Removal Of Cattle Research Articles

The effects of browsing by feral and re-introduced native herbivores on seedling survivorship in the Australian rangelands

Browsing by introduced cattle (Bos taurus) and rabbits (Oryctolagus cuniculus) can limit the recruitment of some arid zone tree and shrub species. In a study conducted at the Arid Recovery Reserve, Roxby Downs, SA, we aimed to quantify initial recruitment changes in shrubs after the removal of cattle and rabbits and the re-introduction of locally extinct fauna. The presence and abundance of seedlings was measured at groves of seven native perennial shrubs over 6 years under four browsing treatments: (1) ‘reserve-reintroductions’ [re-introduced greater stick-nest rats (Leporillus conditor), burrowing bettongs (Bettongia lesueur) and greater bilbies (Macrotis lagotis)], (2) ‘reserve-no browsers’, (3) ‘pastoral-stocked’ (rabbits and cattle), and (4) ‘pastoral-destocked’ (rabbits). Recruitment of mulga (Acacia aneura F.Muell. ex Benth.), silver cassia (Senna artemisioides subsp. petiolaris Randell) and sandhill wattle (Acacia ligulata A.Cunn. ex Benth.) was significantly greater in the two browsing regimes inside the Reserve than in the two pastoral regimes. The number of recruits of these three species declined at ‘pastoral-destocked’ and ‘pastoral-stocked’ sites but increased at ‘reserve-reintroductions’ and ‘reserve-no browsers’ sites from 2001 to 2006. Narrow-leaf hopbush (Dodonaea viscose (L.) Jacq.) showed a trend towards increased recruitment at sites in both browsing regimes inside the Reserve, but decreased recruitment at sites in both pastoral regimes. Native plum (Santalum lanceolatum R.Br.), native apricot (Pittosporum phylliraeoides orth. var. DC.) and bullock bush (Alectryon oleifolius (Desf.) S.T.Reynolds) exhibited no significant difference in recruitment between the four browsing regimes within the study timeframe. These results suggest that excluding rabbits and stock may benefit the germination and survival of mulga, silver cassia and sandhill wattle. To date, re-introduced native herbivores at low numbers have not been found to negatively affect the recruitment or growth rate of the seven perennial plant species studied.

Forest Regeneration from Pasture in the Dry Tropics of Panama: Effects of Cattle, Exotic Grass, and Forested Riparia

Abstract We currently have the opportunity to restore one of the most threatened tropical ecosystems on the Pacific coast of Panama as a consequence of land use change. Factors that influence succession must be understood in order to capitalize on natural regeneration mechanisms. In this study, we determined the effects of exotic grass removal, cattle removal, proximity to forested riparian zones, and topography (upslope vs. downslope) on the initial stages of forest regeneration from pasture in a dry tropical region. After 3 years, basal area, stem density, and species richness of plants (trees, shrubs, vines, and herbs) were significantly and positively affected by exclusion of cattle, presence of exotic grass (no herbicide application), and presence of adjacent forested riparian zones (p < 0.01). Interactions between factors were not significant. Cattle foraged and stomped on vegetation, whereas herbicide application, although effectively removing grass, also killed tree and shrub sprouts, the major source of regrowth. Proximity to forested riparian zones had the greatest effect on species diversity. Shannon’s index for diversity (H) equaled 3.23 in plots adjacent to forested riparian zones as compared to 2.78 in plots not associated with these areas. Our recommendations during the early stages of forest succession are to (1) exclude cattle, (2) make site‐specific decisions about herbicide application based on the presence or absence of forested riparia and prevalence of coppicing, and (3) actively conserve and protect riparian zones, which function as a critical source of diverse propagules.

Farm Factors Associated with Reducing Cryptosporidium Loading in Storm Runoff from Dairies

