SAN and a reduced degradation of protein in the rumen may explain the lower BUN and greater fecal CP concentrations observed for animals grazing SAN. Concentration of condensed tannins in SAN was assessed for plants in SAN and CHOICE blocks during 2010 and 2012 and they ranged between 3% (August/ September) and 8% (May/June; Maughan et al., 2014). In contrast to Period 1 and based on scan data as well as post-grazing biomass recordings, the inclusion of tall fescue in the calves’ diet from the CHOICE treatment declined to very low levels during Period 2 (scans: 2%; postgrazing biomass: negligible). This response was in contrast to greater concentrations of CP and lower concentrations of fiber in TF during Period 2 than during Period 1. Thus, CP or fiber were not likely the limiting factors influencing calves’ preference for tall fescue in CHOICE. It is more likely that the reduced biomass of TF during Period 2 relative to Period 1 drove the aforementioned pattern of selection. High temperatures during the grazing periods (maximum, minimum, and average temperatures were 31, 12, and 22°C and 33, 14, and 24°C for Periods 1 and 2, respectively; Utah State University Climate Center) likely depressed the growth rate of this cool-season grass, leading to the low levels of biomass recorded during Period 2. Cattle in CHOICE clearly preferred SAN to ALF and this pattern was consistent for both periods. This response may be a consequence of a reduced preference for ALF due to subclinical bloat as animals learn to avoid foods that cause rumen distension (Villalba et al., 2009). Alfalfa is a bloating legume whereas SAN is not (Cooper et al., 1966). Alternatively, animals may have learned to prefer SAN over ALF due to the positive postingestive effects of SAN. Greater biomass availability for SAN during Period 1 and toward the end of Period 2 may have enhanced preferences for this legume. Alternatively, condensed tannins in SAN reduce methane emissions (Guglielmelli et al., 2011),

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thus increasing the efficiency of nutrient use in ruminants (Broderick, 1995). In addition, the greater fraction of nonammonia nitrogen reaching the small intestine in ruminants fed SAN relative to animals fed other legumes improves the ratio of essential amino acids to energy (Waghorn et al., 1987). Associations between such benefits and the sensory properties of SAN may have conditioned a preference for the legume in this experiment (Provenza and Villalba, 2006). Finally, because a rapid release of ammonia from the soluble protein fraction of the legume to the rumen causes reductions in food intake and preference (reviewed in Provenza, 1996), a potential reduction of rumen ammonia concentration in animals fed SAN relative to animals fed other forages may also explain the pattern of preference observed for this legume. Foraging Behavior: Choice Grass-Legume vs. Monocultures Based on scan samples, the lowest incidence of foraging bouts occurred for cattle in CHOICE during both periods. Nevertheless, it is worth noting that the foraging estimates described in this experiment may have been influenced by the time of the day that observations were taken. Cattle display differences in their feeding behavior throughout the day (e.g., Gibb et al., 2008). Scan samples were taken during a period of active grazing (i.e., immediately after animals had access to fresh pasture), but such observations were conducted for only 2 h/d. Patchiness and heterogeneity of herbage in the CHOICE treatment vs. uniformity in monocultures likely influenced foraging bouts during the scan sampling period. It has been predicted that if herbivores were to graze with a patch preference, then total intake would be reduced relative to the situation where animals eat equally from all patches (i.e., without rejecting any patch) and that this reduction would occur even at low stocking rates (Parsons and Dumont, 2003). The process of manifesting selectivity, like searching and switching among forage rows as it occurred in this experiment, reduces eating rate in ruminants (Chapman et al., 2007), an inefficiency that could not have occurred in treatments exposed to monocultures because alternatives were not available. The incidence of grazing was greater for calves in SAN during both test periods. This effect may be explained by the biochemical composition of SAN (e.g., a nonbloating tannin-containing legume leading to a reduced degradation of protein in the rumen; McMahon et al., 1999), which likely induced a greater motivation to eat relative to other forages. Reward from food consumption modulates the rate of forage intake and enhances the motivation to eat (Villalba and Provenza, 2000). The possibility that animals were

