33 results on '"Hewitt DG"'
Search Results
2. Oxidation of alkoxyphenols. XX. Ring cleavage and lactone formation in the oxidation of a biphenyl-2,2'-diol by lead tetraacetate.
- Author
-
Hewgill, FR, Hewitt, DG, Howie, GB, and Spencer, WL
- Abstract
Two products in the lead tetraacetate oxidation of 3,3?-di-t-butyl- 5,5?-dimethoxybiphenyl-2,2?-diol have been shown to be (E)-7-t-butyl-5- methoxy-3-[(E)-2?-methoxy-5?,5?-dimethyl-4?-oxohex-2?- enylidenelbenzofuran-2(3H)-one (1) and its (Z,Z) isomer (3). Treatment of these with base causes rearrangement to (E)-8-t-butyl-2-(3?,3?- dimethyl-2?-oxobutylidene)-6-methoxy-2H-1-benzopyran-4-carboxylic acid (13). Further treatment with base produces pinacolone and 8-t-butyl-6- methoxy-2-oxo-2H-1-benzopyran-4-carboxylic acid (14). The latter has been synthesized from 2-t-butyl-4-methoxyphenol via 7-t-butyl-5- methoxy-2,3-dihydrobenzofuran-2,3-dione (15).
- Published
- 1977
- Full Text
- View/download PDF
3. Regioselective Synthesis of Secondary Allyl Chlorides
- Author
-
Boughdady, NM, Chynoweth, KR, and Hewitt, DG
- Abstract
We have developed high-yielding regiospecific conversions of internal secondary allylic alcohols into rearranged or unrearranged allylic chlorides using thionyl chloride in ether at -70C or hexachloroacetone /triphenylphosphine at - 70C respectively. The mechanisms of the reactions are discussed.
- Published
- 1987
- Full Text
- View/download PDF
4. Crystal structure of 2,4-di-t-butyl-6-(3,5-di-t-butyl-2-hydroxyphenyl)-6-morpholinocyclohexa-2,4-dienone.
- Author
-
Hall, SR, Hewitt, DG, Raston, CL, and White, AH
- Abstract
The crystal structure of the title compound, C32H49NO3, has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.061 for 1721 ?observed? re- flections. Crystals are orthorhombic, Pcab, a 18.63(2), b 18.58(2), c 18.19(2) Ǻ, Z 8. The structure determination confirms that proposed on chemical grounds and shows an unusual t-butyl N.M.R. chemical shift to be a consequence of an unusual orientation.
- Published
- 1978
- Full Text
- View/download PDF
5. Organophosphorus compounds. P-Arylated perhydro-1,2-azaphosphorines.
- Author
-
Hewitt, DG and Newland, GL
- Abstract
Treatment of ethyl 4-bromobutylphosphonochloridate with phenylmagnesium bromide, followed by acid-catalysed hydrolysis of the product, gave 4- bromobutyl(phenyl)phosphinic acid. This was converted into the corresponding phosphinamide by treatment with thionyl chloride and then with aqueous ammonia. Cyclodehydrobromination with sodium hydride in warm xylene then gave a good yield of 2-phenylperhydro-1,2- azaphosphorine 2-oxide. Some other routes to this compound were investigated.
- Published
- 1977
- Full Text
- View/download PDF
6. Organophosphorus chemistry. IV. Synthesis and reactions of 2-Ethoxy-6-oxo-1,2-azaphosphinane 2-oxide
- Author
-
Hewitt, DG and Teese, MW
- Abstract
2-Ethoxy-6-oxo-1,2-azaphosphinane 2-oxide (3) has been prepared by cyclocondensation of ethyl 4-(P-amino-P-ethoxyphosphinoyl)butanoate (17). N-Alkylated derivatives of (3) were prepared by cyclocondensation of (17) in the presence of methyl iodide, allyl bromide and benzyl chloride. These derivatives reacted with organometallic reagents and bases to yield acyclic products.
- Published
- 1984
- Full Text
- View/download PDF
7. Organophosphorus chemistry. III. Synthesis of 3-Ethoxy-2-phenyl-1,3-azaphosphininane 3-oxide
- Author
-
Hewitt, DG and Teese, MW
- Abstract
Treatment of ethyl (3-bromopropyl)phosphonochloridate with benzylmagnesium chloride gave ethyl (benzyl)(3-bromopropyl)phosphinate. This underwent free-radical bromination to give ethyl (a-bromobenzyl)(3-bromopropyl)phosphinate Cyclization with aqueous ammonia gave 3-ethoxy- 2-phenyl-1,3-azaphosphininane 3-oxide. Attempts to prepare the 2-(pyridin-3'-yl)-substituted 1,3-azaphosphininane are also discussed.
- Published
- 1984
- Full Text
- View/download PDF
8. Reactions of some halogenocyclohexadienones.
- Author
-
Crozier, RF and Hewitt, DG
- Abstract
Chlorination of 2,4-, 2,6- and 3,5-di-t-butylphenols gave the chlorocyclohexa-dienones (2a), (10), and (7) and (9), respectively. Base-catalysed methanolysis of the ketones (2a) and (9) produced the rearranged gem-dimethoxycyclohexadienones (5)and (11). Under similar conditions the ketone (7) rearranged to 3,5-di-t-butyl-2,4- dichlorophenol, while (10) was converted into a mixture of 2,6-di-t-butyl-1,4-benzo-quinone and 3,5,3',5'-tetra-t-butyl-4,4'-diphenoquinone. The dibromocyclohexa-dienone (2b) also dimerized in the presence of base, affording a low yield of 2,2'-dihydroxy-3,5,3',5'-tetra-t-butylbiphenyl. The mechanisms of these reactions are discussed.
