Historical Changes in Stocking Densities on Texas Rangelands

Stocking density, both current and past, is a major determinant of the nature and condition of rangelands. Despite this fact, there have been few detailed examinations of historical trends in stocking density. We used data from the U.S. Census of Agriculture to track the density of domestic livestock from the early 1900s to the present, for six rangeland regions in the State of Texas: (1) the Edwards Plateau; (2) the Trans-Pecos; (3) the Lampasas Cut Plain; (4) the South Texas Plains; (5) the Rolling Plains; and (6) the High Plains. We find that stocking densities have declined across the state—ranging from a decline of about 40% in some regions to as much as 75% in the Trans-Pecos and Edwards Plateau regions. The period of sharpest decline, which began in the middle of the last century, reflects important, but not fully understood, socioeconomic changes. These most likely include changing land ownership, fragmentation of land holdings, and increasing emphasis on wildlife conservation. Other factors potentially contributing to the destocking of Texas rangelands include woody plant encroachment and a rise in predation. We argue that the dramatic reduction in stocking densities documented here has profound socioeconomic, ecological, and hydrological implications that need to be better understood.     

Serological assays to discriminate rabbit haemorrhagic disease virus from Australian non-pathogenic rabbit calicivirus

Serological cross reactivity between the virulent rabbit haemorrhagic disease virus (RHDV) and the closely related but non-pathogenic rabbit calicivirus (RCV) makes it difficult to study the epidemiology of each virus and the interaction between them when both viruses co-circulate in wild rabbit populations. ELISA methods for the diagnosis of RHDV infection are well characterized, but no specific serological tests for RCV have been developed. Following the characterization of Australian non-pathogenic RCV-A1 strains, we used virus-like-particles (VLPs) and anti-RCV-A1 specific antibodies to establish a set of isotype ELISAs for detection of IgG, IgA and IgM in rabbit sera and secretory mucosal IgA in rectal swabs, and two competition ELISAs. These assays were used to discriminate between anti-RCV-A1 and anti-RHDV antibodies in rabbits. The isotype ELISAs were highly sensitive for detection of anti-RCV-A1 antibodies, but varying levels of cross reactivity from anti-RHDV antibodies occurred in the isotype ELISAs and one competition ELISA. However, the second competition ELISA specifically detected antibodies to RCV-A1 and showed no cross reactivity to anti-RHDV sera. These ELISAs provide important tools to monitor RCV-A1 infection when it occurs alone, and to discriminate between RHDV and RCV-A1 infection when they occur in the same rabbit population. When used in parallel with RHDV serology, they could be used to monitor the dynamics of these two closely related but pathogenically distinct viruses in wild and domestic rabbit populations.     

Dynamic controlled atmosphere (DCA): Does fluorescence reflect physiology in storage?

A link between the minimum fluorescence (F_o) and a metabolic shift from predominantly aerobic to fermentative metabolism [i.e. the lower oxygen limit (LOL)] is the foundation of dynamic controlled atmosphere (DCA). Current DCA technology uses pulse frequency modulated (PFM) sensors and employs a range of light intensities and extrapolation to measure F_α, an approximation of F_o. Like fruit mass, colour, sugar or acid levels, the LOL is inherently variable, even between apples (Malus domestica) (for example) from a given cultivar and tree or between the sun-exposed and shaded regions of a single fruit. The physiological link between metabolism and fluorescence has not been extensively studied. However, recent work suggests the low-O₂-induced rise in F_α results from a shut down of mitochondrial function and a buildup of reductant that leads to an over-reduction of the plastoquinone (PQ) pool and a decrease in photochemical quenching. Hypoxic conditions above the LOL can decrease F_α slightly in some species, possibly as a result of zeaxanthin formation and increased non-photochemical quenching. Low-intensity light differentially affects F_α depending on the O₂ level: light increases F_α when O₂ levels are above the LOL due to light-induced reduction of the oxidized PQ pool, but decreases the elevated F_α signal below the LOL as a result of a PSI-driven oxidation of the over-reduced PQ pool. Temperature has a negative, primarily non-physiological correlation with the F_α baseline which seems unrelated to the PQ pool redox state. Understanding how O₂ and other factors affect F_α may improve the utility and commercial application of DCA.     