A systems approach was used to evaluate environmental loading of Cryptosporidium oocysts on five coastal dairies in California. One aspect of the study was to determine Cryptosporidium oocyst concentrations and loads for 350 storm runoff samples from dairy high use areas collected over two storm seasons. Selected farm factors and beneficial management practices (BMPs) associated with reducing the Cryptosporidium load in storm runoff were assessed. Using immunomagnetic separation (IMS) with direct fluorescent antibody (DFA) analysis, Cryptosporidium oocysts were detected on four of the five farms and in 21% of storm runoff samples overall. Oocysts were detected in 59% of runoff samples collected near cattle less than 2 mo old, while 10% of runoff samples collected near cattle over 6 mo old were positive. Factors associated with environmental loading of Cryptosporidium oocysts included cattle age class, 24 h precipitation, and cumulative seasonal precipitation, but not percent slope, lot acreage, cattle stocking number, or cattle density. Vegetated buffer strips and straw mulch application significantly reduced the protozoal concentrations and loads in storm runoff, while cattle exclusion and removal of manure did not. The study findings suggest that BMPs such as vegetated buffer strips and straw mulch application, especially when placed near calf areas, will reduce environmental loading of fecal protozoa and improve stormwater quality. These findings are assisting working dairies in their efforts to improve farm and ecosystem health along the California coast.

Appraisal of interpretation criteria for the comparative intradermal tuberculin test for diagnosis of tuberculosis in cattle in central Ethiopia.

Accurate detection and removal of infected cattle, using immunodiagnostic tests such as the comparative intradermal tuberculin (CIDT) test, are the basis of control strategies for bovine tuberculosis (TB). According to the Office des Internationale Epizooties recommendation, the cutoff point for positivity of the CIDT test, calculated as the difference between skin thicknesses after bovine tuberculin (B) and avian tuberculin (A) injections (B - A), is >4 mm. This cutoff point is used worldwide, although it is likely that local conditions influence test performance. Thus, this study was formulated to determine CIDT test cutoff points applicable to cattle in central Ethiopia. Receiver operating characteristic analysis was performed for the CIDT test, using data from 186 Bos indicus (zebu) and Bos taurus (Holstein) cattle. Detailed postmortem examination for the presence of TB lesions was used to define disease status. At a cutoff of >2 mm, CIDT test sensitivity was 69% (95% confidence interval [95% CI], 58.5 to 79%), while it was 59% (95% CI, 49 to 69%) at a cutoff of >4 mm. In contrast, specificities of the CIDT test at these two cutoff values were identical, at 97% (95% CI, 89 to 100%). Thus, the maximum sensitivity of the CIDT test can be realized using a >2-mm cutoff without affecting specificity. The apparent prevalence was significantly (chi(2) = 13.56; P < 0.001) higher at a cutoff of >2 mm (16.0%; n = 5,424) than at a >4-mm cutoff (13.5%; n = 5,424). Nonetheless, no significant difference (chi(2) = 2.15; P = 0.14) in true prevalence was observed at a cutoff of >2 mm (19.6%) and at a cutoff of >4 mm (18.5%). Thus, our study demonstrates the importance of defining local, relevant cutoff values to maximize test sensitivity, and we suggest the application of the >2-mm cutoff for testing of cattle in central Ethiopia.

The Policy of Reduction of Cattle Populations from Protected Areas: A Case Study from Buxa Tiger Reserve, India

In India, as elsewhere, protected areas (PAs) have permanent resident populations who are historically dependent on forest resources for their livelihood. The Buxa Tiger Reserve (BTR), in the northern part of West Bengal, is one such reserve forest where villagers have been residing for more than a 100 years. With the creation of a national park, employment opportunities for the forest villagers, who were once treated as an important labour force during the commercial forestry regime, have drastically declined. To reduce pressure on forest resources at the BTR, the World Bank financed India Ecodevelopment Project (IEDP) was initiated with the aim to involve local people by supporting sustainable alternative income­generating activities. In consonance with the dominant view that livestock grazing in bio-diverse regions is destructive to nature, reduction in cattle populations and stall feeding of cattle have been included as reciprocal commitments under this project. This paper is an attempt to assess whether the strategy of cat­tle reduction is really possible. It also tries to explore how far a reduction of cattle is acceptable or feasi­ble in the context of present findings, especially in India. Results show that there is little impact on cattle populations after the project intervention. However, the slow but consistently decreasing trend in cattle populations is evident for other reasons. This article argues that as cattle are an integral part of the rural economy for marginalised groups in PAs like the BTR, where alternative employment opportunities are very limited, the reduction or removal of cattle may not be a viable option as it will adversely affect the livelihood of these vulnerable communities. A more pragmatic approach of rotational grazing would be fruitful for preservation of protected forest areas in countries like India.