- Published
- 1972
- Full Text
- View/download PDF
9. Nucleophilic replacement of methoxyl in the reaction of a sterically hindered o-benzoquinone with o-phenylenediamine.
- Author
-
Hewgill, FR, Hewitt, DG, and Langley, PB
- Abstract
With o-phenylenediamine, 3-t-butyl-5-methoxy-l,2-benzoquinone gives the quinone imine (VII), but only a trace of the expected phenazine (II). Dilute acid converts (VII) to the anilinophenazine (III). Chemical and spectroscopic evidence for the structures of these compounds is presented.
- Published
- 1965
- Full Text
- View/download PDF
10. Organophosphorus Compounds. II. Ethyl Phenylphosphinate
- Author
-
Hewitt, DG, primary
- Published
- 1979
- Full Text
- View/download PDF
11. Physiological carry-over effects of variable precipitation are mediated by reproductive status in a long-lived ungulate.
- Author
-
Hediger JA, Spencer BD, Rice MF, Hopper ML, DeYoung RW, Ortega-Santos JA, Fulbright TE, Hewitt DG, Foley AM, Schofield LR, Campbell TA, Sheriff MJ, and Cherry MJ
- Abstract
In the age of global climate change, extreme climatic events are expected to increase in frequency and severity. Animals will be forced to cope with these novel stressors in their environment. Glucocorticoids (i.e. 'stress' hormones) facilitate an animal's ability to cope with their environment. To date, most studies involving glucocorticoids focus on the immediate physiological effects of an environmental stressor on an individual, few studies have investigated the long-term physiological impacts of such stressors. Here, we tested the hypothesis that previous exposure to an environmental stressor will impart lasting consequences to an individual's glucocorticoid levels. In semi-arid environments, variable rainfall drives forage availability for herbivores. Reduced seasonal precipitation can present an extreme environmental stressor potentially imparting long-term impacts on an individual's glucocorticoid levels. We examined the effects of rainfall and environmental characteristics (i.e. soil and vegetation attributes) during fawn-rearing (i.e. summer) on subsequent glucocorticoid levels of female white-tailed deer ( Odocoileus virginianus ) in autumn. We captured 124 adult (≥2.5-year-old) female deer via aerial net-gunning during autumn of 2015, 2016 and 2021 across four populations spanning a gradient of environmental characteristics and rainfall in the semi-arid environment of South Texas, USA. We found for every 1 cm decrease in summer rainfall, faecal glucocorticoid levels in autumn increased 6.9%, but only in lactating females. Glucocorticoid levels in non-lactating, female deer were relatively insensitive to environmental conditions. Our study demonstrates the long-lasting effects of environmental stressors on an individual's glucocorticoid levels. A better understanding of the long-term effects stressors impart on an individual's glucocorticoid levels will help to evaluate the totality of the cost of a stressor to an individual's welfare and predict the consequences of future climate scenarios., Competing Interests: The authors have no conflicts of interest to declare., (© The Author(s) 2024. Published by Oxford University Press and the Society for Experimental Biology.)
- Published
- 2024
- Full Text
- View/download PDF
12. Relationships between plant species richness and grazing intensity in a semiarid ecosystem.
- Author
-
Fulbright TE, Ortega-Santos JA, Hines SL, Drabek DJ, Saenz R 3rd, Campbell TA, Hewitt DG, and Wester DB
- Abstract
Plant species richness is an important property of ecosystems that is altered by grazing. In a semiarid environment, we tested the hypotheses that (1) small-scale herbaceous plant species richness declines linearly with increasing grazing intensity by large ungulates, (2) precipitation and percent sand interact with grazing intensity, and (3) response of herbaceous plant species richness to increasing intensity of ungulate grazing varies with patch productivity. During January-March 2012, we randomly allocated 50, 1.5-m × 1.5-m grazing exclosures within each of six 2500 ha study sites across South Texas, USA. We counted the number of herbaceous plant species and harvested vegetation in 0.25-m
2 plots within exclosures (ungrazed control plots) and in the grazed area outside the exclosures (grazed treatment plots) during October-November 2012-2019. We estimated percent use (grazing intensity) based on the difference in herbaceous plant standing crop between control plots and treatment plots. We selected the negative binomial regression model that best explained the relationship between grazing intensity and herbaceous plant species richness using the Schwarz-Bayesian information criterion. After accounting for the positive effect of precipitation and percent sand on herbaceous plant species richness, species richness/0.25 m2 increased slightly from 0% to 30% grazing intensity and then declined with increasing grazing intensity. Linear and quadratic responses of herbaceous plant species richness to increasing grazing intensity were greater for the least productive patches (<15.7 g/0.25 m2 ) than for productive patches (≥15.7 g/0.25 m2 ). Our results followed the pattern predicted by the intermediate disturbance hypothesis model for the effect of grazing intensity on small-scale herbaceous plant species richness., Competing Interests: None declared., (© 2023 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)- Published
