Intensive Sheep Grazing Research Articles

The effect of the addition of a companion forage to a perennial ryegrass sward on ewe and lamb performance

Ireland's competitive advantage in sheepmeat production is based on the efficient and cost effective production and utilisation of pasture. The objective of this study was to assess the influence of binary mixtures of perennial ryegrass (Lolium perenne L.) plus a companion forage on ewe and lamb performance at pasture. Five sward mixtures were compared, namely; i) perennial ryegrass (Lolium perenne L.;PRG), ii) PRG plus white clover (Trifolium repens L.;PRG + WC), iii) PRG plus red clover (Trifolium pratense L.;PRG + RC), iv) PRG plus plantain (Plantago lanceolate L.;PRG + Plan) and v) PRG plus chicory (Chicorium intybus L.;PRG + Chic). Five farmlets with one sward treatment assigned to each were established which 23 ewes plus their lambs grazed from March to December for the years 2018 to 2021 inclusive. Farmlets were rotationally grazed, stocked at 11.5 ewes/ha and received 130 kg nitrogen/ha/year. Lambs were weaned on average at 15 weeks of age. Post-weaning a leader-follower grazing system was implemented with lambs grazing ahead of the ewes. Post weaning, lambs were weighed fortnightly and drafted at a live weight of 42 kg in June and increasing by 1 kg per month thereafter to produce a target carcass weight of 20 kg. Results show that lamb lifetime average daily gain (ADG) was greater for lambs grazing all binary sward mixtures relative to grazing PRG. Relative to PRG, lamb lifetime ADG was increased by between 17 g/day (PRG + Plan; P < 0.01) to 31 g/day (PRG + RC, and PRG + Chic; P < 0.001) and subsequently the number of days required to reach slaughter (DTS) was reduced by between 15.8 days (PRG + Plan; P < 0.01) to 28.6 days (PRG + RC; P < 0.001) with the addition of a companion forage. As a result of lower DTS, the average total number of anthelmintic treatments administered per lamb was significantly reduced for lambs grazing on all of the binary sward mixtures relative to PRG (P < 0.001). Scanned litter size and ewe milk yield were similar across all sward types as were ewe body weight (BW) and body condition score (BCS) from mating up until 6 weeks post-lambing (P > 0.05). Of the ewes retained from one production year to the next, those grazing PRG + WC, PRG + RC and PRG + Plan had a greater BW than those grazing PRG at the second mating event (P < 0.05), whilst, PRG + RC, PRG + Plan and PRG + Chic ewes had a greater BCS than PRG ewes (P < 0.05). These results suggest the suitability of binary sward mixtures under an intensive sheep grazing system to improve ewe and lamb performance at pasture.

Integration of grazing and herbicide application improves management of barb goatgrass and medusahead in pasture and rangelands

The invasive annual grasses barb goatgrass (Aegilops triuncialis L.) and medusahead (Elymus caput-medusae L.) are widespread in western states and present management challenges on grasslands. To develop an integrated management strategy for these species, we treated sites in five pastures in Mendocino County, comparing combinations of intensive sheep grazing, glyphosate herbicide (low and high), and application timings (tillering, boot and heading stage). We found that grazing alone reduced barb goatgrass spikelet densities by 68% and the number of seeds per spikelet by 35%. Both rates of glyphosate application without grazing had similar effects on seed production. High and low glyphosate application at tillering resulted in almost complete control of both target species. Boot- and heading-stage applications reduced barb goatgrass density by 39% and 32%, respectively. Application at the boot stage also resulted in an 82% reduction in number of seeds per barb goatgrass spikelet. Our results suggest that intensive grazing may be a useful management strategy to reduce barb goatgrass and medusahead spikelet densities and barb goatgrass seed numbers, especially when integrated with a boot- or heading-stage glyphosate application.