Comparison of Sewage and Coal-Mine Wastes on Stream Macroinvertebrates Within an Otherwise Clean Upland Catchment, Southeastern Australia

Macroinvertebrates have been widely used in freshwater ecosystems as surrogates to assess the impacts of waste discharges and water pollution. However, often interpretations have been made on the impact of one pollutant in the presence of others that may provide an unidentified additive effective or otherwise confound the results. There have been few opportunities to study the impact of pollutants without such potentially confounding effects. We studied macroinvertebrates using a replicated kick sampling technique and identified to the family level to assess and compare the effects of zinc-rich coal-mine waste and organic pollution from treated sewage on an otherwise clean upland stream network within a world heritage area. We used multivariate analysis of macroinvertebrate assemblages from polluted and clean sites to measure and compare the effect of each waste impact to community structure. We also calculated three widely used biotic indices (Ephemeroptera, Plecoptera and Trichoptera (EPT) family richness, family richness, and abundance) and found that the EPT index was the only one to respond to both pollution types. Macroinvertebrate abundance was an important attribute of the study, with each source of pollution having a contrasting effect on total abundance. It also helped us to measure the relative response of families to each pollutant. There was an initial significant modification of macroinvertebrate assemblages below the outflow of each of the pollutants, followed by different degrees of recovery downstream.     

Arthroscopic diagnosis and treatment of intra-articular insertional injuries of the suspensory ligament branches in 18 horses

REASONS FOR PERFORMING STUDY: Clinical association between the branches of insertion of the suspensory ligament (SL) and metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints has been reported. However, there has been no assessment of the lengths of the SL branches which are subsynovial with respect to the joints or reports of involvement of the MCP/MTP joints in injuries of the SL branches. OBJECTIVES: To establish proportions of SL branches subsynovial with respect to the MCP/MTP joints and report clinical and arthroscopic findings in horses with desmitis of SL branches identified as having an articular component to the lesion. HYPOTHESIS: Arthroscopic surgery enables identification and potential treatment of intra-articular injuries of SL branches. METHODS: Twelve forelimbs and 13 hindlimbs were dissected and the total and subsynovial lengths of the SL branches recorded. Case records of horses with intra-articular injuries of the SL branches were reviewed and 18 animals identified. Diagnostic information and arthroscopic findings were recorded and results of treatment determined by telephone follow-up. RESULTS: Of SL branches, 28.45% in the forelimb and 29.56% in the hindlimb were subsynovial to the MCP and MTP joints. All animals with intra-articular lesions of the SL branch were lame and had distension of the affected MCP/MTP joint. In 16 horses (17/22 branches), there was palpable thickening of the affected SL branch. Disrupted infrastructure was evident ultrasonographically in 15/17 branches and involvement of the dorsal articular surface of the ligament was predicted in 12/17 branches. Following arthroscopic intervention, 13 horses returned to work at a level equal to or greater than that achieved prior to injury and 2 returned to work at a lower level. Three horses incurred separate injuries and were retired or subjected to euthanasia. CONCLUSIONS: Articular involvement should be considered in animals with injuries of an SL branch and concurrent distension of the MCP/MTP joint. Arthroscopy is necessary to identify such lesions confidently and to direct case management. POTENTIAL RELEVANCE: Arthroscopy of the MCP/MTP joints can make a positive contribution to the assessment and management of some SL branch injuries.     

Diagnosis and treatment of a feline oral mast cell tumor

A cat was diagnosed with an oral mast cell tumor following incisional biopsy. The location of the tumor, possible metastasis, financial restraint and patient disposition severely limited therapeutic options. The patient was treated with six doses of 1-(2-chloroethyl)3-cyclohexyl-1-nitrosurea (CCNU) and methylprednisolone acetate. Complete remission was obtained after the third dosing regimen. This is the first documented case of feline oral mast cell tumor and one of a small group of cats with various cancers to be responsive to CCNU treatment.     

Sampling the antibiotic resistome

Microbial resistance to antibiotics currently spans all known classes of natural and synthetic compounds. It has not only hindered our treatment of infections but also dramatically reshaped drug discovery, yet its origins have not been systematically studied. Soil-dwelling bacteria produce and encounter a myriad of antibiotics, evolving corresponding sensing and evading strategies. They are a reservoir of resistance determinants that can be mobilized into the microbial community. Study of this reservoir could provide an early warning system for future clinically relevant antibiotic resistance mechanisms.     

Babesia bovis--analysis and vaccination trial with the cryoprecipitable immune complex

Plasma samples from cattle recovering from acute Babesia bovis infection contain cryoprecipitable immune complexes (IC). Production of bovine and rabbit antisera to IC and subsequent serological assays indicated IC contained antigens of both babesial and erythrocytic origin. Vaccination of naive cattle with IC produced low titred antibody to B. bovis but the vaccinates did not survive challenge with a heterologous strain of B. bovis.