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more motivated to eat sainfoin than the rest of the forages is supported by the fact that calves in CHOICE preferred SAN to ALF or TF. The decrease in biomass and increase in nutritional quality of tall fescue from Period 1 to Period 2 may explain the increased number of recorded scans for calves in the TF treatment during Period 2 (82% of the scans) relative to Period 1 (65% of the scans). Behavioral levels of activity Calves on TF and CHOICE took a greater number of steps than calves grazing monocultures of legumes (ALF, SAN). As for the incidence of foraging bouts, it is likely that patchiness and heterogeneity of herbage in the CHOICE treatment drove this pattern. Cattle do not develop preferences for patches in homogeneous habitats, whereas they clearly develop patch preferences in heterogeneous areas (Bailey, 1995). It is suggested that this type of selectivity was what increased the number of steps taken by cattle in CHOICE relative to cattle grazing uniform monocultures of legumes. With more alternatives available, cattle may have walked more to select the different forages on offer than cattle grazing legume monocultures. Cattle in CHOICE took similar numbers of steps to cattle in TF but it is likely the reasons underlying this behavior were not the same. Because of the chemical composition of tall fescue, calves in TF grazed on the lowest nutritive value sward and showed the lowest values of ADG, BUN fecal CP, Ca, Mg, and Zn and the greatest fecal concentration of fiber. When physiological needs are not fully met, herbivores are more exploratory and eat more novel foods than when physiological conditions are adequate (Provenza et al., 1998; Egea et al., 2014). Thus, it is likely that exploratory behavior and the motivation to eat a forage other than TF explains the greater number of steps taken by calves in TF. In beef heifers, rumen fill affects short-term intake rate and grazing dynamics (Gregorini et al., 2007), whereas motivation to walk in dairy cows increases linearly with the level of food deprivation (Schütz et al., 2006; Gregorini et al., 2011). Food-deprived ewes walk longer distances for a food reward than unrestricted controls (Verbeek et al., 2011). In addition, challenging animals by presenting them with problems they cannot solve (i.e., finding alternative foods when grazing a monoculture of TF) is a source of frustration and stress which can negatively impact their welfare. In contrast, animals faced with problems that can be solved, such as acquiring an appropriate diet from the environment (i.e., a choice of legumes and TF), may lead to an enhancement in their welfare (Meehan and Mench, 2007).

Sward Characteristics, Behavior, and Performance Because food preference in herbivores is not random, time is lost while animals search for and handle preferred food items in a diverse plant community, which in turn reduces harvest efficiency (Chapman et al., 2007). Experiments offering animals the choice of alternative forage species such as ryegrass and white clover growing side-by-side, rather than sown as a conventional intermingled mixture, have provided evidence that animal performance benefits from having such a choice (Nuthall et al., 2000; Cosgrove et al., 2001). When grass and clover are planted in strips, as opposed to homogeneous mixtures, milk production by dairy cows increase by 11% (2.4 kg/cow/d; Cosgrove et al., 2001). Separation of plant species like in the present experiment minimizes the time needed to select and handle desired amounts of different forages. In addition, planting forages in strips overcomes many difficulties inherent in establishing and maintaining mixed pastures and also mimics what happens naturally as different plant species aggregate in response to environmental conditions (Chapman et al., 2007). In addition to the spatial aggregation of different forages, nutritional complementarities among diverse arrays of plant species have the potential to enhance animal production (Tilman, 1982). No forage has the perfect balance of nutrients found in a variety of forages (Westoby, 1978). Thus, by consuming a mixed diet, a forager obtains a more beneficial (and balanced) mixture of nutrients, allowing for greater growth and reproduction than grazing a monoculture (Westoby 1978; Provenza et al., 2007). Even when it appears logical that a diverse plant community increases animal productivity, information on the topic is scarce (Soder et al., 2007) and not fully consistent with this notion. For instance, it has been reported that species richness in pastures has minimal effects on cattle performance (Tracy and Faulkner, 2006). Sheep selecting a proportion of clover:grass of 70:30 show BW gains comparable to those animals grazing pure clover (Venning et al., 2004). In contrast, animals grazing just grass experience a decrease in productivity of about 25% relative to animals grazing a grass:clover mix (Venning et al., 2004). Consistent with these findings, ADG averaged across periods did not differ between animals in CHOICE and animals grazing monocultures of legumes but they were greater than ADG of animals grazing a monoculture of TF. Additionally, based on scan data, the lowest incidence of foraging bouts occurred for cattle in the CHOICE treatment. If this effect continued throughout the day, then it is possible that cattle in this treatment had greater efficiencies of feed conversion than animals grazing monocultures. In support of this, livestock offered a choice of food ingredients