The effect of increasing pasture species on herbage production, chemical composition and utilization under intensive sheep grazing

AbstractA complete randomized design was used to investigate the effect of increasing pasture species on herbage production, chemical composition and utilization under intensive sheep grazing. Four experimental farmlets were established, namely perennial ryegrass (Lolium perenne) only, receiving 163 kg N ha−1 year−1 (PRG); a perennial ryegrass and white clover (Trifolium repens) sward (PRGWC); a six species sward containing two grasses, two legumes and two herbs (6S); and a nine species sward containing three grasses, three legumes and three herbs (9S), each receiving 90 kg N ha−1 year−1. Ewes (12.5 ewes ha−1) and lambs rotationally grazed each farmlet from turnout post‐lambing until housing. Target pre‐grazing herbage mass (above 4 cm) was 1,200 kg dry‐matter (DM) ha−1, Target post‐grazing sward height was 4 cm for all rotations. Herbage samples were collected for DM yield, botanical and chemical composition determination at each grazing. Annual DM production of the 6S, 9S and PRG swards was similar (10.3, 9.9 and 9.9 ± 0.5 t DM ha−1, respectively) despite differences in N application. The 6S sward, however, had greater annual DM production compared to the PRGWC sward (9.1 t DM ha−1, p &lt; 0.05). Herb proportions decreased in the 6S and 9S swards from 2015 to 2016 (p &lt; 0.05) resulting in increased proportions of grass in these swards (p &lt; 0.05). In conclusion, the PRGWC, 6S and 9S swards produced similar annual herbage DM from lower N inputs to PRG swards; however, maintaining the proportions of herbs is a challenge under intensive sheep grazing.

The impact of intensive sheep grazing in the spring on the vegetation of xerothermic grasslands in Stawska Góra nature reserve

The aim of study was to assess the impact of intensive sheep grazing in the spring on the vegetation of xerothermic grasslands in Stawska Gora nature reserve, particularly the Carlina onopordifolia seedling development and preferences concerning the ingestion of specific plant species, including shrubs and tree-understory. In May 2015, 40 specimens of the Świniarka Sheep and Polish Lowland Sheep were grazed in an area of 1.85 ha. Phytosociological releves were taken using the Braun-Blanquet method. Changes in the plant cover were assessed in July 2015 under grazing and non-grazing conditions. The flowery grassland plants were assigned to the Cirsio-Brachypodion pinnati alliance and thicket communities - to the Rhamno-Prunetea class. There was confirmed that community under study is distinguished by a large share of Carlina onopordifolia . The number of Carlina onopordifolia seedlings in the grazed areas was significantly greater than in the non-grazed areas. The sheep ingested all herbaceous plants appearing in the grasslands in May, except for the poisonous Adonis vernalis and most of shrubs. Preliminary research results indicate that grazing in the spring led to a decreased cover-abundance of Brachypodium pinnatum and some shrubs, and also - to smaller share of dead organic matter in the plant cover. It can create favourable conditions for the generative reproduction of xerothermic plants such as Carlina onopordifolia .

Continuous moderate grazing management promotes biomass production in Patagonian arid rangelands

Domestic grazing effects on primary productivity and community structure are controversial in rangeland ecology and frequently misunderstood. Although directly related with secondary production, biomass stock and biomass production at species level (biomass composition) has been relegated in field studies, especially in arid rangelands co-dominated by woody species. We estimated grazing effects on aboveground biomass in a temperate mixed grass-shrub steppe of Patagonia. We compared exclusion of sheep with two levels of continuous grazing: moderate (light) and intensive sheep grazing in an average precipitation year. Total green biomass (productivity) was twice as high in moderately grazed paddocks as in those without grazing and intensively grazed pastures, while standing dead grass biomass stock only decreased in intensive grazing. Shrub biomass was not modified by grazing management. In addition, grazing modified grass specific biomass composition, thus diminishing biomass quality in intensively grazed areas. This work provides evidence that in arid rangelands, continuous moderate grazing management could be an effective tool to increase productivity compared to grazing exclusion. Furthermore, moderate grazing would not cause major undesired changes in species composition. However, a potential risk of land use intensification exists because intensive grazing could decrease biomass production as well as promote negative composition changes.

