Semi-arid Range Research Articles

10.4314/sajas.v40i5.65339

Undernutrition of cows grazing semi-arid range as a result of drought or heavy stocking rates reduces prenatal and pre-weaning growth of their ca lves. A mechanistic model has been developed that simulates the productivity of vegetation and cattle on semi-arid savanna rangeland in southern Africa. When cows are stocked at 0.200 cows/ha instead of 0.123 cows/ha the model predicted that empty body weights of their progeny at birth and weaning would be reduced by 2.9 and 43.8 kg, respectively. If all young ani mals are stocked at 0.22 animals/ha after weaning, diffe rences in empty body weight at weaning are predicte d to persist almost unchanged for a further two years. T he model also predicted that undernutrition of catt le aged 21 months would be followed by partial compensatory growth. Comparison of simulated results with data from experiments in Zimbabwe indicates that the model realistically simulates the effects of stocking rate on cattle growth.

Chemical composition and in vitro ruminal fermentation of common tree forages in the semi-arid range lands of India

The objective of study was to look for the promising tree leaves for feeding livestock particularly the small ruminants. Ten tree leaves were collected from semiarid region of Rajasthan and evaluated for their nutritional quality in terms of chemical composition as well as in vitro dry matter and organic matter digestibility (IVDMD and IVOMD). Most of the tree leaves were rich in CP content. OM, CP and ADF content of these collected tree leaves varied from 87.1 to 92.5%, 9.4 to 19.8% and 22.7 to 47.9% on DM basis, respectively. Rumen protozoal number decreased due to inclusion of Sapindus mukorossi, Azadirachta indica and Prosopis cineraria tree leaves in the incubation media. IVDMD, IVOMD, TVFA and propionate production significantly higher for Ailanthus excelsa tree leaves followed by Acacia arabica and Acacia senegal tree leaves. All the tested tree leaves had no effect on β-glucosidase and amylase enzyme activity. However, specific activity of carboxymethyl cellulase and xylanase reduced significantly due to addition of Sapindus mukorossi, Azadirachta indica and Prosopis cineraria tree leaves in the incubation medium. The results indicated that among the tree leaves tested in the present study Ailanthus excelsa, Acacia arabica and Acacia senegal are good tree fodder for feeding to the ruminants.

Creep-feeding to stimulate metabolic imprinting in nursing beef heifers: impacts on heifer growth, reproductive and physiological variables

This experiment compared growth, physiological, and reproductive responses of beef heifers with (MI) or without (CON) access to a creep-feeder, as a manner to stimulate metabolic imprinting while nursing their dams. On day 0, 60 Angus×Hereford heifers were ranked by BW and age (140±3 kg and 68±3 days), and assigned to pairs so all ranking criteria were similar between heifers within each pair. On day 1, pairs were randomly assigned to MI (n=15) or CON (n=15). From day 1 to 51, MI pairs and their dams were allocated to 15 drylot pens where heifers had ad libitum access to a corn-based supplement through a creep-feeder. The CON pairs and their dams were maintained in an adjacent single drylot pen. From day 52 to 111, treatments were managed as a single group on a semiarid range pasture. On day 111, heifers were weaned and allocated to two pastures (one pasture/treatment), receiving hay and a corn-based concentrate until day 326. Heifer BW was recorded before and at the end of the creep-feeding period (day 1 to 51), and on days 112 and 326. On days 0, 51, 111, 187, 261, and 325, jugular blood was collected and real-time ultrasonography for longissimus muscle depth and backfat thickness assessment was performed. Blood was also collected every 10 days from days 113 to 323 for puberty evaluation via plasma progesterone. Liver and subcutaneous fat biopsies were performed on days 51, 111, 261 and 325. Average daily gain was greater (P<0.01) for MI than CON from day 1 to 51, tended (P=0.09) to be greater for CON than MI from day 112 to 326, while BW on day 326 was similar between treatments. On day 51, MI had greater (P⩽0.01) plasma IGF-I and glucose concentrations, as well as mRNA expression of hepatic pyruvate carboxylase and adipose fatty acid synthase than CON. On days 261 and 325, plasma insulin concentrations were greater (P⩽0.03) in CON than MI. Mean mRNA expression of hepatic IGF-I and adipose peroxisome proliferator-activated receptor gamma were greater (P⩽0.05) in MI than CON. No treatment effects were detected for puberty attainment rate. In conclusion, supplementing nursing heifers via creep-feeding for 50 days altered physiological and biochemical variables suggestive of a metabolic imprinting effect, but did not hasten their puberty attainment.