Bovine Viral Diarrhea Viruses (BVDV) in Beef Breeding Herds and Feedlots

Bovine viral diarrhea viruses (BVDV) represent significant pathogens in cattle affecting several organ systems, particularly involving the respiratory tract and fetal infections. The principal reservoir of BVDV is the persistently infected (Pl) animal. The PI cattle are born to susceptible heifers/cows exposed during pregnancy, carried to term, and are lifetime shedders of the virus. Current control programs focus on biosecurity using testing of new additions including calves born to negative dams, isolation of new animals until testing completed, and vaccination. Identification by testing and removal of PI cattle are critical to control programs. PI cattle may expose susceptible breeding females resulting in more PI calves; and/or cause primary infections in acute/transient infections and predispose the BVDV exposed animal to other pathogens. The purpose of this study was: (1) detect PI cattle in beef breeding herds and cattle entering feedlots; and (2) determine distribution of BVDV subtypes in PI cattle.

Relationship of First Hollow Stem and Heading in Winter Wheat

The majority of wheat (Triticum aestivum L.) in the southern Great Plains is produced as a dual‐purpose crop enterprise. Profitability of the system is highly dependent on removal of cattle (Bos taurus L.) from wheat pastures at the first‐hollow‐stem stage of growth. A previous survey implied that earliness of first hollow stem and earliness of heading are independent traits, which would allow a grower to select a cultivar with late first hollow stem without sacrificing early maturity. We evaluated first hollow stem and heading records for 52 hard winter wheat lines (49 commercially available winter wheat cultivars and three advanced experimental lines) during a 7‐yr period at Stillwater, OK. Our analysis shows a positive, linear relationship between the occurrence of first hollow stem and heading in wheat when these phenological events were expressed as a function of cumulative thermal units after 1 January. When expressed in terms of calendar date, however, intervals between the earliest and latest cultivars for the first‐hollow‐stem stage were much greater than those for heading date. Overall, our analysis indicates that among commercially available cultivars and advanced experimental lines, choosing a cultivar with later occurrence of first hollow stem will also result in later heading in the same given environment.

Savanna herbivore dynamics in a livestock-dominated landscape. II: Ecological, conservation, and management implications of predator restoration

Conserving African wildlife in human-occupied landscapes requires management intervention that is guided by a mechanistic understanding of how anthropogenic factors influence large-scale ecological processes. In Laikipia District, a dry savanna region in northern Kenya where wildlife share the landscape with humans and livestock, we examined why five of nine wild ungulate species suffered protracted declines on properties receiving the greatest conservation investment. Of 10 alternative causes examined, only an increase in predation, interacting with brief periods of high and low rainfall, was consistent with the timing, synchrony, duration and species composition of observed ungulate declines. The principal factor causing predation to increase was a shift in land use from cattle ranching, under which predators and plains zebras were severely suppressed, to wildlife conservation and ecotourism. This prompted a 5-fold increase in plains zebra abundance, and created a demand for living predators. Plains zebras ultimately comprised more than half the available prey biomass, and supported a substantial predator community, but were not limited by predators. We infer that increasing predation pressure caused predator-susceptible prey species to decline, via mechanisms that included apparent competition. Herbivore dynamics in Laikipia shared features with previously reported responses by prey communities to predator manipulation in Kruger and Serengeti National Parks. All featured one or a few numerically dominant herbivore species, which were primarily limited by rainfall and density, supporting a predator community that in turn limited the abundance of other prey species. In each case, predation had a profound effect, but on only a subset of prey species, reducing the evenness component of prey diversity. The presence of cattle in the landscape may affect predator–prey dynamics in both direct and indirect ways, depending on rainfall. In extreme years (floods or drought), episodic die-offs temporarily subsidize scavenging predators. In low rainfall years, competition between plains zebras and cattle, which negligibly support predators, may indirectly limit predator carrying capacity. Consequently, removal of cattle may favor not only zebras, but also their predators, and further depress predator-susceptible prey species.