Impact of tree planting configuration and grazing restriction on canopy interception and soil hydrological properties: implications for flood mitigation in silvopastoral systems

Compaction of upper soil layers by intensive sheep grazing has been connected with increased local flood risk in silvopastoral systems. A 12�week field study was conducted at the Henfaes Research Station near Bangor, Wales to compare canopy interception, soil water infiltration, and bulk density between a control pasture and two silvopastoral tree planting configurations: trees clumped in fenced-off ungrazed plots and trees planted evenly and grazed. The study's aim was to characterize the potential of these tree planting configurations to reduce local flood risk. Automated throughfall gauges were installed in each silvopastoral treatment along with a similarly designed control gauge located in the grazed control pasture. Soil water infiltration and bulk density were measured 20 times in a stratified random design for each treatment and control. Results showed that the mean soil infiltration capacity in clumped configuration was 504% greater than the control pasture and 454% greater than the even spaced configuration. Average canopy interception was higher in the clumped configuration (34%) than in the even spaced configuration (28%). Soil bulk density was lower in the clumped configuration (0.87�Mg/m3) than in the control pasture (0.93�Mg/m3) and even spaced configuration (1�Mg/m3). Results suggest that silvopastoral systems are more likely to benefit from clumped and ungrazed tree configurations than from evenly-spaced and grazed tree configurations due to enhanced infiltration, lower soil compaction, and increased canopy interception. Our findings support the growing evidence base that fenced-off tree areas in silvopastoral settings can increase infiltration and thus reduce local flood risk. This article is protected by copyright. All rights reserved.

Farming for pests? Local and landscape-scale effects of grassland management on rabbit densities

In recent decades in the UK, there has been an increasing trend in numbers of the European wild rabbit, a significant agricultural pest typically associated with grassland habitats. However, the relationship between rabbit abundance and grassland management, in particular grazing, has not been sufficiently explained. We studied rabbit densities in seven pasture-dominated sites in north-east England between autumn and spring in two consecutive years, and used generalised linear mixed models and generalised additive models to explore relationships between habitat and management variables and rabbit abundance at local (field) and landscape scales. At the local scale high rabbit densities were significantly associated with small fields and the very short, homogeneous swards created by intensive sheep grazing during autumn and winter. At the landscape scale, high rabbit numbers were associated with sites with most field margins and a predator removal policy. Our results indicate that landscape management may play a central role in explaining rabbit abundance and distribution in grasslands. We suggest that current pasture management may create favourable conditions for high rabbit densities, and consequently boost numbers of this significant pest species.

Intensified grazing affects endemic plant and gastropod diversity in alpine grasslands of the Southern Carpathian mountains (Romania)

Alpine grasslands in the Southern Carpathian Mts, Romania, harbour an extraordinarily high diversity of plants and invertebrates, including Carpathic endemics. In the past decades, intensive sheep grazing has caused a dramatic decrease in biodiversity and even led to eroded soils at many places in the Carpathians. Because of limited food resources, sheep are increasingly forced to graze on steep slopes, which were formerly not grazed by livestock and are considered as local biodiversity hotspots. We examined species richness, abundance and number of endemic vascular plants and terrestrial gastropods on steep slopes that were either grazed by sheep or ungrazed by livestock in two areas of the Southern Carpathians. On calcareous soils in the Bucegi Mts, a total of 177 vascular plant and 19 gastropod species were recorded. Twelve plant species (6.8%) and three gastropod species (15.8%) were endemic to the Carpathians. Grazed sites had lower plant and gastropod species richness than ungrazed sites. Furthermore, grazed sites harboured fewer gastropod species endemic to the Carpathians than ungrazed sites. On acid soils in the Fagaras Mts, a total of 96 vascular plant and nine gastropod species were found. In this mountain area, however, grazed and ungrazed sites did not differ in species richness, abundance and number of endemic plant and gastropod species. Our findings confirm the high biodiversity of grasslands on steep slopes in the Southern Carpathian Mts and caution against increasing grazing pressure in these refuges for relic plants and gastropods as well as for other invertebrates.

Positive short-term effects of sheep grazing on the alpine avifauna

Grazing by large herbivores may negatively affect bird populations. This is of great conservation concern in areas with intensive sheep grazing. Sheep management varies substantially between regions, but no study has been performed in less intensively grazed systems. In a fully replicated, landscape scale experiment with three levels of sheep grazing, we tested whether the abundance and diversity of an assemblage of mountain birds were negatively affected by grazing or if grazing facilitated the bird assemblage. Density of birds was higher at high sheep density compared with low sheep density or no sheep by the fourth grazing season, while there was no clear effect on bird diversity. Thus, agricultural traditions and land use politics determining sheep density may change the density of avifauna in either positive or negative directions.