Present-Day Solifluction Processes in the Semi-Arid Range of Sierra Nevada (Spain)

In the highest land of the Sierra Nevada National Park, an experiment to monitor solifluction rates together with the thermal regime of the ground was implemented during the period 2005–2011. Data show evidence of the low activity of solifluction processes in the present-day periglacial belt of Sierra Nevada. Annual displacement rates were lower than 1 cm yr−1 both in northern and southern slopes. Solifluction was more active near snow patches and streams. Rates were also higher during snowier years. Soil temperatures showed seasonal frost occurrence, though the depth and duration of the frozen layer is strongly conditioned by the annual snow cover. Water availability appears to be a crucial factor for solifluction processes in this semiarid environment.

Upper lethal temperatures of Northern Bobwhite embryos and the thermal properties of their eggs

Northern Bobwhite eggs in the southern United States are often exposed to ambient temperatures in excess of their normal incubation temperature when unattended during their typical extended preincubation period. In drought years, typified by high ambient temperatures, Bobwhite eggs are often exposed to temperatures > 45°C, well-above the upper lethal temperature of most other birds. Because the upper lethal temperature of Bobwhite embryos is not currently known, simulated clutches of eggs were exposed to preincubation temperatures ranging from 39 to 52°C for exposure times of 1, 3, or 6 h. The upper lethal temperatures and the temperatures resulting in ≥ 50% death of Northern Bobwhite embryos were recorded in addition to the time to thermal equilibrium of Bobwhite eggs. The upper lethal temperature for 1, 3, and 6 h of preincubation exposure was 51, 49, and 46°C, respectively. The temperatures resulting in ≥ 50% death were 46, 44, and 40°C for eggs exposed to elevated temperatures for 1, 3, and 6 h, respectively. The mean time for the inner-egg temperature to reach the ambient temperature was 38 ± 1 min (± SE). The thermal tolerances of Northern Bobwhite embryos were much higher than expected, and among the highest reported for birds, indicating an adaptation to the naturally occurring temperature extremes that often occur in the Bobwhite's semi-arid southern range. However, as the temperature increased above the incubation temperature, hatching success declined, showing that increased thermal tolerance has a cost. Although Bobwhite producers, managers, and researchers will find this information useful, it seems most interesting that high temperatures could plausibly have contributed to the population decline observed in the Bobwhite's semi-arid range.

Modelling the long-term consequences of undernutrition of cows grazing semiarid

Undernutrition of cows grazing semi-arid range as a result of drought or heavy stocking rates reduces prenatal and pre-weaning growth of their calves. A mechanistic model has been developed that simulates the productivity of vegetation and cattle on semi-arid savanna rangeland in southern Africa. When cows are stocked at 0.200 cows/ha instead of 0.123 cows/ha the model predicted that empty body weights of their progeny at birth and weaning would be reduced by 2.9 and 43.8 kg, respectively. If all young animals are stocked at 0.22 animals/ha after weaning, differences in empty body weight at weaning are predicted to persist almost unchanged for a further two years. The model also predicted that undernutrition of cattle aged 21 months would be followed by partial compensatory growth. Comparison of simulated results with data from experiments in Zimbabwe indicates that the model realistically simulates the effects of stocking rate on cattle growth.