- 2023
- Full Text
- View/download PDF
13. Animal use of fence crossings in southwestern rangelands.
- Author
-
Zoromski LD, DeYoung RW, Goolsby JA, Foley AM, Ortega-Santos JA, Hewitt DG, and Campbell TA
- Abstract
Net-wire fencing built to confine livestock is common on rangelands in the Southwestern USA, yet the impacts of livestock fencing on wildlife are largely unknown. Many wildlife species cross beneath fences at defined crossing locations because they prefer to crawl underneath rather than jump over fences. Animals occasionally become entangled jumping or climbing over fences, leading to injury or death. More commonly, repeated crossings under net-wire fencing by large animals lead to fence damage, though the damage is often tolerated by landowners until the openings affect the ability to enclose livestock. The usage, placement, characteristics, and passage rates of fence crossings beneath net-wire fencing are poorly understood. We monitored 20 randomly selected fence crossings on net-wire livestock fencing across two study sites on rangelands in South Texas, USA, from April 2018 to March 2019. We assessed the characteristics of fence-crossing locations (openings beneath the fence created by animals to aid in crossing) and quantified crossing rates and the probability of crossing by all species of animals via trail cameras. We documented 10,889 attempted crossing events, with 58% ( n = 6271) successful. Overall, 15 species of medium- and large-size mammals and turkey ( Meleagris gallopavo ) contributed to crossing events. Crossing locations received 3-4 crossing attempts per day on average, but the number of attempts and probability of successful crossing varied by location and fence condition. The probability of crossing attempts was most consistently influenced by the opening size of the crossing and season; as crossing size (opening) increased, the probability of successful crossing significantly increased for all species. Peaks in crossing activity corresponded with species' daily and seasonal movements and activity. The density and size of fence-crossing locations were dependent on fence maintenance and not associated with vegetation communities or habitat variables. However, crossing locations were often re-established in the same locations after fence repairs. This is one of the few studies to monitor how all animal species present interacted with net-wire livestock fencing in rangelands. Our results will help land managers understand the impact of net-wire livestock fencing on animal movement., Competing Interests: The authors have no conflicts of interest., (© 2022 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)
- Published
- 2022
- Full Text
- View/download PDF
14. EFFICACY OF WHITE-TAILED DEER ( ODOCOILEUS VIRGINIANUS ) TREATMENT FOR CATTLE FEVER TICKS IN SOUTHERN TEXAS, USA.
- Author
-
Currie CR, Hewitt DG, Ortega-S JA, Schuster GL, Campbell TA, Lohmeyer KH, Wester DB, and de León AP
- Subjects
- Acaricides administration & dosage, Acaricides therapeutic use, Administration, Oral, Animals, Antiparasitic Agents administration & dosage, Antiparasitic Agents therapeutic use, Female, Ivermectin administration & dosage, Male, Permethrin administration & dosage, Texas, Tick Infestations drug therapy, Tick Infestations epidemiology, Deer parasitology, Ivermectin therapeutic use, Permethrin therapeutic use, Rhipicephalus, Tick Infestations veterinary
- Abstract
White-tailed deer ( Odocoileus virginianus ) serve as a host for cattle fever ticks ( Rhipicephalus [ Boophilus ] microplus and Rhipicephalus [ Boophilus ] annulatus ; CFTs); therefore, deer are a concern for CFT control programs in southern Texas, US. Systemic (oral delivery of ivermectin) and topical (permethrin on pelage) treatment devices have been developed for white-tailed deer; however, the efficacy of these treatment options has not been determined for CFTs in southern Texas. Our objectives were to evaluate the effectiveness of CFT treatment strategies by 1) measuring exposure rates of deer to the acaricides permethrin and ivermectin, 2) determining the relationship between CFTs on deer and exposure to the acaricides, and 3) determining if photos from remote cameras at medicated bait sites can be used as a measure of acaricide treatment. We captured 327 deer at four sites in southern Texas. Deer visitation to medicated bait sites was monitored using remote cameras from March 2010 to February 2012. There was no relationship between the presence of permethrin and the probability of being infested with CFTs ( P ≥0.336). The probability of infestation with CFTs decreased as serum ivermectin levels increased for male ( n =18, P =0.098) and female ( n =33, P <0.001) deer. Our results indicate ivermectin may be more effective in treating CFTs than permethrin; thus it would be worthwhile to develop topical acaricides other than permethrin for treating white-tailed deer in southern Texas.
- Published
- 2020
- Full Text
- View/download PDF
15. Invasive Wild Pigs as Primary Nest Predators for Wild Turkeys.
- Author
-
Sanders HN, Hewitt DG, Perotto-Baldivieso HL, VerCauteren KC, and Snow NP
- Subjects
- Animals, Ecosystem, Female, Foxes physiology, Male, Nesting Behavior, Raccoons physiology, Seasons, Animals, Wild physiology, Introduced Species, Predatory Behavior, Swine physiology, Turkeys physiology
- Abstract
Depredation of wild turkey (Meleagris gallopavo) nests is a leading cause of reduced recruitment for the recovering and iconic game species. Invasive wild pigs (Sus scrofa) are known to depredate nests, and have been expanding throughout the distributed range of wild turkeys in North America. We sought to gain better insight on the magnitude of wild pigs depredating wild turkey nests. We constructed simulated wild turkey nests throughout the home ranges of 20 GPS-collared wild pigs to evaluate nest depredation relative to three periods within the nesting season (i.e., early, peak, and late) and two nest densities (moderate = 12.5-25 nests/km
2 , high = 25-50 nests/km2 ) in south-central Texas, USA during March-June 2016. Overall, the estimated probability of nest depredation by wild pigs was 0.3, equivalent to native species of nest predators in the study area (e.g., gray fox [Urocyon cinereoargenteus], raccoon [Procyon lotor], and coyote [Canis latrans]). Female wild pigs exhibited a constant rate of depredation regardless of nesting period or density of nests. However, male wild pigs increased their rate of depredation in areas with higher nest densities. Management efforts should remove wild pigs to reduce nest failure in wild turkey populations especially where recruitment is low.- Published
- 2020
- Full Text
- View/download PDF
16. Reproductive effort and success of males in scramble-competition polygyny: Evidence for trade-offs between foraging and mate search.