Integrating Ranch Forage Production, Cattle Performance, and Economics in Ranch Management Systems for Southern Florida

The presence of grazing cattle near open waterways has created environmental concerns related to the potential for water contamination. In Florida the removal of cattle from grazing landscapes or decreasing stocking density is being investigated as one option to improve the quality of surface water runoff draining into Lake Okeechobee, Florida. The objective of this study was to determine the effects of stocking rate on cow-calf performance, forage availability and quality, and ranch economic performance. Experimental pastures were established on a southern Florida cow-calf operation with stocking rates of 0.58, 1.01, and 1.35 ha·cow -1 on summer pastures and 0.93, 1.62, and 2.16 ha·cow -1 on winter pastures, corresponding to high, medium, and low rates, respectively. The study was conducted over 4 consecutive production years. Cow body condition scores (BCS), pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside and outside grazing exclusion cages and forage quality by crude protein and in vitro organic matter digestibility . Forage yield, utilization, and quality were not significantly affected by stocking rate. Although statistically not significant ( P = 0.17), cattle in the high stocking rate experienced a numerically greater loss of BCS following the winter grazing period, but stocking rate did not affect pregnancy rate or calf gains. Production (kg weaned calves·ha -1 ) was increased ( P < 0.01) for a high stocking rate compared with medium and low stocking rates. Overall ranch profitability will decrease as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch's fixed cost structure. La presencia de ganado apacentando cerca de las vías acuáticas ha creado una preocupación ambiental relacionada con el potencial de contaminación del agua. En Florida, la remoción del ganado de los pastizales o la disminución de la densidad de carga animal están siendo investigadas como una opción para mejorar la calidad del agua del escurrimiento superficial que drena en el lago Okeechobee en Florida. El objetivo de este estudio fue determinar los efectos de la carga animal en el comportamiento productivo del binomio vaca-becerro, la disponibilidad y calidad del forraje y los aspectos económicos del rancho. Las praderas experimentales se establecieron en el sur de Florida en un rancho dedicado al sistema vaca-becerro con cargas animal de 0.58, 1.01, y 1.35 ha·vaca -1 para las praderas de verano y de 0.93, 1.62, y 2.16 ha·vaca -1 para las praderas de invierno, que corresponden a cargas alta, media y baja respectivamente. El estudio se condujo durante cuatro años productivos consecutivos. La clasificación de la condición corporal (BCS), tasa de preñez y las ganancias de peso diarias promedio de los becerros se usaron como medidas del comportamiento animal. La utilización del forraje fue estimada midiendo la diferencia entre el rendimiento de forraje dentro y fuera de jaulas de exclusión y la calidad del forraje determinando la proteína cruda y la digestibilidad in vitro de la materia orgánica. El rendimiento de forraje, la utilización y calidad no fueron afectadas significativamente por la carga animal. Aunque estadísticamente las diferencias no fueron significativas ( P = 0.17), el ganado en la carga alta experimentó una pérdida numéricamente mayor de la condición corporal después periodo de apacentamiento en invierno, pero la carga animal no afectó la tasa de preñez o la ganancia de peso de los becerros. La producción (kg de becerro destetado·ha -1 ) se incrementó ( P < 0.01) en la carga animal alta en comparación con las cargas media y baja. La rentabilidad global del rancho decrecerá conforme la carga animal disminuye. Los ingresos del rancho disminuyen al uno por uno conforme la carga animal disminuye. Al mismo tiempo, los costos unitarios por vaca se incrementan al aumentar la carga y conforme una pocas vacas con cría son dejadas para soportar la estructura fija de costos del rancho.

Impact of Grazing Intensity during Drought in an Arizona Grassland

The ecological benefits of changing cattle grazing practices in the western United States remain controversial, due in part to a lack of experimentation. In 1997 we initiated an experimental study of two rangeland alternatives, cattle removal and high-impact grazing, and compared grassland community responses with those with more conventional, moderate grazing practices. The study was conducted in a high-elevation, semiarid grassland near Flagstaff, Arizona (U.S.A.). We conducted annual plant surveys of modified Whittaker plots for 8 years and examined plant composition shifts among treatments and years. High-impact grazing had strong directional effects that led to a decline in perennial forb cover and an increase in annual plants, particularly the exotic cheatgrass (Bromus tectorum L.). A twofold increase in plant cover by exotic species followed a severe drought in the sixth year of the study, and this increase was greatest in the high-impact grazing plots, where native cover declined by one-half. Cattle removal resulted in little increase in native plant cover and reduced plant species richness relative to the moderate grazing control. Our results suggest that some intermediate level of cattle grazing may maintain greater levels of native plant diversity than the alternatives of cattle removal or high-density, short-duration grazing practices. Furthermore, episodic drought interacts with cattle grazing, leading to infrequent, but biologically important shifts in plant communities. Our results demonstrate the importance of climatic variation in determining ecological effects of grazing practices, and we recommend improving conservation efforts in arid rangelands by developing management plans that anticipate this variation.