Strategic nutrient supplementation of free-ranging goats

This paper provides an insight to nutritional limitations of forages and other feed resources and the use of supplementation technology by small farmers to optimize production potential of goats in semiarid range environments. In developing countries, the potential for goat meat production is limited by many environmental and nutritional factors. Free-ranging goats can select their diet from a complex variety of available native plant species. Forage quality and availability are reduced during winter and dry seasons of the year, affecting nutrient intake. Furthermore, the presence of plant secondary metabolites (PSM) in shrub species reduces the availability of energy, increasing the demand for glucose. Supplementation is required to mitigate both, nutrient deficiencies and the effect of PSM toxicity. Supplementation options include leguminous fodders that can serve as good protein and energy sources. However, these fodders need to be irrigated for optimum forage production. Cactus, which requires very little water and is frequently used in some developing countries as feed supplement for ruminants during periods of severe drought, has the disadvantage of high fibre and ash contents, and therefore, low energy and protein densities. Supplementation can also include energy sources such as molasses, cereal grains and byproducts, oilseeds and protein meals, minerals and vitamin A. Feed additives such as ionophores and polyethylene glycol (PEG) still need more evaluation under range conditions. Low-level (0.2–0.4% of body weight) cost-efficient high protein and mineral supplements should be considered carefully. Supplementation should be specific, considering the protein content and mineral profiles of forages in each region. Mineral and protein supplementation of goats consuming high fibre-low protein forages, generally improve intake and performance. Hand-crafted multi-nutrient blocks based on molasses and urea, can stimulate rumen fermentation and supply nutrients needed to complement deficiencies of goats consuming low quality forages. These bocks would require certain degree of compaction and the inclusion of lime (calcium oxide) that reacts with molasses will aid in hardness to restrict intake. They can be transported and managed easily and control supplement intake, while reducing the need of salt as intake regulator and the risk of urea toxicity. Technology transfer to producers should emphasis the use of cost effective and specific nutrient supplementation technology to optimize growth and reproduction of range goats.

Abiotic conditions, neighbour interactions, and the distribution of Stipa tenacissima in a semiarid mountain range

Abiotic conditions and interactions among plants are important factors determining plant geographical distributions. With the aim of analyzing the distribution of a perennial grass species in a semiarid mountain range, we experimentally tested above- and belowground effects of shrubs on the grass along a gradient of aridity. We measured growth, physiology and reproductive output of Stipa tenacissima tussocks surrounded by intact or manipulated neighbour shrubs. Performance of Stipa improved under mesic conditions, but the net effect of shrubs on Stipa did not change along the gradient. Belowground, we did not find significant effects, suggesting belowground resource partitioning between tussocks and shrubs. Aboveground net effects of shrubs on Stipa were generally positive and independent from abiotic conditions. The improved performance of Stipa at the mesic end of gradient suggests that its absolute physiological optimum lies out of its realized range. Overall, the arid end of the geographical distribution of Stipa in this mountain range may be determined by environmental severity. The coincidence of the upper limit of Stipa with the lower tree limit suggests that the more mesic end of Stipa distribution may depend on other factors; most likely competition with trees, which, unlike shrubs, could be excluding Stipa tenacissima from forests.

Artefact discard and accumulated patterns in stone artefact assemblage composition in surface archaeological deposits from Pine Point and Langwell Stations, western New South Wales

This paper addresses the potential of deflated surface archaeological deposits to contribute to our understanding of human use of the southern periphery of the semi-arid Barrier Range of western New South Wales. Radiocarbon determinations from heat retainer hearths are used to establish occupational contexts for the surface deposits near the confluence of 2 creeks. This demonstrates a 2000 year discontinuous record of occupation on the eroded surfaces adjacent to the creeks. The reduction and use of raw materials is compared between stone artefact assemblages from these surfaces. The results of the stone artefact analysis indicate both similarities and differences in the formation of the stone artefact assemblages. These patterns are related to the temporal character of human occupation across the landscape. Assemblages that represent a greater intensity of raw material reduction are indicative of extended occupation. The discontinuous occupational chronology from the region suggests that synchronic settlement pattern models underestimate the temporal variation evident in human – environment relationships.