- Author
-
Foley AM, Hewitt DG, DeYoung RW, Schnupp MJ, Hellickson MW, and Lockwood MA
- Subjects
- Animals, Breeding, Female, Male, Marriage, Reproduction, Deer, Sexual Behavior, Animal
- Abstract
Patterns of male reproductive allocation provide insight into life-history characteristics. The trade-offs associated with resource and female group defence are well-defined. However, less is understood about trade-offs in species that practise scramble-competition polygyny, where successful strategies may favour competitive mate-searching rather than contest competition and fighting. White-tailed deer (Odocoileus virginianus) practise scramble-competition polygyny where solitary males search for and assess receptivity of females scattered across the landscape. Physically mature males are expected to do most of the breeding because of the high energetic costs of reproduction and high social status. However, young males may collectively sire one-third of offspring. To gain a better understanding of trade-offs associated with scramble-competition polygyny, we quantified metrics associated with reproductive effort and success. We quantified changes in body mass of harvested males, energetic costs of locomotion based on movements of GPS radiocollared males and timing of reproduction via temporal genetic parentage assignments. Young males (1.5 and 2.5 years old) sired offspring, but their mating success was mainly limited to peak rut, when most females were in oestrus. Furthermore, multiple paternity was common, indicating opportunistic reproduction. Reproductive effort, indexed by body mass loss, was highest in prime-age males (5.5-6.5 years old). Surprisingly, young and postprime males also exhibited significant body mass loss, indicative of investment in reproductive effort. Movement rates increased twofold to fourfold during rut as a function of mate search activities, but cost of locomotion would cause only about one-third of observed body mass loss. Because males are capital breeders, we infer most of body mass loss is due to reduced foraging. In scramble-competition polygyny, the repeated location of potential mates and assessment of their oestrous status appear to be important constituents of male mating strategies. Therefore, mating success may be influenced by time management and spatial memory, and not based solely on social dominance. Thus, reproductive effort should be greater for individuals capable of reducing time foraging. For those that cannot, opportunistic mating opportunities may arise when operative adult sex ratios are low. Our analyses reveal valuable insight into the trade-offs associated with scramble-competition polygyny., (© 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society.)
- Published
- 2018
- Full Text
- View/download PDF
17. Potential secondary poisoning risks to non-targets from a sodium nitrite toxic bait for invasive wild pigs.
- Author
-
Snow NP, Foster JA, VanNatta EH, Horak KE, Humphrys ST, Staples LD, Hewitt DG, and VerCauteren KC
- Subjects
- Animals, Female, Male, Sodium Nitrite metabolism, Vomiting chemically induced, Vomiting prevention & control, Animals, Wild, Pest Control instrumentation, Poisoning prevention & control, Sodium Nitrite toxicity, Sus scrofa
- Abstract
Background: An acute and orally delivered toxic bait containing micro-encapsulated sodium nitrite (MESN), is under development to provide a novel and humane technology to help curtail damage caused by invasive wild pigs (Sus scrofa). We evaluated potential secondary risks for non-target species by: testing whether four different types of micro-encapsulation coatings could reduce vomiting by invasive wild pigs, testing the levels of residual sodium nitrite (SN) in tissues of invasive wild pigs, testing the environmental persistence of SN in vomitus, and conducting a risk assessment for scavengers., Results: Micro-encapsulation coatings did not affect the frequency of vomiting. We identified no risk of secondary poisoning for non-target scavengers that consume muscle, eyes, and livers of invasive wild pig carcasses because residual SN from the toxic bait was not detected in those tissues. The risk of secondary poisoning from consuming vomitus appeared low because ∼90% of the SN was metabolized or broken down prior to vomiting, and continued to degrade after being exposed to the environment. Secondary poisoning could occur for common scavengers that consume approximately ≥15% of their daily dietary requirements of digestive tract tissues or undigested bait from carcasses of invasive wild pigs in a rapid, single-feeding event. The likelihood of this occurring in a natural setting is unknown. The digestive tracts of poisoned invasive wild pigs contained an average of ∼4.35 mg/g of residual SN., Conclusion: Data from this study suggest no risks of secondary poisoning for non-target species (including humans) that consume muscle, liver, or eyes of invasive wild pigs poisoned with a MESN toxic bait. More species-specific testing for scavengers that consume digestive tract tissues and undigested bait is needed to reduce uncertainty about these potential risks. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)