Culling and cattle controls influence tuberculosis risk for badgers.

Human and livestock diseases can be difficult to control where infection persists in wildlife populations. In Britain, European badgers (Meles meles) are implicated in transmitting Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), to cattle. Badger culling has therefore been a component of British TB control policy for many years. However, large-scale field trials have recently shown that badger culling has the capacity to cause both increases and decreases in cattle TB incidence. Here, we show that repeated badger culling in the same area is associated with increasing prevalence of M. bovis infection in badgers, especially where landscape features allow badgers from neighboring land to recolonize culled areas. This impact on prevalence in badgers might reduce the beneficial effects of culling on cattle TB incidence, and could contribute to the detrimental effects that have been observed. Additionally, we show that suspension of cattle TB controls during a nationwide epidemic of foot and mouth disease, which substantially delayed removal of TB-affected cattle, was associated with a widespread increase in the prevalence of M. bovis infection in badgers. This pattern suggests that infection may be transmitted from cattle to badgers, as well as vice versa. Clearly, disease control measures aimed at either host species may have unintended consequences for transmission, both within and between species. Our findings highlight the need for policymakers to consider multiple transmission routes when managing multihost pathogens.

Escherichia coliO157:H7 andSalmonellain Water and Soil from Tall Fescue Paddocks

Six 1-ha paddocks of tall fescue (Festuca arundinacea) grazed by Gelbvieh x Angus heifers from 1 March to 21 June 2005 were used to determine the prevalence of Escherichia coli O157:H7 and Salmonella in water tanks, and standing water and surface soil surrounding water tanks in tall fescue paddocks grazed by cattle. Paddocks included two each of Kentucky-31 endophyte-infected tall fescue (E+), Jesup tall fescue with the AR542 endophyte strain (MaxQ), and HiMag tall fescue with strain 4 endophyte (HiMag4). Samples were collected weekly (6 June to 5 July) from water tanks (n = 30), and standing water (n = 18) and surface soil (n = 30) surrounding the water tanks in each paddock commencing 3 weeks prior to termination of grazing until 2 weeks after cattle removal. Prevalence of E. coli O157:H7 tended (p = 0.07) to be increased in standing water and surface soil surrounding water tanks when cattle were present. Presence of cattle resulted in muddy conditions surrounding water tanks. Consumption of E+ tall fescue did not influence (p > 0.10) the prevalence of E. coli O157:H7 or Salmonella in or around water tanks. Neither E. coli O157:H7 or Salmonella were detected in water tanks. Total percentage of standing water samples positive for E. coli O157:H7 was 27.8% and 5.6% for Salmonella. Escherichia coli O157:H7 (6.7%) and Salmonella (10%) also were detected in the surface soil surrounding the water tanks. We conclude that areas surrounding water tanks in tall fescue paddocks can be reservoirs of pathogenic bacteria.

Bovine Viral Diarrhea Viruses (BVDV) in the Feedlot

Bovine viral diarrhea viruses (BVDV) represent significant pathogens for cattle. The BVDV affect several organ systems; however, the respiratory tract and fetal infections receive critical attention based on disease impact and potential for reservoirs/transmission. BVDV may cause primary infection of the respiratory tract and also serve to predispose the infected bovine to bacterial pathogens such as Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Archanobacterium pyogenes and Mycoplasma spp. Calves infected in utero and born persistently infected (PI) are important reservoirs of infection as they are life-long shedders of virus to susceptible cattle. Respiratory diseases in the feedlot are significant based on morbidity mortality and economic losses. Detection and removal of PI cattle could potentially lessen the economic effect of BVDV in the feedlot. Also, current BVDV control programs utilize vaccines in the US, primarily those containing BVDV1a and BVDV2a strains. Research at our institution has shown that the BVDV1b subgenotype is the major BVDV strain in our diagnostic laboratory accessions. The purpose of this study was three-fold: (1) determine prevalence of PI cattle entering a feedlot; (2) to utilize and compare various diagnostic tests to identify PI cattle; and (3) to determine the distribution of the BVDV1a, BVDV1b and BVDV2a subgenotypes in PI cattle entering the feedlot.