Effect of tree leaf as supplementation on nutrient digestion and rumen fermentation pattern in sheep grazing semi-arid range of India – II

A study was conducted to evaluate the effects of supplementing with different tree leaves on nutrient digestion, rumen fermentation and blood parameters of sheep. Thirty adult Malpura rams (39.0 ± 0.56 kg) were divided into five groups of six each. They were grazed as a single flock on a semi-arid rangeland and after the end of routine grazing period (08:00–17:00 h), first group (G1), which was not provided with any supplementation, served as control group. Second group (G2) was supplemented with 200 g of a conventional concentrate mixture per head per day, whereas third, fourth and fifth groups (G3, G4 and G5) were supplemented with approximately 200 g dry matter (DM) per day freshly cut foliage from Ailanthes excelsa, Azardirachta indica and Bauhinia racemosa, respectively. Protein content (g kg −1 DM) in A. excelsa, A. indica and B. racemosa foliage was 197, 128 and 132, respectively. A. indica and B. racemosa foliages also contained 123.2 and 211.2 g kg −1 DM condensed tannin (CT) with protein precipitating capacity (PPC) of 16.5 and 46.5 g kg −1 DM. None of the tree leaves contained hydrolysable tannin (HT). Dry matter intake (DMI, g day −1) was 591, 766, 865, 974 and 939 in G1, G2, G3, G4 and G5, respectively. Digestible crude protein (DCP) and metabolisable energy (ME) intakes in supplemented groups G2–G5 were higher ( P < 0.05) compared to control (G1). Supplementation improved digestibility of all nutrients in all groups. Rumen fermentation study indicated lower ( P < 0.05) ammonia and total N in the rumen liquor collected from G5 sheep compared to the other supplemented groups. Although haemoglobin (Hb, g dl −1) levels showed small changes among groups, blood urea nitrogen (BUN, mg dl −1) was lowest in G5 compared to the other groups. Initial BW were similar among the groups. After 60 days of experimental feeding, all animals maintained their BW, except sheep in the control group (G1), which lost BW. Results indicate that for adult sheep grazing on a semi-arid range, supplementation with a concentrate mixture could be replaced by tree leaves like A. excelsa, A. indica and B. racemosa, during the lean season to maintain their BW. In addition, supplementing with tree leaves containing condensed tannin has advantages in terms of N utilization.

Effect of feeding tree leaves as supplements on the nutrient digestion and rumen fermentation pattern in sheep grazing on semi-arid range of India – I

A study was carried out to determine the effect of feeding different tree leaves as supplements on nutrient digestion, rumen fermentation and blood parameters of sheep grazing on a semi-arid rangeland. Thirty adult Malpura rams of uniform body weight (39.0 ± 0.75) were divided into five groups of six each. They were grazed as a single flock from 08.00 to 17.00 h on a semi-arid rangeland. After the end of the grazing period, the first group (G1), which was not provided with any supplementation, served as the control. The second group (G2) was supplemented with 200 g of a concentrate mixture per head per day, whereas the third, fourth and fifth groups (G3–G5) were provided with approximately 200 g DM d −1 of freshly cut foliage from Prosopis cineraria, Acacia nilotica and Albezia lebbek. The foliage from P. cineraria contained 133.4 g kg −1 DM condensed tannin (CT) with protein precipitating capacity (PPC) of 66 g kg −1 DM, whereas A. nilotica contained 18.9 g kg −1 DM hydrolysable tannin (HT) with PPC of 11.5 g kg −1 DM. However, A. lebbek did not contain any tannin. The protein contents were 119, 139 and 194 g kg −1 DM, respectively. The DMI (g d −1) was 688, 916, 1024, 1003, 999 in G1, G2, G3, G4 and G5, respectively. Digestible crude protein (DCP) and metabolizable energy (ME) intakes in supplemented groups G2–G5 were higher ( P < 0.05) than in the control (G1). Supplementation improved the DM digestibility in all groups, whereas CP digestibility was lower ( P < 0.05) in G3 compared to G2, G4 and G5. Rumen fermentation study conducted 6 h after supplementation revealed that total N, ammonia N, and total VFA levels were lower ( P < 0.05) in G3 compared to the other supplemented groups. Although the haemoglobin (Hb) levels were similar among groups, blood urea N (BUN) was lowest in G3 compared to the other groups. The initial body weights were similar among groups (mean 39 kg). After 60 days of experimental feeding, all groups maintained their body weight, except the control group (G1), which lost body weight. It was observed, that supplementation with tree leaves containing CT like P. cineraria helps in better rumen fermentation pattern by preventing excessive loss of nitrogen. It was concluded that maximum nutritional benefits of tree leaves could be harvested, if used as supplement rather than as a sole feed.