Overgrazing effects on vegetation cover and properties of volcanic ash soil in the páramo of Llangahua and La Esperanza (Tungurahua, Ecuador)

Abstract. The páramo is a high‐altitude ecosystem of the northern Andes. The vegetation is continuous, with grasses as the dominant groundcover. Because of their high water retention, páramos play a fundamental role in water availability for all the population of the inter‐Andean valleys. There are many studies of this specific ecosystem, but very few are focussed on overgrazing and its effect on vegetation and soil properties. Intensive grazing started less than 20 years ago and was studied in a representative area in the western Cordillera of central Ecuador covered by recent volcanic ash deposits. Intensive sheep grazing has led to a strong decline in the number of plant species, the replacement of the tussock grass vegetation by a short carpet grass vegetation, and an increase of bare land. In that area, the upper 50 cm of Andisols are deeply affected by a convergent decrease of Al and Fe oxalate and pyrophosphate in soil extracts, carbon contents decrease from 100 g kg–1 to less than 50 g kg–1 in the humid zone, from 70 to 40 g kg–1 in the dry zone and a reduction of water‐retention capacity at −33 kPa matrix potential from 800 g kg–1 to 200 g kg–1 in humid zones, from 350 to less than 100 g kg–1 in drier areas. They showed also a decrease in the macrostructure and the development of a highly water repellent microstructure. All these important transformations favour the development of aeolian erosion in dry areas, runoff on bare surfaces, and gully erosion on slopes. The role of the páramo in water‐regulation of this ecosystem seems to have been adversely affected for the future.

Holocene landscape development and human impact in the Connemara Uplands, Western Ireland

AimAim Investigate: (1) the role of human impact in shaping the landscape and particularly the initiation of blanket bog; (2) the short‐lived abrupt changes and their causation; (3) the phenomenon of large‐scale upland peat erosion to answer the question of when and why erosion of upland blanket peat commenced in the Connemara uplands.LocationLough Maumeen in the Maumeen Gap, Connemara, Western Ireland.MethodsPollen, sedimentary analysis and 14C dating on the lake sediment cores.ResultsPollen diagrams, charcoal fragments, bulk and dry densities, mineral content (or loss‐on‐ignition), whole core magnetic susceptibility, specific magnetic susceptibility for the core profile.Main conclusionsPine‐dominated woodland developed from 9250 BP. Human activities effected the deforestation between 5050–4000 BP. Peat bog initiated on the wet hollow ground in the gap during the elm decline. The major expansion of blanket bog landscape in the upland commenced at 4000 BP following immediately the Taxus decline. Human impact was the dynamic force responsible for the destruction of the woodland and the formation of blanket bog in the upland. Three episodes of short‐lived erosion events were identified between 8650–8400 BP, 5450–5250 BP, and 600–200 cal. BP, respectively. They are very different from each other in their causation. Large‐scale peat erosion is a recent phenomenon. It has been caused by intensive sheep grazing, which has been extended to the upland blanket bogs since the late eighteen century.

Paleolimnological assessment of human impacts in Lake Blanca, SE Uruguay

Paleolimnological techniques were used to assess human impacts onLake Blanca, a small (0.6 km2), coastal fresh waterbodyin southern Uruguay, which is the drinking water source for ∼100,000 localresidents. We retrieved a core that extends to about 1100 14Cyr BP. 210Pb ages, organic mater, CO3, totalcarbon, nutrients, fossil pigments and diatoms allowed us to establishlimnological conditions before and after cultural impacts. Soil removal(1880–1960) and intensive cattle and sheep grazing (1943–1966) ledto gully formation in the catchment. This watershed erosion resulted inincreased sedimentation rates. The aquatic system appeared to be mesotrophicwith dominance of epibenthic diatoms until ∼1966, at which timeeutrophication intensified with forestry activities. Increases in nutrients, aswell as blooms of planktonic diatoms, were observed. During the last decade,tourist/urban development as well as high drinking water demand caused areduction in lake area. Subsequent marked increases in rainfall led to furtherphytoplankton blooms and macrophyte proliferation.