Seedling survival and growth of native tree species in pastures: Implications for dry tropical forest rehabilitation in central Panama

Our study tested the effects of herbicide application and cattle removal on the survival and growth of three native tree species planted in pastures within a deforested, dry tropical region of Panama. We investigated whether enrichment planting may be a potential, complementing reforestation tool with natural regeneration. Three economically valuable tree species were chosen for the study; Cedrela odorata L., Enterolobium cyclocarpum (Jacq.) Griseb, and Copaifera aromatica Dwyer. Planted seedlings were monitored for survival, root collar diameter and height growth in the presence or absence of two factors; (1) initial herbicide application and (2) cattle. After 16 months, subsamples of seedlings within each treatment were harvested and measured for dry masses and leaf areas. In the initial stages of development, C. odorata seedlings had the greatest growth rates with herbicide application whereas E. cyclocarpum seedlings had the greatest growth rates with cattle exclusion. The combination of these two factors yielded the best growth for both species. Of the three species, C. odorata had the lowest mortality rates (58%), and the greatest average dry mass ( μ = 403.7 g), leaf area ( μ = 169.3 m 2), diameter growth rate ( μ = 3.7 cm year −1) and height growth rate ( μ = 81.7 cm year −1) at 16 months. In addition, in the presence of cattle, C. odorata grew significantly better than E. cyclocarpum. To accelerate forest succession, herbicide should be applied initially and cattle removed before enrichment planting.

Concentrations of fecal bacteria and nutrients in soil surrounding round-bale feeding sites1,2

An experiment was conducted over 7 mo (January to July 2003) to evaluate fecal bacteria and nutrient concentrations in soil surrounding round-bale feeders at 10 winter feeding sites. Soil samples 15 cm in depth were taken monthly from each site at distances of 3, 12, 21, and 30 m from the feeder. Soil samples were taken before livestock access to the sites (January), during the feeding period (February, March, and April), and after cattle removal from the sites (May, June, and July). Results indicated that fecal bacteria concentrations increased over the feeding period and were greatest at close proximity to round-bale feeders. Fecal Escherichia coli concentrations were greater in April (P < 0.03) at 3 and 12 m than in all other months, except March. At 21 and 30 m from the feeders, fecal E. coli concentrations were greater in April (P < 0.01) than in other months. At 3 m from the feeder, fecal Streptococci concentrations were greater in March and April (P < 0.01) than in other months. Although fecal E. coli concentrations in July had returned to levels similar to those in the prefeeding period, fecal Streptococci remained at higher concentrations (P < 0.05) than at the prefeeding period. The concentration of soil P at 3 m was greater in April (P < 0.02) than in January, February, and May. After cattle access to the sites, soil DM content was consistently less for samples taken at 3 m from the feeder compared with the other distances, with quadratic decreases (P < 0.02) noted in March, April, and July, and linear decreases (P < 0.01) in May and June, as distance from the feeder decreased.

The implications for paleodietary and paleoclimatic reconstructions of intrapopulation variability in the oxygen and carbon isotopes of teeth from modern feral horses

We analyzed the isotopic patterns found in the tooth enamel of modern feral horses from Shackleford Banks, North Carolina (USA), which has a temperate climate and supports primarily C 4 grasslands. Enamel δ 13C values averaged −4.1‰ with a standard deviation (1σ) of 1.7‰, which corresponds to an average diet of 66 ± 12% C 4 plants. Our results differ from dietary reconstructions from 1978 to 1981, which found that horses consumed 91% C 4 plants. This suggests that horses have increased their consumption of C 3 forbs, likely as a result of the removal of cattle, sheep, and goats from the island. Shackleford surface waters had δ 18O values that averaged −3.3 ± 0.5‰ and −1.3 ± 1.8‰ on the western and eastern ends of the island, respectively. Tooth enamel samples averaged 27.3 ± 1.5‰ and displayed the same range of δ 18O values as surface waters. The variability of both δ 18O and the δ 13C values among individuals within this population demonstrates that horses from relatively homogenous temperate environments can display a wide range of isotopic values. Given the observed range of isotopic values for modern horses, we suggest that researchers use the mean values of multiple (≥9) equids when attempting to reconstruct average paleodiets and/or paleoenvironmental conditions.