Effect of season on thermoregulatory responses and energy expenditure of goats on semi-arid range in India

A study of the physiological responses and energy expenditure of goats was carried out from June 1999 to May 2000 by conducting two experiments: one on bucks maintained on stall feeding in autumn 1999 (Expt 1) followed by year-round grazing on native ranges over three seasons: monsoon, winter and summer (Expt 2). Physiological responses and energy expenditure (EE) measurements of housed and grazing goats were recorded at 06.00 h and 14.00 h for 5 consecutive days in each season. Goats were fixed with a face mask and meteorological balloon for collection of expired air and measurement of EE. Respiration rate (RR) at 06.00 h was similar in all seasons (14 respiration/min) except in the monsoon, where a significantly (P&lt;0.05) higher value (26 respiration/min) was recorded. At 14.00 h, RR was higher in monsoon and summer (81 and 91 respiration/min) than in winter (52 respiration/min). Irrespective of the season, heart rate (HR) was higher at 14.00 h (86 beat/min) than at 06.00 h (64 beat/min). The rise of rectal temperature (RT) from morning (06.00 h) to peak daily temperature (14.00 h) was 0.9 °C in housed goats in autumn and 1.0, 2.1 and 2.0 °C in grazing goats during monsoon, winter and summer, respectively. The mean value was 1.7 °C. Skin temperature (ST) was lowest in winter (30.1 °C) and highest at 14.00 h in summer (40.3 °C). Energy expenditure of goats at 06.00 h was 32.7 W in winter and significantly (P&lt;0.05) increased to 52.0 W in summer and 107.8 W in monsoon. At 14.00 h, EE was 140.2 W in winter and increased to 389.0 W and 391.3 W respectively in monsoon and summer. It is concluded that monsoon and summer are both stressful seasons in semi-arid regions. Animals should be protected from direct solar radiation during the hottest hours of the day to ameliorate the effect of heat stress.

Nutrition of Range Goats in a Shrubland of Western India

An investigation was made to evaluate the native range of western India in terms of nutrient supply during different physiological stages in goats. One hundred female and 5 male Kutchi adult goats were grazed on a 35 ha plot of native range. They were maintained on sole grazing. Four experiments, one in a defined physiological stage was carried out. Stage I, when maximum number of females were bred; stage II, when bucks were used for breeding purpose; stage III, 3-months old (weaner) kids were allowed to graze on ranges and stage IV, when the goats were in early stage of lactation. During oestrous period, diet contained 15.2% crude protein (CP), 54.0% neutral detergent fibre (NDF), 31.5% acid detergent fibre (ADF) and 12.6% acid detergent lignin (ADL). Digestibility coefficient of dry matter (DM), CP, NDF and ADF was 0.586,0.531, 0.431 and 0.239, respectively. DM, digestible crude protein (DCP) and metabolizable energy (ME) intakes were 82.7, 6.71 g kg -1 W 0.75 and 0.99 MJ kg -1 W 0.75 . Diet of buck was constituted by 230 g kg -1 DM of grasses and forb and 770 g kg -1 DM of tree foliage. CP, NDF, ADF and ADL contents of the diet were 13.6, 57.8, 43.5 and 20.0%, respectively. DM, DCP and ME intakes were 57.9, 4.13 g kg -1 W 0.75 and 0.82 MJ kg -1 W 0.75 . Digestibility coefficient of CP, NDF and ADF were 0.496, 0.432 and 0.346, respectively. Diet of kids was constituted by Prosopis cineraria (900 g kg -1 DM) and Zizyphus nummularia (l00 g kg -1 DM) leaves. Digestibility of CP, NDF and ADF were 0.456, 0.415 and 0.201, respectively. DM, DCP and ME intakes were 85.8, 6.44 g kg -1 W 0.75 and 1.22 MJ kg -1 W 0.75 . Lactation phase of goat fell between October-December and tree foliage formed the major portion of the diet. Diet of lactating goat contained only 6.8% CP and 16.5% ADL. Digestibility of DM, CP, NDF and ADF was 0.567, 0.221, 0.307 and 0.233, respectively. DM, DCP and ME intakes were 108.2, 1.62 g kg -1 W 0.75 and 1.50 MJ kg -1 W 0.75 , respectively. Present study establishes that goats on semiarid range with sufficient number of fodder trees were able to meet the nutrient requirement of ewes during oestrous and bucks during breeding season. However, during lactation and active growth phase, only DM requirement is met. Thus, it is recommended to supplement concentrate mixture to goats grazing on range during lactation and growth phase. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1719-1724)