- Published
- 2018
- Full Text
- View/download PDF
18. Movement patterns of nilgai antelope in South Texas: Implications for cattle fever tick management.
- Author
-
Foley AM, Goolsby JA, Ortega-S A Jr, Ortega-S JA, Pérez de León A, Singh NK, Schwartz A, Ellis D, Hewitt DG, and Campbell TA
- Subjects
- Animals, Animals, Wild, Babesia microbiology, Babesiosis prevention & control, Cattle, Cattle Diseases prevention & control, Communicable Disease Control methods, Female, Geographic Information Systems, Humans, Male, Mexico, Movement, Rhipicephalus, Seasons, Texas, Antelopes parasitology, Babesiosis transmission, Cattle Diseases parasitology, Cattle Diseases transmission
- Abstract
Wildlife, both native and introduced, can harbor and spread diseases of importance to the livestock industry. Describing movement patterns of such wildlife is essential to formulate effective disease management strategies. Nilgai antelope (Boselaphus tragocamelus) are a free-ranging, introduced ungulate in southern Texas known to carry cattle fever ticks (CFT, Rhipicephalus (Boophilus) microplus, R. (B.) annulatus). CFT are the vector for the etiological agent of bovine babesiosis, a lethal disease causing high mortality in susceptible Bos taurus populations and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful. However, a permanent quarantine area is maintained between Texas and Mexico to check its entry from infested areas of neighboring Mexico states on wildlife and stray cattle. In recent years, there has been an increase in CFT infestations outside of the permanent quarantine area in Texas. Nilgai are of interest in understanding how CFT may be spread through the landscape. Thirty nilgai of both sexes were captured and fitted with satellite radio collars in South Texas to gain information about movement patterns, response to disturbances, and movement barriers. Median annual home range sizes were highly variable in males (4665ha, range=571-20,809) and females (1606ha, range=848-29,909). Female movement patterns appeared to be seasonal with peaks during June-August; these peaks appeared to be a function of break-ups in female social groups rather than environmental conditions. Nilgai, which reportedly are sensitive to disturbance, were more likely to relocate into new areas immediately after being captured versus four other types of helicopter activities. Nilgai did not cross 1.25m high cattle fences parallel to paved highways but did cross other fence types. Results indicate that females have a higher chance of spreading CFT through the landscape than males, but spread of CFT may be mitigated via maintenance of cattle fences running parallel with paved highways. Our results highlight the importance of documenting species-specific behavior in wildlife-livestock interfaces that can be used to develop effective disease management strategies in the United States and worldwide., (Published by Elsevier B.V.)
- Published
- 2017
- Full Text
- View/download PDF
19. Comparison of natural and artificial odor lures for nilgai ( Boselaphus tragocamelus ) and white-tailed deer ( Odocoileus virginianus ) in South Texas: Developing treatment for cattle fever tick eradication.
- Author
-
Goolsby JA, Singh NK, Ortega-S A Jr, Hewitt DG, Campbell TA, Wester D, and Pérez de León AA
- Abstract
Cattle fever ticks (CFT), vectors of bovine babesiosis and anaplasmosis, were eradicated from the United States by 1943, but are frequently reintroduced from neighboring border states of Mexico via stray cattle and wildlife hosts including white-tailed deer ( Odocoileus virginianus ) (WTD) and nilgai antelope ( Boselaphus tragocamelus ). Nilgai antelope are exotic bovids from India that are hosts of CFT, have large home ranges as compared to WTD, thus have the potential to spread CFT through the landscape. Currently, there are no methods to control CFT on nilgai. Odor lures were evaluated to determine if nilgai could be attracted to a central point for development of control methods. Four treatments, nilgai offal a natural odor lure was used as the positive control; and compared to three artificial odors; screw worm lure, volatile fatty acids, citronella oil. Studies were conducted on a free-ranging population of nilgai at the East Foundation's Santa Rosa Ranch (Kenedy Co., near Riviera, Texas, USA). Game cameras were used to document visitation to the lures. In the ten randomly placed transects, 110 nilgai and 104 WTD were photographed. Offal had significantly more visits by nilgai (71% of total visits) than screwworm (15%), VFA (11%), and citronella (4%). For WTD, there was no significant difference in visitation at the lure treatments.
- Published
- 2017
- Full Text
- View/download PDF
20. Neospora caninum in Axis Deer ( Axis axis ) and Fallow Deer ( Dama dama ) in Northern Mexico.
- Author
-
De La Torre JR, Bautista-Piña C, Alfonso Ortega-S J, Cantu-Covarruvias A, Genoveva Alvarez-Ojeda M, Romero-Salas D, Henke SE, Hilton CD, Hewitt DG, De Young RW, Campbell TA, and Bryant FC
- Subjects
- Animals, Enzyme-Linked Immunosorbent Assay, Mexico, Coccidiosis veterinary, Deer parasitology, Neospora isolation & purification
- Abstract
Serum samples from 18 axis deer ( Axis axis ) and 19 fallow deer ( Dama dama ) were analyzed with an enzyme-linked immunosorbent assay for Neospora caninum antibodies. Two axis (11%) and two fallow deer (11%) were positive for N. caninum antibodies.
