Roger E. Banner

Linking herbivore experience, varied diets, and plant biochemical diversity

Abstract We contend diets and habitats that allow animals to select among alternatives enable individuals to better meet needs for nutrients and to better cope with toxins. All plants contain toxins, and the amount of toxin an animal can ingest depends on the kinds and amounts of nutrients and toxins in the forages on offer. Nutrients and toxins both cause animals to satiate, and excesses of nutrients, nutrient imbalances, and toxins all limit food intake. Thus, individuals can better meet their needs for nutrients and regulate their intake of toxins when offered a variety of foods that differ in nutrients and toxins than when constrained to a single food, even if the food is “nutritionally balanced”. Food intake and preference also depend on differences in how individual animals are built morphologically and how they function physiologically, and marked variation is common even among closely related animals in needs for nutrients and abilities to cope with toxins. Transient food aversions compound the inefficiency of single-food diets—whether in confinement, on pastures, or on rangelands—by depressing intake among individual animals, even if they are suited “on average” to that nutrient or toxin profile. Thus, feeding and grazing practices that allow producers to capitalize on the individuality of animals are likely to improve performance of the herd by enabling the uniqueness of individuals to become manifest. Finally, past experiences play a crucial role in an animal’s propensity to learn to eat different foods. When herbivores are allowed to eat only the most preferred plants, they are not likely to learn to mix foods high in nutrients with foods that contain toxins. Conversely, herbivores encouraged to eat all plants in an area are more likely to learn to eat mixes of plants that mitigate toxicity. Experienced animals who have learned to eat a variety of foods that differ in nutrients and toxins do so even when nutritious alternatives are available, whereas naive animals familiar only with the nutritious alternatives eat only that subset of familiar foods. Different systems of management alter how animals forage. Continuous grazing at low stock densities encourages selectivity and reduces diet and habitat breadth, whereas short-duration grazing at high stock densities increases diet and habitat breadth. Thus, what was traditionally considered proper grazing management—rotational grazing at low stock densities—may have trained generations of livestock to “eat the best and leave the rest” thus inadvertently accelerating a decline in biodiversity and an increase in the abundance of less desirable plant species.

Differences in Home Range and Habitat Use among Individuals in a Cattle Herd

Abstract Numerous studies suggest some cows use certain areas (e.g. riparian habitats) more than others (e.g. uplands), but the research generally has been based on observations of small numbers of animals or on general inspections of entire herds. Consequently, it is not known if individual animals differ in home range (HR) and habitat use (HU) or if behavioral characteristics are a valid selection tool to decrease cattle use of riparian habitats. We conducted field observations of the differences in HR and HU among adult cows on summer range in Idaho. We located 116 cows on 4970 occasions during 1990, and 87 cows on 3995 occasions during 1991. Individual cows occupied one of four HR areas, and the majority (78%) showed high consistency in HR, despite drought, ad hoc management procedures and occasional herding. Thirty-three percent (n = 29) of the 87 animals monitored during 1990 and 1991 exhibited total HR fidelity between years, whereas 45% (n = 39), 18% (n = 16) and 3% (n = 3) of the animals differed slightly, moderately and substantially in HR use. All cows tended to shift their activities (i.e., centroid) to the south, apparently in response to decreasing water availability between 1990 and 1991. Cows in the four HR groups differed in the degree to which they foraged and rested in riparian and upland habitats, largely depending on the physical characteristics of the HR area. Given the high degree of home range fidelity in our study and those of others, we submit that selective culling may effectively change cattle distribution and decrease the use of riparian areas.

Supplemental barley and charcoal increase intake of sagebrush by lambs.