Merits of native and introduced Triticeae grasses on semiarid rangelands

Experiments were conducted on four semiarid range sites to compare stand establishment, productivity, and persistence of several introduced perennial Triticeae grasses with that of their native counterparts. On Intermountain sites with severe water limitations (&lt; 300 mm), native grasses were more difficult to establish, less productive, and less persistent than the introduced grasses. Stands of native grasses declined most rapidly under defoliation. At locations where moisture conditions were more favorable, particularly where more summer precipitation occurred, native Triticeae grasses established and persisted relatively well compared with the introduced entries. Although difficult to establish, stands of the rhizomatous native, western wheatgrass [Pascopyrum smithii (Rydb.) A. Löve] in creased during the seasons after establishment. Choice of plant materials to be used in range seeding programs should be based on objective criteria. To do otherwise will perpetuate degradation of soil resources, especially on sites that are dominated by weedy annual species such as cheatgrass (Bromus tectorum) and medusahead rye (Taeniatherum asperum). It is proposed that adapted introduced grasses be equally considered along with native grasses as a component of seed mixtures on environmentally harsh sites that have been burned, infested with competitive weedy species, or otherwise degraded. Key words: Grass breeding, revegetation, introduced grasses, Triticeae, cheatgrass, seedling vigor, plant persistence

Soil moisture evaluation using multi-temporal synthetic aperture radar (SAR) in semiarid rangeland

There have been several efforts to utilize satellite-based synthetic aperture radar (SAR) measurements to determine surface soil moisture (to 5 cm) conditions of rangeland regions. The results have been mixed since the relation between the SAR signal and surface soil moisture is confounded by variations in topographic features, surface roughness and vegetation density. We designed an experiment to investigate the sensitivity of C-band SAR backscatter ( σ 0) to surface soil moisture ( θ s) in a semiarid rangeland and to test a data-fusion approach based on both optical (Landsat TM) and radar (ERS-2 SAR) measurements to improve regional estimates of surface soil moisture content. The data-fusion approach [Sano, E.E. 1997. Sensitivity analysis of C- and Ku-band synthetic aperture radar data to soil moisture content in a semiarid regions. Ph.D. Dissertation. University of Arizona, AZ] utilized the difference between dry- and wet-season SAR σ 0 to normalize roughness effects, and utilized surface reflectance in optical wavelengths to account for differences in vegetation density. We focused the study on three flat, uniformly vegetated sites of known surface roughness, monitored variations in surface soil moisture, vegetation density and SAR signal over time, and obtained eight optical/SAR image pairs throughout the dry and wet seasons. For these sparsely vegetated sites during this dry year (1997), we found that the SAR signal was not significantly attenuated by sparse green vegetation cover ( green leaf area index <0.35 ) and dense standing brown vegetation cover (brown leaf area index up to 1.5). Consequently, the optical data was not required for this application, and the approach could be implemented by simply taking the difference between the dry- and wet-season SAR σ 0 ( σ 0− σ dry 0). For a data set of eight dates at three study sites, we confirmed that the relation between ERS-2 C-band SAR σ 0 and θ s was weak ( r 2=0.27); yet for the same data set, that the relation between σ 0− σ dry 0 and θ s was strong and significant ( r 2=0.93). This study also raised two concerns: (1) the overall sensitivity of SAR σ 0 to θ s was relatively low, and (2) the approach required a high level of accuracy in the estimate of green leaf area level that may not be obtainable with standard optical remote sensing algorithms. In any case, the positive results from this study should encourage the use of a multi-temporal SAR and optical/SAR fusion for monitoring semiarid range conditions, and improving management of scarce resources.