- Published
- 2017
- Full Text
- View/download PDF
21. Modeled Impacts of Chronic Wasting Disease on White-Tailed Deer in a Semi-Arid Environment.
- Author
-
Foley AM, Hewitt DG, DeYoung CA, DeYoung RW, and Schnupp MJ
- Subjects
- Animals, Droughts, Female, Male, Surveys and Questionnaires, Deer, Environment, Models, Statistical, Wasting Disease, Chronic epidemiology
- Abstract
White-tailed deer are a culturally and economically important game species in North America, especially in South Texas. The recent discovery of chronic wasting disease (CWD) in captive deer facilities in Texas has increased concern about the potential emergence of CWD in free-ranging deer. The concern is exacerbated because much of the South Texas region is a semi-arid environment with variable rainfall, where precipitation is strongly correlated with fawn recruitment. Further, the marginally productive rangelands, in combination with erratic fawn recruitment, results in populations that are frequently density-independent, and thus sensitive to additive mortality. It is unknown how a deer population in semi-arid regions would respond to the presence of CWD. We used long-term empirical datasets from a lightly harvested (2% annual harvest) population in conjunction with 3 prevalence growth rates from CWD afflicted areas (0.26%, 0.83%, and 2.3% increases per year) via a multi-stage partially deterministic model to simulate a deer population for 25 years under four scenarios: 1) without CWD and without harvest, 2) with CWD and without harvest, 3) with CWD and male harvest only, and 4) with CWD and harvest of both sexes. The modeled populations without CWD and without harvest averaged a 1.43% annual increase over 25 years; incorporation of 2% annual harvest of both sexes resulted in a stable population. The model with slowest CWD prevalence rate growth (0.26% annually) without harvest resulted in stable populations but the addition of 1% harvest resulted in population declines. Further, the male age structure in CWD models became skewed to younger age classes. We incorporated fawn:doe ratios from three CWD afflicted areas in Wisconsin and Wyoming into the model with 0.26% annual increase in prevalence and populations did not begin to decline until ~10%, ~16%, and ~26% of deer were harvested annually. Deer populations in variable environments rely on high adult survivorship to buffer the low and erratic fawn recruitment rates. The increase in additive mortality rates for adults via CWD negatively impacted simulated population trends to the extent that hunter opportunity would be greatly reduced. Our results improve understanding of the potential influences of CWD on deer populations in semi-arid environments with implications for deer managers, disease ecologists, and policy makers., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2016
- Full Text
- View/download PDF
22. Bait Preference of Free-Ranging Feral Swine for Delivery of a Novel Toxicant.
- Author
-
Snow NP, Halseth JM, Lavelle MJ, Hanson TE, Blass CR, Foster JA, Humphrys ST, Staples LD, Hewitt DG, and VerCauteren KC
- Subjects
- Animals, Animals, Wild, Food Preferences, Introduced Species, Population Control, Texas, Poisons administration & dosage, Sodium Nitrite administration & dosage, Sus scrofa
- Abstract
Invasive feral swine (Sus scrofa) cause extensive damage to agricultural and wildlife resources throughout the United States. Development of sodium nitrite as a new, orally delivered toxicant is underway to provide an additional tool to curtail growth and expansion of feral swine populations. A micro-encapsulation coating around sodium nitrite is used to minimize detection by feral swine and maximize stability for the reactive molecule. To maximize uptake of this toxicant by feral swine, development a bait matrix is needed to 1) protect the micro-encapsulation coating so that sodium nitrite remains undetectable to feral swine, 2) achieve a high degree of acceptance by feral swine, and 3) be minimally appealing to non-target species. With these purposes, a field evaluation at 88 sites in south-central Texas was conducted using remote cameras to evaluate preferences by feral swine for several oil-based bait matrices including uncolored peanut paste, black-colored peanut paste, and peanut-based slurry mixed onto whole-kernel corn. These placebo baits were compared to a reference food, whole-kernel corn, known to be readily taken by feral swine (i.e., control). The amount of bait consumed by feral swine was also estimated using remote cameras and grid boards at 5 additional sites. On initial exposure, feral swine showed reduced visitations to the uncolored peanut paste and peanut slurry treatments. This reduced visitation subsided by the end of the treatment period, suggesting that feral swine needed time to accept these bait types. The black-colored peanut paste was visited equally to the control throughout the study, and enough of this matrix was consumed to deliver lethal doses of micro-encapsulated sodium nitrite to most feral swine during 1-2 feeding events. None of the treatment matrices reduced visitations by nontarget species, but feral swine dominated visitations for all matrices. It was concluded that black-colored peanut paste achieved satisfactory preference and consumption by feral swine, and no discernable preference by non-target species, compared to the other treatments.
- Published
- 2016
- Full Text
- View/download PDF
23. Tick-borne diseases in syntopic populations of fallow deer (Dama dama) and axis deer (Axis axis) in northern Mexico.
- Author
-
García-Vázquez Z, Ortega-S JA, Cantu-Covarruvias A, Mosqueda J, Hewitt DG, DeYoung RW, Campbell TA, and Bryant FC
- Subjects
- Animals, Babesiosis epidemiology, Female, Male, Mexico epidemiology, Species Specificity, Babesiosis parasitology, Deer
- Abstract
We harvested 21 fallow deer (Dama dama) and 17 axis deer (Axis axis) in northern Mexico. Two fallow deer were positive for Babesia bigemina and one for Babesia bovis. Amplicons had the expected 170 and 291 base pairs and were identical to B. bigemina (S45366) and B. bovis (M38218), respectively.
- Published
- 2015
- Full Text
- View/download PDF
24. Nilgai antelope in northern Mexico as a possible carrier for cattle fever ticks and Babesia bovis and Babesia bigemina.
- Author
-
Cárdenas-Canales EM, Ortega-Santos JA, Campbell TA, García-Vázquez Z, Cantú-Covarrubias A, Figueroa-Millán JV, DeYoung RW, Hewitt DG, and Bryant FC
- Subjects
- Animals, Babesia bovis isolation & purification, Babesiosis epidemiology, Babesiosis transmission, Carrier State parasitology, Carrier State veterinary, Cattle, Disease Reservoirs veterinary, Female, Male, Mexico epidemiology, Tick Infestations veterinary, Antelopes parasitology, Babesia isolation & purification, Babesiosis veterinary, Ticks parasitology
- Abstract
Of 20 blood samples from nilgais from México, five were polymerase chain reaction-positive for Babesia bigemina and one for Babesia bovis. Positive samples had the expected 170 (B. bigemina) and 291 (B. bovis) base pairs and were identical to Gen-Bank B. bigemina accession S45366 and B. bovis M38218.