We evaluated the influence of supplemental barley and activated charcoal on the intake of sagebrush by lambs in individual pens. In 3 experiments, lambs were fed sagebrush (harvested and chopped to 2-3 cm) during the morning; they were fed a basal diet of alfalfa pellets in the afternoon. In the first experiment, lambs supplemented with activated charcoal + barley ate more A. tridentata ssp. vaseyana than lambs supplemented with barley (304 vs. 248 g; P = .071). A second set of experiments, which consisted of 3 trials, determined the effects of activated charcoal, barley, and subspecies of sagebrush on intake of sagebrush. Lambs supplemented with activated charcoal + barley ate more A. tridentata ssp. vaseyana (Trial 1; 292 vs. 225 g; P = .086), and more A. tridentata ssp. tridentata (Trial 2; 371 vs. 255 g; P = .031) than lambs supplemented with barley. In Trial 3, lambs supplemented with barley ate more sagebrush than lambs that were not supplemented (480 vs. 318 g; P = .0002). A third set of experiments compared activated charcoal + barley, barley, and no supplement in 2 trials. In Trial 1, lambs supplemented with activated charcoal + barley or barley generally ate more A. tridentata ssp. vaseyana than lambs not supplemented (P = .017). In Trial 2, lambs supplemented with activated charcoal + barley ate slightly more A. tridentata ssp. vaseyana than lambs supplemented with barley, and they ate substantially more than lambs not supplemented (P = .032). Collectively, the results suggest that energy from supplemental barley increased intake of sagebrush by lambs fed a basal ration of alfalfa pellets which are high in protein, and that activated charcoal played a minor role in further increasing intake of sagebrush. DOI:10.2458/azu_jrm_v53i4_banner

Dietary Habits and Social Interactions Affect Choice of Feeding Location by Sheep

Abstract Individuals often occur in subgroups that differ in their choice of forage and habitat, even within the same environment. Different foods occur in disparate locations and thus differences in dietary habits could provide one explanation for the formation of subgroups and their use of the environment. In addition, subgroups may form as a result of social interactions. We conducted experiments to study the effects of food preference and social interactions on choice of feeding location by lambs. In 1992, 12 lambs that had been reared together were separated into two groups of six lambs. Groups were conditioned to prefer one of two grains, either milo ( Sorghum bicolor ) or wheat ( Triticum aestivum ) by feeding milo or wheat for 14 days. Lambs were conditioned to avoid the other grain by following its ingestion with a mild dose of the toxin lithium chloride (LiCl) on 3 consecutive days. During testing, milo and wheat were placed at opposite ends of a 0.25 ha pasture. Lambs were first allowed to feed as groups consisting of three lambs that preferred milo and three lambs that preferred wheat, and then allowed to feed as groups in which one lamb preferred milo with three lambs that preferred wheat, and vice versa. Under both conditions, lambs always foraged on their preferred food, even when the locations of the foods were switched. In 1993, we repeated the study from 1992 in a larger pasture (1 ha) and without the use of LiCl. Lambs were reared in three different groups and fed either milo (Group 1), wheat (Group 2), or half of the lambs were fed milo and the other half were fed wheat (Group 3) for 4 months to condition a preference for either milo or wheat. When we combined lambs that preferred milo from Group 1 with lambs that preferred wheat from Group 2 to form subgroups of strangers, lambs fed in different locations. Conversely, social interactions and food preferences both affected choice of foraging location when lambs were reared together (companions). For instance, some lambs that preferred wheat grazed in the vicinity while peers ate milo, whereas lambs that preferred milo grazed in the vicinity while peers ate wheat. In other cases, one or two lambs separated from the rest of the group and ate their preferred grain. We conclude that food preference had a primary influence on choice of foraging location when lambs were reared separately (strangers) and preferred different foods. Food preferences and social interactions both influenced choice of foraging location for companions unless animals were made averse to one of the foods with LiCl, in which case dietary preferences overrode social influences.