Towards an environmental history of the Bowmont Valley and the northern Cheviot Hills

ABSTRACT The many and complex landscape changes that have occurred in the northern Cheviot Hills in the last c. 1000years are reviewed. The approach taken is to examine this period using, predominantly, palaeoenvironmental techniques, and the intention is to indicate the power of such reconstructions when allied to a secure and precise timescale. Palaeoenvironmental analyses identify important landscape changes not generally detected from documentary or archaeological data. The discussion here will address issues relating to medieval sheep-ranching, to the impacts on landscapes and society of the ‘Little Ice Age’, and the loss of biodiversity introduced by intensive sheep-grazing in the last c. 250 years.

Seasonal variation in the morphology of perennial ryegrass (Lolium perenne) and cocksfoot (Dactylis glomerata) plants and populations in pastures under intensive sheep grazing

SUMMARYThe morphology of independent plants of ‘Grasslands Ruanui’ perennial ryegrass (Lolium perenneL.) and three cultivars of cocksfoot (Dactylis glomerataL.) (‘Grasslands Apanui’, ‘Grasslands Kara’ and ‘Grasslands Wana’) in mixed pastures under intensive sheep grazing was studied at Palmerston North, New Zealand during 1991/92.Both perennial ryegrass and cocksfoot exhibited a similar pattern of clonal growth and population structure. Distribution of plants among various orders of branching showed a relatively stable pattern through most of the year except in spring, when stem decay and plant fragmentation exceeded apical growth and regeneration, causing an increase in the proportion of small plants and a corresponding decrease of larger plants. This pattern was similar to that previously reported for white clover (Trifolium repensL.). Nevertheless, seasonal variation in plant structure (number of leaves, tillers and stems per plant) was small, but variation in organ size (DW or length) was greater. Stolon formation through elongation of internodes occurred throughout the year, but was associated primarily with flowering.Grazing management caused no differences in plant structure between species or among the cocksfoot cultivars, but did affect the size of organs, and hence plants. Cocksfoot plants were 50–60% heavier than perennial ryegrass under rotational grazing. Under set stocking, only perennial ryegrass and Wana cocksfoot exhibited sufficient phenotypic plasticity to survive, both Kara and Apanui cocksfoot failed to persist. The only consistent difference between the species was greater flowering in perennial ryegrass than in cocksfoot, in both the proportion of plants flowering, and the number of flowering tillers per plant. Both species produced stolons throughout the year, although perennial ryegrass and Wana cocksfoot had a higher proportion of plants with stolons than Apanui and Kara cocksfoot. Length and DW of stolons per plant were similar in both species.As there was little variation in plant structure and plant density, length of stolons per unit area tended to parallel seasonal changes in pasture tiller density. The role of grazing management in the survival of tillers and plants, and subsequent performance of grass species in pastures is discussed.

The effect of blending white clover varieties and their contribution to a mixed grass/clover sward under continuous sheep stocking

AbstractThe effect of blending small‐ and medium‐leaved white clovers together in a mixture of varieties was examined under continuous sheep stocking over a period of three years. Four varieties were used, S184 and Gwenda, small‐leaved varieties suitable for intensive sheep grazing, together with medium leaved varieties Menna and Donna, which are mainly used in general purpose seed mixtures for medium term leys. The small‐leaved varieties were blended with Menna or Donna, sown with a commercial grass mixture and managed as near as possible to farm practice. Although the leaf size of Gwenda is only slightly greater than that of S184, blends based on these two small‐leaved varieties behaved differently. In spring of the first harvest year the yield of Gwenda and of the clover in mixtures containing Gwenda was 27% greater than the yield of the same mixtures which contained S184. As the season progressed this difference decreased. In terms of total annual yields and saving in fertilizer N, the benefits of including white clover in a seed mixture were more pronounced when Menna was mixed with S184 and Gwenda, rather than when Donna was used, although both varieties are in the medium‐leaf category. It was concluded that the slower establishment and the lower clover yield of S184, when compared with larger leaved varieties, can be overcome by blending with a variety that is slightly larger in leaf size, such as Menna, although the choice of variety may depend on sward management and its persistency under grazing.