sometimes show an improved feed efficiency compared to feeding a TMR (Zobel et al., 2006; Askar et al., 2006; Gorgulu et al., 2003). On the other hand, cattle in CHOICE walked more than animals grazing monocultures of legumes and this extra energy expenditure may have affected ADG. However, it has been shown that walking at constant speed is a low energy-cost process which requires ~9 kcal/100 kg BW to travel 1 km on level ground (DiMarco and Aello, 1998). Conclusions Cattle offered combinations of herbages preferred sainfoin > alfalfa > tall fescue and had ADG similar to cattle offered single legumes and greater than cattle offered just tall fescue. Thus, cattle given a diverse array of herbages can build a diet that leads to levels of productivity comparable to animals grazing legume monocultures—the herbages of greatest nutritional value—with the added benefit of maintaining plant species diversity in pasturelands. The lower number of grazing bouts and greater levels of activity recorded for cattle offered choices warrant further research to understand whether such behaviors are linked to improvements in foraging efficiency and/or animal welfare. LITERATURE CITED Altmann, J. 1974. Observational study of behavior: Sampling methods. Behavior 49:227–265. AOAC. 1990. In: Hilrich, K., editor, Method 989.03. Official methods of analysis. Assoc. Off. Anal. Chem., Washington, DC. p. 74–76. AOAC. 2002. Official methods of analysis. 17th ed. Assoc. Off. Anal. Chem., Arlington, VA. Askar, A. R., J. A. Guada, J. M. Gonzalez, A. de Vega, and C. Castrillo. 2006. Diet selection by growing lambs offered whole barley and a protein supplement, free choice: Effect on performance and digestion. Livest. Sci. 101:81–93. Bailey, D. W. 1995. Daily selection of feeding areas by cattle in homogeneous and heterogeneous environments. Appl. Anim. Behav. Sci. 45:183–200. Beukes, P. C., P. Gregorini, A. J. Romera, S. L. Woodward, E. N. Khaembah, D. F. Chapman, F. Nobilly, R. H. Bryant, G. R. Edwards, and D. A. Clark. 2014. The potential of diverse pastures to reduce nitrogen leaching on New Zealand dairy farms. Anim. Prod. Sci. 54:1971–1979. Broderick, G. A. 1995. Desirable characteristics of forage legumes for improving protein utilization in ruminants. J. Anim. Sci. 73:2760–2773. Champion, R. A., R. J. Orr, P. D. Penning, and S. M. Rutter. 2004. The effect of spatial scale of heterogeneity of two herbage species on the grazing behaviour of lactating sheep. Appl. Anim. Behav. Sci. 88:61–76. Chapman, D. F., A. J. Parsons, G. P. Cosgrove, D. J. Barker, D. M. Marotti, K. J. Venning, S. M. Rutter, J. Hill, and A. N. Thompson. 2007. Impacts of spatial patterns in pasture on animal grazing behavior, intake, and performance. Crop Sci. 47:399–415. Cooper, C. S., R. F. Eslick, and P. W. McDonald. 1966. Foam formation from extracts of 27 legume species in vitro. Crop Sci. 6:215–216.

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