- Published
- 2011
- Full Text
- View/download PDF
25. One Health approach to identify research needs in bovine and human babesioses: workshop report.
- Author
-
Pérez de León AA, Strickman DA, Knowles DP, Fish D, Thacker E, de la Fuente J, Krause PJ, Wikel SK, Miller RS, Wagner GG, Almazán C, Hillman R, Messenger MT, Ugstad PO, Duhaime RA, Teel PD, Ortega-Santos A, Hewitt DG, Bowers EJ, Bent SJ, Cochran MH, McElwain TF, Scoles GA, Suarez CE, Davey R, Howell Freeman JM, Lohmeyer K, Li AY, Guerrero FD, Kammlah DM, Phillips P, and Pound JM
- Abstract
Background: Babesia are emerging health threats to humans and animals in the United States. A collaborative effort of multiple disciplines to attain optimal health for people, animals and our environment, otherwise known as the One Health concept, was taken during a research workshop held in April 2009 to identify gaps in scientific knowledge regarding babesioses. The impetus for this analysis was the increased risk for outbreaks of bovine babesiosis, also known as Texas cattle fever, associated with the re-infestation of the U.S. by cattle fever ticks., Results: The involvement of wildlife in the ecology of cattle fever ticks jeopardizes the ability of state and federal agencies to keep the national herd free of Texas cattle fever. Similarly, there has been a progressive increase in the number of cases of human babesiosis over the past 25 years due to an increase in the white-tailed deer population. Human babesiosis due to cattle-associated Babesia divergens and Babesia divergens-like organisms have begun to appear in residents of the United States. Research needs for human and bovine babesioses were identified and are presented herein., Conclusions: The translation of this research is expected to provide veterinary and public health systems with the tools to mitigate the impact of bovine and human babesioses. However, economic, political, and social commitments are urgently required, including increased national funding for animal and human Babesia research, to prevent the re-establishment of cattle fever ticks and the increasing problem of human babesiosis in the United States.
- Published
- 2010
- Full Text
- View/download PDF
26. Models from past mold the future in evidence-based health care design.
- Author
-
Hewitt DG
- Subjects
- Catholicism, Hospitals, Religious, Humans, Evidence-Based Medicine, Facility Design and Construction
- Published
- 2010
27. Feral swine contact with domestic swine: a serologic survey and assessment of potential for disease transmission.
- Author
-
Wyckoff AC, Henke SE, Campbell TA, Hewitt DG, and VerCauteren KC
- Subjects
- Animal Identification Systems, Animals, Animals, Domestic, Animals, Wild, Brucellosis blood, Brucellosis epidemiology, Brucellosis transmission, Brucellosis veterinary, Female, Geographic Information Systems, Male, Porcine Reproductive and Respiratory Syndrome blood, Porcine Reproductive and Respiratory Syndrome epidemiology, Porcine Reproductive and Respiratory Syndrome transmission, Pseudorabies blood, Pseudorabies epidemiology, Pseudorabies transmission, Swine, Swine Diseases blood, Swine Diseases epidemiology, Texas epidemiology, Antibodies, Bacterial blood, Antibodies, Viral blood, Disease Transmission, Infectious veterinary, Sus scrofa, Swine Diseases transmission
- Abstract
Feral swine (Sus scrofa) are present in 38 of the 50 United States, and their populations continue to expand. Domestic swine are widely regarded as vulnerable to diseases harbored by feral swine. Our objectives were to determine antibody prevalence for selected pathogens in Texas feral swine populations and identify contact events between feral and domestic swine. Overall prevalence of antibodies against brucellosis and pseudorabies virus was 11% and 30%, respectively. Antibodies to porcine reproductive and respiratory disease virus were detected in 3% of feral swine from southern Texas. All samples tested negative for antibodies to classical swine fever virus. To determine the frequency of contact events between feral swine and domestic swine in neighboring facilities, we analyzed movement data from 37 adult feral swine that were trapped < or =10 km from domestic swine facilities and equipped with geographic positioning system collars. Seven of the 37 feral swine had contact (relocated within 100 m) with domestic swine. We found that contact between feral swine and domestic swine occurred predominantly at night. Additionally, we analyzed 60 consecutive days of experimental track plots around pens that contained domestic swine and empty control pens, and found greater visitation by feral swine to the domestic swine pens. Our data demonstrate that feral swine have direct contact with domestic swine, which presents opportunity for disease transmission.
- Published
- 2009
- Full Text
- View/download PDF
28. The thin line between malpractice and benefit determination.
- Author
-
Rovner JA and Hewitt DG
- Subjects
- Decision Making, Employee Retirement Income Security Act legislation & jurisprudence, Humans, Male, New York, Refusal to Treat legislation & jurisprudence, Therapies, Investigational economics, United States, Eligibility Determination legislation & jurisprudence, Health Maintenance Organizations legislation & jurisprudence, Insurance Claim Review legislation & jurisprudence, Malpractice legislation & jurisprudence