Vegetation Cover and Forb Responses to Cattle Exclusion: Implications for Pronghorn

Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understandtheeffectsofcattlegrazing,westudiedthepotentialhidingcoverprovidedbystandingliveanddeadherbaceousmatter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P ¼ 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P ¼ 0.105) or 25 m (P ¼ 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P ¼ 0.036), but no differences were observed in 2002 (P ¼ 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.

Vegetation Cover and Forb Responses to Cattle Exclusion: Implications for Pronghorn

Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understand the effects of cattle grazing, we studied the potential hiding cover provided by standing live and dead herbaceous matter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P = 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P = 0.105) or 25 m (P = 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P = 0.036), but no differences were observed in 2002 (P = 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.

Bovine viral diarrhoea, bovine herpesvirus and parainfluenza-3 virus infection in three cattle herds in Egypt in 2000.

This study reported field outbreaks of bovine viral diarrhoea virus (BVDV) infection, either alone or mixed with bovine herpesvirus-1 (BHV-1) and/or parainfluenza-3 virus (PI-3V) in Egypt during 2000. In Lower Egypt, young calves in three cattle herds in El-Minufiya Province, El-Fayoum Province and in governmental quarantine in El-Behira Province, showed symptoms of enteritis, either alone or accompanied by respiratory manifestations. The affected herds were visited and the diseased animals were clinically examined. Many epidemiological aspects, such as morbidities, mortalities and case fatalities, as well as the abortive rate, were calculated. Ethylenediamine tetra-acetic acid-blood samples, sterile nasal swabs and serum samples were obtained for virological and serological diagnosis. The laboratory investigations revealed that the main cause of calf mortalities in the three herds was infection with BVDV, either alone, as on the El-Minufiya farm, or mixed with PI-3V, as on the El-Fayoum farm, or mixed with both BHV-1 and PI-3V, as in the herd in governmental quarantine in El-Behira Province. A total of nine dead calves from the three herds were submitted for thorough post-mortem examination. Tissue samples from recently dead calves were obtained for immunohistochemical and histopathological studies. The most prominent histopathological findings were massive degeneration, necrosis and erosions of the lining epithelium of the alimentary tract. Most of the lymphoreticular organs were depleted of lymphocytes. In pneumonic cases, bronchopneumonia and atypical interstitial pneumonia were evident. The present study suggested that the immunosuppressive effect of BVDV had predisposed the animals to secondary infection with BHV-1 and PI-3V. This study concluded that concurrent infection with BVDV, BHV-1 and PI-3V should be considered as one of the infectious causes of pneumoenteritis and, subsequently, the high morbidities and mortalities among young calves in Egypt. Preventive and control measures against these infectious agents should therefore be adopted. All animals imported into Egypt should be free from BVDV infection. Control programmes for the detection and removal of BVDV-persistent cattle should be applied in cattle herds all over the country.

Response of Vegetation and Breeding Birds to the Removal of Cattle on the San Pedro River, Arizona (U.S.A.)

Abstract:In late 1987 cattle were removed from the San Pedro Riparian National Conservation Area ( NCA ) in southeastern Arizona ( U.S.A. ). We monitored vegetation density and abundance of birds during the breeding season during 1986–1990 in riparian, mesquite grassland, and Chihuahuan desert‐scrub communities in the NCA. The density of herbaceous vegetation increased four‐ to six‐fold in riparian and mesquite grassland communities. Little change occurred in herbaceous vegetation in desert scrub, or in the density of shrubs or trees in any of the communities. Of 61 bird species for which sufficient data were collected, mean detections per kilometer increased for 42 species, 26 significantly, and decreased for 19 species, 8 significantly. The number of individuals of all avian species detected on surveys increased each year from 103/kilometer in 1986 to 221/kilometer in 1991, an average annual increase of 23% ( p&lt; 0.001 ). The largest increases occurred in riparian species, open‐cup nesters, Neotropical migrants, and insectivores. Species of the Chihuahuan desert‐scrub, in which vegetation changed the least, showed the smallest increases. Only a few of the species showed increasing regional trends for the same period, as demonstrated by the North American Breeding Bird Survey; thus, increases on the San Pedro Riparian NCA were likely caused by the change in local conditions, not by regional effects. Our results suggest that removing cattle from riparian areas in the southwestern United States can have profound benefits for breeding birds.