Observations of Sheep Foraging in Familiar and Unfamiliar Environments: Familiarity with the Environment Influences Diet Selection

Abstract We determined if familiarity with a pasture decreased the importance of social interactions in food selection and choice of foraging location by lambs with different dietary preferences. Lambs in three treatments (18 lambs per treatment) were reared separately for 2 months and exposed daily to a 1-ha experimental pasture (Treatment 1), to a 0.5-ha pasture with similar forage species to those in the 1-ha experimental pasture (Treatment 2), or reared in confinement and not allowed to graze (Treatment 3). Half of the lambs in each treatment were fed milo ( Sorghum bicolor ) and half were fed wheat ( Triticum aestivum ) daily for 2 months to condition preferences for milo and wheat, respectively. During testing, subgroups of three lambs that were conditioned to prefer milo and three that were conditioned to prefer wheat (three subgroups per treatment) were exposed simultaneously to the 1-ha experimental pasture to determine if social influences affected food selection when milo and wheat were placed at opposite ends of the pasture (100 m apart). We found: (1) subgroups of lambs familiar with the pasture typically consumed different foods, depending on whether they preferred milo or wheat; (2) subgroups of lambs naive to the pasture typically foraged together on the same food; (3) preferences for either milo or wheat persisted for animals familiar with the experimental pasture, whereas lambs naive to the pasture acquired preferences for both foods. Thus, these results suggest social factors can override food preferences in a novel environment, but food preferences may be more influential in food selection in a familiar environment.

Sagebrush Ingestion by Lambs: Effects of Experience and Macronutrients

We investigated how experience early in life and macronutrient content of the diet influenced intake of mountain big sagebrush (Artemisia tridentata Nutt. ssp. v a s e y a n a (Rydb.) Beetle) by sheep. In the first part of our study, 2-month-old lambs were exposed as a group for 2 mo to a 70% barley-30% soybean meal ration (300 g/hd/day) that contained increasing amounts sagebrush (1 to 20%). Control lambs received grain without sagebrush. All lambs had access to alfalfa hay and pellets ad libitum. When lambs were tested at 6 months of age, prior exposure had no effect on sagebrush consumption after the first 4 days of the trial. When sagebrush comprised 20% of an alfalfa/barley ration, lambs ate the sagebrush ration readily even when a nutritious alternative was offered indicating the flavor of sagebrush did not prevent lambs from feeding. Increasing the amount of sagebrush in the ration from 50% to 75% resulted in lambs eating less of the barley/sagebrush ration, but daily intake of sagebrush remained constant throughout the 4 day trial, presumably because toxins (terpenes) limited intake of sagebrush. In the second part of our study, lambs experienced with sagebrush were fed 250 g/hd/day of barley, and nutritional status was varied by offering alfalfa pellets at 33% or 80% of ad libitum (1.2 and 2.7 times maintenance, respectively) to determine if dietary energy levels affected intake of sagebrush. Each day lambs received a 50/50 sagebrush/barley supplement ad libitum for 1 hour. Lambs fed at 33% of ad libitum consumed more of the sagebrush/barley supplement than lambs fed at 80% of ad libitum. Thus, additional energy did not enable lambs to consume more sagebrush. In the last trial, lambs in both treatments were fed a basal ration of alfalfa pellets at 50% of ad libitum. Each morning for 1 hour, lambs were offered macronutrient supplements containing either 50% barley/50% sagebrush (high energy) or 25% barley/25% soybean meal/50% sagebrush (high energy and protein). Lambs consumed the same amount of sagebrush regardless of supplement. Thus, supplemental protein did not improve sagebrush consumption. We conclude lambs readily ingested a high-energy ration containing sagebrush, regardless of exposure early in life, suggesting toxins, not flavor, control intake of sagebrush. Further, supplementing lambs with energy or protein failed to improve intake of sagebrush, which suggests these macronutrients did not enhance detoxification of sagebrush.