- Published
- 2003
29. Effect of metabolic acidosis on white-tailed deer antler development.
- Author
-
Campbell TA and Hewitt DG
- Subjects
- Acidosis physiopathology, Animals, Body Weight, Calcium, Dietary metabolism, Energy Intake, Glucuronic Acid urine, Male, Phosphorus, Dietary metabolism, Random Allocation, Acidosis veterinary, Antlers growth & development, Deer growth & development, Diet
- Abstract
Metabolic acidosis can result when herbivores consume browse diets high in plant secondary compounds. One mechanism for buffering excess acid is the mobilization of calcium and other alkaline salts from the skeletal system. White-tailed deer (Odocoileus virginianus) and other cervids consuming browse during antler formation may use minerals essential for antler development as buffers, resulting in altered antler characteristics. Our research objectives were to examine the effects of metabolic acidosis on mineral metabolism, acid-base homeostasis, and antler development in white-tailed deer. Fifteen male white-tailed deer were assigned to one of three diets: 2% NH(4)Cl, 3% commercial tannic acid, or a basal ration without additive. Two feeding trials were completed on each deer to determine nutrient use. Urine pH and the percentage of urinary nitrogen excreted as NH+4 varied by diet. No significant diet or trial effects occurred for nitrogen, calcium, phosphorus, magnesium, or sodium use. Urinary calcium excretion varied between diets. No dietary differences were observed for antler characteristics. The NH(4)Cl diet induced metabolic acidosis but did not alter antler development in white-tailed deer. Skeletal mineral reserves and mineral intake appeared sufficient to buffer excess acids and support antler development.
- Published
- 2000
- Full Text
- View/download PDF
30. Cholinesterase activity in white-winged doves exposed to methyl parathion.
- Author
-
Small MF, Pruett CL, Hewitt DG, Hellgren EC, Perrigo GH, and Waggerman GL
- Subjects
- Administration, Oral, Animals, Brain drug effects, Cholinesterase Inhibitors administration & dosage, Cholinesterases blood, Dose-Response Relationship, Drug, Drinking, Insecticides administration & dosage, Methyl Parathion administration & dosage, Brain enzymology, Cholinesterase Inhibitors toxicity, Cholinesterases metabolism, Columbidae metabolism, Insecticides toxicity, Methyl Parathion toxicity
- Abstract
Captive white-winged doves (Zenaida asiatica) were exposed to various levels of methyl parathion (MP) in drinking water to determine effects on brain and blood cholinesterase (ChE) activity. We conducted two experiments to test the influence of MP dose (the amount of MP actually ingested), MP concentration (the amount of MP per unit water), and exposure duration (number of days exposed to a constant MP concentration) on ChE activity. Plasma ChE activity was not useful in predicting brain ChE activity. Methyl parathion concentration had a greater influence on plasma and brain ChE activity levels than dose or time of exposure. These results contribute to the evaluation of irrigation water as a route of exposure of wildlife to pesticides.
- Published
- 1998
- Full Text
- View/download PDF
31. Effect of tannins on galliform cecal partitioning.
- Author
-
Hewitt DG, Lafon NW, and Kirkpatrick RL
- Subjects
- Animals, Body Weight drug effects, Chromium analysis, Chromium pharmacokinetics, Cobalt analysis, Cobalt pharmacokinetics, Diet, Feces chemistry, Gastrointestinal Transit, Male, Tannins administration & dosage, Tannins pharmacology, Birds physiology, Cecum physiology, Tannins metabolism
- Abstract
Winter diets of ruffed grouse (Bonasa umbellus) and other galliformes are high in tannins. We fed quebracho, a condensed tannin, to ruffed grouse and found no effect on dry matter intake or body mass at levels up to 6% of the diet. However, a high-fiber diet with 8% quebracho resulted in reduced dry matter intake and body mass loss. Grouse could not tolerate a diet with 8% tannic acid, a hydrolyzable tannin, which caused a large reduction in dry matter intake and body mass. Northern bobwhite (Colinus virginianus) and ruffed grouse responded to dietary quebracho tannin by increasing the proportion of digesta that was excreted from the ceca. In the northern bobwhite, 59%-76% of the tannin recovered from the feces was in cecal feces. There was no difference in average passage rates of liquid and fiber digesta, although variation was high in tannin-fed birds. The role of the ceca in handling tannin requires further investigation.
- Published
- 1997
- Full Text
- View/download PDF
32. The chemical origin of free radicals in coffee and other beverages.
- Author
-
Gonis J, Hewitt DG, Troup G, Hutton DR, and Hunter CR
- Subjects
- Electron Spin Resonance Spectroscopy, Free Radicals chemistry, Beverages, Coffee chemistry
- Abstract
Sugars or carbohydrates are identified as the source of free radicals in coffees, ersatz coffees, a number of other food flavouring and colouring agents formed by processes involving heating, and in beers and stouts. The radicals are not derived from phenolic constituents, in contrast to those in wine, and are unlikely to be due solely to the occurrence of Maillard reactions.
- Published
- 1995
- Full Text
- View/download PDF
33. Free radicals in red wine, but not in white?
- Author
-
Troup GJ, Hutton DR, Hewitt DG, and Hunter CR
- Subjects
- Electron Spin Resonance Spectroscopy methods, Fermentation, Free Radicals analysis, Glycosides analysis, Manganese analysis, Phenols analysis, Trees, Wine analysis
- Abstract
By using Electron Spin Resonance (ESR) spectroscopy, we have detected free radicals in red wine, whether fermented on oak or not, and in white wine only when it has been fermented on oak. These radicals would appear to be associated with the phenolics, because the ESR signal from the residue of red wine treated with polyvinyl polypyrrolidone is reduced by approximately 80%. Any inhibition of lipid oxidation by red wine phenolics in vitro will take place in the presence of these radicals, which have a linewidth of 2.0 +/- 0.1 gauss and a g-value of 2.0038 +/- 0.0001.
- Published
- 1994
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.