Natural Hybrids of Elymus elymoides × Leymus salinus subsp. salmonis (Poaceae: Triticeae) Kevin B. Jense

Several putative hybrids between Elymus elymoides (Rafin.) Sweezey and Leymus salinus (M.E. Jones) Á. Löve subsp, salmonis (C. Hitchc.) Atkins were found growing on the west side of the Great Salt Lake, near Lakeside, UT in 1995. Naturally occurring hybrids between these two species have not been documented previously. Cytological, morphological, and chloroplast DNA analysis of the hybrids and parents confirmed the hypothesis that these plants were hybrids of the two species. Elymus elymoides and L. salinus subsp. salmonis were the only Triticeae species growing in the area that could have contributed to the intermediate morphological features expressed in the hybrids. Leymus salinus subsp, salmonis (NsNsXmXm; 2n = 4x = 28) and E. elymoides (StStHH; 2n = 4x 28) are allotetraploids that regularly formed 14 bivalents at metaphase I (MI). The hybrids between the two species are also tetraploids and averaged 22.1 univalents and 2.86 bivalent associations per cell at MI. Chromosompea iring in the hybrids suggests essentially no homology between the chromosomes from the two parents; thus the genomic formula for the hybrid can be written as StHNsXm. The hybrids were morphologically intermediate between the suspected parent species, but they resembled L. salinus subsp, salmonis more closely than E. elymoides. Analysis of chloroplast DNA in the hybrid and its putative parents, demonstrates cytoplasmic DNA identical to E. elymoides, suggesting that E. elymoides was the maternal parent. Complete sterility and reduction in chromosome pairing in the natural hybrids between E. elymoides and L. salinus subsp, salmonis suggest that the potential for genetic exchange between the two species is limited or lacking. Due to hybrid sterility, the natural hybrid will have little impact on the native vegetation of the western deserts of Utah and, without restored fertility, has no potential as a restoration grass on semiarid range sites.

Perspective: Animal‐vegetation relations which optimise production, utilisation and protection of natural resources: An African experience

The broad objective is to improve the standard of living of farmers/herders through identification of complementary vegetation-use under mixed animal species grazing. This paper aims to (1) review mixed-grazing research and development carried out in Ireland and in the semi-arid Senegalese Sahel; (2) evaluate results in relation to other grazing lands; and (3) identify research and development strategies for the future with emphasis on Africa. A systems approach is suggested as the best model. The strategy for the semi-arid area is to measure dietary selection by cattle, sheep and goats when grazed separately and mixed, and to select mixes and overall grazing intensities which would satisfy the objectives of combining productive and protective vegetation resource-use. New methodology was developed. Under temperate conditions mixed sheep/steer grazing increased animal growth rate by 7–10% or stocking rate by 13%. Benefits were also obtained using mixtures of suckler cows and sheep and using lambs grazing dairy pastures in early winter. Roundworm burdens in lambs were also reduced. In semi-arid range sheep diets were intermediate between widely differing cattle and goat diets. The herbaceous layer dominated sheep and cattle diets, and woody species the goat diets. Large between-year and season variations occurred. It is necessary to select the correct animal mix and grazing intensity to combine efficient and ecologically balanced use of vegetation. Vegetation dry matter availability was of little use in estimation of pasture value. It appeared that the critical stocking rate or grazing is that which gives the optimum use of the most vulnerable vegetation fraction and for sustainability the application of this to all vegetation fractions. Within-plot vegetation state, dietary origins from a common vegetation menu and patterns of herds and individual animal uses of spatial and temporal variation are essential. Use of mixtures increases options to improve resource use, maintain a more balanced subclimax vegetation and to build improved grazing ecosystems. Keywords: africa; cattle; cattle diets; condition; cows; dairy pastures; dietary selection; dry matter; ecosystems; goats; grazing; grazing ecosystems; grazing intensity; growth rate; herbaceous layer; ireland; lambs; methodology; mixed-species grazing; model; natural resource use; natural resources; pastures; range; senegal; sheep; stocking rate; sustainability; systems approach; temporal variation; vegetation; vegetation use; woody species African Journal of Range & Forage Science , 13(1): pp. 42-48