SPITTLEBUG AND BUFFELGRASS RESPONSES TO SUMMER FIRES IN MEXICO

Summer burning was used to reduce spittlebug (Aeneolamia albofasciata Lall.) populations in buffelgrass [Cenchrus ciliaris (L.) Link] on the Carbo Livestock Research Station in Sonora, Mexico. Five treatments included (1) an untreated control; (2) burning 7-14 days before the summer rains when the insect and the plant were inactive; (3) burning after the accumulation of 50 mm of summer precipitation during insect egg hatch or the second leaf stage; (4) burning between the second and third instars or early culm elongation; (5) and burning between the fifth instar and adult stages or active plant growth during the summer growing season. Summer burning after the accumulation of 50 mm of precipitation and between the egg hatch and the third instars or between the second leaf stage and early culm elongation reduced spittlebug nymph and adult populations by 100% and appeared to stimulate buffelgrass growth for 3 and 4 years post treatment. Burning at the peak of buffelgrass live biomass production effectively controlled spittlebug populations but reduced plant production by almost 50% for 4 years post-treatment. Equally detrimental was the untreated control where nymph and adult spittlebug populations killed more than 50% of the buffelgrass population. Summer fires conducted after 50 mm of precipitation were easier to control than fires conducted before the growing season when plant material was dry.

Soil Physicochemical Changes Following Buffelgrass Establishment in Mexico

Clearing brush from rangeland and seeding it to buffelgrass (Cenchrus ciliaris L.) is a popular range improvement practice in Mexico, but no data are available on the effects of these practices on soil properties. Twenty-nine study sites were randomly selected across 3 major climatic regions in Mexico: 13 in the northwest, 11 in the northeast, and 5 in the southeast. Soils under buffelgrass stands more than 10 years old and on adjacent virgin rangelands were sampled at 0-10, 10-20, and 20-30 cm depths to quantify sand, silt, clay, organic C, total N, pH, EC, CEC, available P, and exchangeable Ca2+, Mg2+, Na+, and K+.Because soil variables were not significantly (P 0.05) different among depths, only data from the surface horizon received further analysis. Soils in the northwest had higher (P 0.05) sand content and were particularly low in total N (0.08%), Ca2+, and K+, while soils of wetter and warmer southeast Mexico were significantly (P 0.05) higher than the other two regions in measures of soil fertili...

Effect of planting method and species on germination and survival of perennial wheatgrasses (agropyron spp.) seeded during drought in the moulouya plain of morocco

Abstract The effect of three methods of seeding four species of perennial wheat‐grasses ( Agropyron spp.) on three range sites in the Moulouya Plain of Morocco, North Africa, on germination and survivability during drought was evaluated. A conventional method of land preparation and seeding was compared to two different techniques using a rangeland drill in 1984. Agropyron elongatum (Host) Beauv., A. intermedium (Host) Beauv., A. trichophorum (Link) Richt., and A. cristatum (L.) Gaertn. were seeded on two shallow‐soil sites dominated by Stipa tenassicima L. and Artemisia herba‐alba Asso and a deep‐soil site dominated by A. herba‐alba in 1984. Plant density was measured in 1985 and 1988. On the shallow, more xeric sites, the conventional method of site preparation and seeding favored establishment. On these sites, species having large seed characteristics ( A. elongatum, A. intermedium and A. trichophorum) were more adept (P > 0.05) at establishment during droughty conditions than the smaller seeded A. cri...

Effects of chiseling and sulfur fertilization on infiltration, soil moisture, and vegetation parameters in the Ait Rbaa perimeter of central Morocco

Abstract This study evaluated the effectiveness of chiseling and elemental sulfur fertilization upon soil moisture and vegetation response on an upland and a swale site with fine loamy, carbonatic, thermic, typic calcixeroll soils in the Ait Rbaa Perimeter of Central Morocco. Ponding infiltration, soil water content on a mass basis of the 0‐to 10‐cm and 10‐ to 20‐cm soil layers, peak season biomass production, and botanical composition were monitored during the two growing seasons following the treatments (1984/85 and 1985/86). Chiseling significantly (p < .001) improved infiltration on both sites, although the improvement was greater on the finer and less stony swale site. The land treatment also increased the average water content of the top 20 cm of soil. In the chiseled treatments, average soil water content decreased with soil depth on the upland site, while it increased on the swale site. Both the average infiltration rates of 5 cm of water and the average water content generally varied inversely wi...