Morphology of perennial ryegrass (Lolium perenne) plants in pastures under intensive sheep grazing

SUMMARYThe morphology of independent plants of perennial ryegrass (Lolium perenneL.) in mixed swards under intensive sheep grazing was studied at Palmerston North, New Zealand in 1988/89. Intact plants of two cultivars, ‘Grasslands Nui’ and ‘Grasslands Ariki’, were sampled from pastures under rotational grazing, set stocking, and a combination of both systems, every 2 months for 16 months, by taking turves (250 × 250 mm) and washing out the plants. Characters measured for each plant were: number of flower heads, leaves and tillers; basal stem and internode stolon length; flower head, leaf blade, leaf sheath and stolon dry weight (DW). Additional pasture data on tiller density and dispersion and herbage DW to ground level were also collected.Perennial rye grass exhibited a strong clonal growth pattern similar to that of white clover (Trifolium repensL.) but with a better balance between growth at the apex and death of old basal stem. Release of branch stolons to form new plants was regular, which maintained population stability. Formation of internode (I) stolon appeared to be a response of heavily shaded tillers for survival by elevation of the growing point to a more favourable position. The total DW of ryegrass stolon in pastures was greater than that of the companion white clover.There was little seasonal variation in number of tillers or basal (B) stem length per plant. During the reproductive period (late spring/early summer) plants were heavier and had more leaves and internode stolon than at other times of the year. Grazing management had little effect on plant structure, but plants under rotational grazing had 75% greater DW, less basal stem and reduced probability of internode stolon formation than plants under set stocking. Nui plants had heavier but fewer tillers than Ariki did, resulting in little difference in plant DW. Ariki had fewer single-tiller plants and a higher proportion of multiple-tiller (&gt; 7) plants than Nui had. The structure of the populations was not affected by season, management or cultivar and remained stable throughout the year, with a log-normal distribution of plant size. Because of the uniformity of plant structure, plant density in pastures paralleled tiller density, averaging 1900, 3360 and 2330 plants/m2for rotationally grazed, set stocked and combined grazing treatments respectively.In view of the strong influence that grazing management can have on ryegrass performance and persistence in pastures, the lack of response at the level of plant and population structure to grazing management suggests that some other level of organization within the ecology of the pasture is of greater importance.

Establishment and growth of Senecio jacobaea L. and Senecio erucifolius L. in grassland

Summary Senecio erucifolius L. (hoary ragwort) has become conspicuous on roadside verges in southern England. Like Senecio jacobaea L. it is poisonous, so it might be a threat to animal production. In boxed swards the growth of S. jacobaea was less adversely affected by the greater competition from grass with a high level of nitrogen fertilizer than was the growth of S. erucifolius. Also, young S. jacobaea plants showed a much greater ability to regrow after their shoots had been cut at ground level. In a range of grassland managements S. jacobaea established better from seed than did S. erucifolius. Establishment of both species on molehills was poor because of the likelihood that the seedlings would be disturbed or even buried by fresh mole activity. Ten months after sowing, seedlings of S. jacobaea had persisted well in the higher nitrogen environment of ex‐cow‐dung patches, whereas S. erucifolius had not. Under intensive sheep grazing, in the absence of fertilizer, transplants of S. erucifolius had much greater root dry weights than did those of S. jacobaea. Also, in regrowth after cattle grazing on a fertilized sward, S. jacobaea plants had greater shoot dry weights than did S. erucifolius. Thus, although S. erucifolius can establish from seed in bare patches in an intensively grazed sward it is likely to be less persistent than S. jacobaea if the gaps are ex‐dung patches or if nitrogen fertilizer is applied.

TALL FESCUE FOR FINISHING LAMBS AND FLUSHING EWES IN HAWKES BAY

Because of the many problems experienced in Hawkes Bay with traditional ryegrass pastures - drought, grass grub, stem weevil, ryegrass staggers - a research programme to evaluate tall fescue was initiated. Four short term trials have compared the nutritive value for sheep of two tall fescue cultivars (Roa and Demeter) with Nui ryegrass, all sown with white clover. All pasture types had similar quality for finishing lambs, although regrowth after a silage cut was better than previously grazed pastures, especia!!y for Nui. In the droughts of 1982 and 1983, tall fescue pastures were superior to those of Nui in both quantity and quality of feed for ewes prior to mating. This advantage resulted in an average of 18 more lambs being born per 100 ewes mated. Provided it persists, continues to produce well, and does not cause serious animal health problems under intensive sheep grazing, these results show that tall fescue should have an important role to play in Hawkes Bay and similar environments. Keywords: tall fescue, perennial ryegrass, lamb production, ewe production.