Overstocking the Range: A Critical Analysis of the Environmental Science of Sahelian Pastoralism

AbstractThere has been little experimental work in West Africa that distinguishes grazing from climate effects on rangeland vegetation. In the absence of such knowledge, the recurrence of boom-bust cycles in livestock populations, along with the seemingly degraded state of semiarid range, have been used to support notions of the inevitability of overgrazing. Regional stocking rates are used as indicators of degradation potential. I argue that the persistent reliance by environmental analysts on carrying-capacity models oversimplifies range ecology and excludes social processes from causal analyses. Both regional stocking rates and the seasonality of livestock distributions should be treated as proximate factors, each affected by biophysical and socioeconomic conditions. The common assumption that the size of local livestock populations is primarily affected by bioclimatic factors results from a misunderstanding of the pastoral economy. A case study examines the underlying causes of the cattle population b...

Growth and nutrition of combinations of native and introduced plants and mycorrhizal fungi in a semiarid range

The symbiotic responses of native and introduced plant-fungus combinations were determined Indian ricegrass ( Oryzopsis hymenoides (R.&S.) Ricker) and crested wheatgrass ( Agropyron desertorum (Fisch.) Schult.) were pre-inoculated with an introduced fungus, three native fungi, or a mixed native inoculum (VAM plants), and transplanted to fumigated field plots on a semiarid range in western Nevada. Non-fumigated and fumigated plots with non-VAM plants were used as controls. No treatment produced significant plant growth responses relative to controls. Crested wheatgrass generally had the lowest levels of VAM fungal colonization, yet the highest levels of nutrient uptake when compared with Indian ricegrass. Differences in nutrient concentrations, but not contents, were significant among fungal inoculum treatments. Glomus pallidum increased N shoot concentrations above the fumigated control levels for both Indian ricegrass and crested wheatgrass, and the native Glomus mosseae increased N concentration for Indian ricegrass only. For Indian ricegrass, G. pallidum increased P shoot concentrations above controls. G. mosseae and G. pallidum enhanced the uptake of P when compared with the introduced isolate. The introduced G. mosseae and the native Glomus etunicatum enhanced Mn uptake for Indian ricegrass only. The uptake of N and P were reduced in plants colonized by a mixture of three native isolates when compared with uptake by single native isolates for Indian ricegrass. The lack of a shoot growth effect for Indian ricegrass and crested wheatgrass in the presence of introduced or native VAM fungi suggests that these plants are facultative mycotrophs. Mycorrhizae appear to facilitate luxury consumption of nutrients by these grasses, which may be an important adaptation in nutrient-poor desert environments. Further knowledge of effects by native and introduced VAM fungi, and of host effects on the symbiotic association will contribute to more effective establishment of plants in new areas.

Reproduction of White-Tailed Jackrabbits on Semi-Arid Range

Reproduction in lagomorphs may be sensitive to adverse winter conditions or summer drought. Consequently, I studied white-tailed jackrabbits (Lepus townsendii) in Wyoming, from 1985 to 1987, to evaluate their reproductive pattern and fertility on semi-arid range. The breeding season of white-tailed jackrabbits began between late February and mid-March and ended in july. Breeding began later in 1986 and 1987 (2 yr with sparse snow cover) than in 1985 (when greater late-winter snow accumulation occurred). I detected no effect of ambient temperature on the onset of breeding. Reproductively active females conceived in approximate synchrony, and litters were produced during 3 distinct periods each year