BREEDING A WHITE CLOVER ADAPTED TO SOUTHERN LOWLAND REGIONS OF NEW ZEALAND

White clover populations from Europe and New Zealand together with ecotypes collected from old pastures in Southland-Otago were evaluated as spaced plants at Gore. Plants were screened for herbage production and morphological and flowering characteristics. The Southland ecotypes and North Island hill country material are adapted to active growth in spring and summer. Their dense growth habit ensures continued production of branched stolons from nodal meristems which is necessary for high clover yield and persistence under intensive sheep grazing. In this region flowering characteristics are unimportant in relation to agronomic performance. Some largerleaved Huia and French lines have high-yielding features which are evident during autumn under lenient grazing. Hybrids between superior plants showing adaptive and high yie!ding features are being screened in order to select new types with the desired characteristics. Keywords: White clover, Trifolium repens L., plant breeding, southern region, ecotypes, growth, morphology.

Pronghorn Reactions to Winter Sheep Grazing, Plant Communities, and Topography in the Great Basin

The winter distribution of pronghorn over a 142-km2 area on the Desert Experimental Range was significantly related to sheep grazing during the current winter, presence of black sagebrush, and topographic characteristics. Even moderate sheep use during the dormant period left grazing units relatively unfavorable for pronghorn until spring regrowth-at least on ranges where key pronghorn forage plants were in short supply. Winter use areas preferred by pronghorn were above the valley bottoms in rolling to broken topography where black sagebrush communities were evident. Movement characteristics of pronghorn have allowed many of them to readily locate rested grazing units, and, therefore, avoid severe dietary competition with sheep. The Great Basin and other parts of the Intermountain West contain about 16 million ha of low-shrub cold desert. Most of these lands are publicly owned, and their primary use has traditionally been the grazing of sheep in winter and cattle in various seasons. In the last decade or so land managers have intensified efforts to consider the needs of wild animals, and require specific information to consistently make good management decisions. Information is available on pronghorn diets, water requirements, and predator losses (Beale and Holmgren 1975, Beale and Smith 1970, Beale and Smith 1973), but no intensive study has been accomplished in the Great Basin region to document the effects of livestock grazing systems on pronghorn (Antilocapra americana) populations Kindschy et al. 1978). Neither have the impact of other uses of the low-shrub desert on pronghorn been well documented for the Great Basin. A study to probe the effects of winter sheep grazing and certain environmental factors on pronghorn distribution wasconducted on the USDA Forest Service Desert Experimental Range near Milford, Utah, during the winters of 1976-81. Pronghorns thrive best on ranges with a diversity of grass-forbshrub communities (Autenrieth 1978), but are widely adaptable to different forage conditions across the total range of the species. The severity of competition between pronghorns and domestic livestock appears to vary greatly with differences in species of livestock, season of the year, and plant species available to the foraging ruminants (Salwasser 1980, Yoakum 1980). Although pronghorn habitat has mainly been manipulated by livestock grazing, many proposed energy, mineral, and defense activities threaten severe habitat disruptions. Winter ranges are often especially critical for pronghorn and are of particular concern (Kindschy et al. 1978). When the most important plants in the pronghorn's diet are a minor component of the vegetation, widespread surface disturbances or intensive sheep grazing of all available habitat could result in increased winter mortality for the pronghorn. The size and stability of pronghorn winter home ranges appear to be important in the animal's ability to adapt to newly created unfavorable habitat situations. Bayless (1969) found the pronghorn's winter home range to average 10-1 1 kM2, but one-half of the Authors are principal range scientist, Intermountain Forest and Range Experiment Station, Shrub Sciences Laboratory, Provo, Utah 84601; and wildlife biologist, Utah Division of Wildlife Resources, Cedar City, Utah 84720. Authors thank range technician John Kinney for his initiative and consistency of observation which made this study possible. Manuscript received Jan. 21, 1983. animals observed shifted home range at least once during the winter. This suggests that pronghorns may be flexible in their selection and use of wintering areas, although Howard et al. (1980) reported pronghorn avoided rough, broken terrain.