Water Quality for Cattle: Metalloid and Metal Contamination of Water.

Water is the most important nutrient for rangeland livestock. However, competition with municipalities, industry, and other water users often results in grazing livestock being forced to use water supplies that are less than perfect. Surface water in western rangleands are often contaminated by mineral extraction, irrigation runoff and other human activities. Mineral contaminants in drinking water are additive with similar contaminants in feedstuffs. The goal of this article is to provide producers and veterinarians with the basic background to make informed decisions about whether a given water supply is "safe" for livestock.

Selenosis in Ruminants.

Selenium (Se) is a metalloid that exists as a red amorphous powder, reddish crystal, silver-gray crystal, or brown-black solid. Its potency as a nutrient and a toxicant is such that few people have seen the pure element. It is easy to lose sight of the narrow margin between too little and too much. The most common cause of selenosis is accidental or intentional overuse of supplements. Many target organs and effects of Se toxicity are similar to those of Se deficiency, so laboratory confirmation is necessary. Prevention consists of minimizing exposure to seleniferous feedstuffs and optimizing dietary factors that might aggravate selenosis.

Water Quality for Grazing Livestock I.

Water is the most important nutrient for rangeland livestock. However, competition with municipalities, industry, and other water users often results in grazing livestock being forced to use water supplies that are less than perfect. Surface water in western rangleands are often contaminated by mineral extraction, irrigation runoff and other human activities. Mineral contaminants in drinking water are additive with similar contaminants in feedstuffs. The goal of this and the subsequent article is to provide producers and veterinarians with the basic background to make informed decisions about whether a given water supply is "safe" for livestock.

Huntingtons Disease Mice Infected with Toxoplasma gondii Demonstrate Early Kynurenine Pathway Activation, Altered CD8+ T-Cell Responses, and Premature Mortality.

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a polyglutamine-repeat expansion in the huntingtin protein. Activation of the kynurenine pathway of tryptophan degradation is implicated in the pathogenesis of HD. Indoleamine-2,3-dioxygenase (IDO) catalyzes the oxidation of tryptophan to kynurenine, the first step in this pathway. The prevalent, neuroinvasive protozoal pathogen Toxoplasma gondii (T. gondii) results in clinically silent life-long infection in immune-competent individuals. T. gondii infection results in activation of IDO which provides some protection against the parasite by depleting tryptophan which the parasite cannot synthesize. The kynurenine pathway may therefore represent a point of synergism between HD and T. gondii infection. We show here that IDO activity is elevated at least four-fold in frontal cortex and striata of non-infected N171-82Q HD mice at 14-weeks corresponding to early-advanced HD. T. gondii infection at 5 weeks resulted in elevation of cortical IDO activity in HD mice. HD-infected mice died significantly earlier than wild-type infected and HD control mice. Prior to death, infected HD mice demonstrated decreased CD8+ T-lymphocyte proliferation in brain and spleen compared to wild-type infected mice. We demonstrate for the first time that HD mice have an altered response to an infectious agent that is characterized by premature mortality, altered immune responses and early activation of IDO. Findings are relevant to understanding how T. gondii infection may interact with pathways mediating neurodegeneration in HD.

Secondary pentobarbital poisoning in two dogs: a cautionary tale.

Two dogs, a 13-year-old spayed female and a 7-year-old neutered male, were diagnosed with pentobarbital poisoning. Follow-up investigation determined that the source of pentobarbital was the carcass of a horse that had been euthanized more than 2 years previously and that was also apparently responsible for the death of a least 1, and possibly 2, other dogs. The fact that the horse carcass remained lethally toxic more than 2 years after it was euthanized reemphasizes the necessity of proper disposal of euthanized animals.

Experimental reproduction of tumbleweed shield lichen (Xanthoparmelia chlorochroa) poisoning in a domestic sheep model.

Xanthoparmelia chlorochroa, commonly called tumbleweed lichen, is found throughout the Rocky Mountain region. This particular species of lichen was incriminated in the poisoning of cattle and sheep in Wyoming during the 1930s. More than 70 years elapsed before another case was reported. There is virtually no information in the veterinary literature regarding toxicity of this lichen. This report describes X. chlorochroa poisoning in domestic sheep fed lichen collected from different locales and at different times of the year. Affected animals voided red urine and displayed incoordination. A transient spike in serum creatine kinase activity occurred in all ewes during the course of the feeding trial. Histologically, necrosis of a few individual appendicular skeletal myocytes was observed in 1 ewe, but grossly discernible myonecrosis was absent. The severity of clinical signs varied depending on the location and/or time of year the lichen was collected, indicating that toxicity of the lichen may be influenced by environmental conditions. Results demonstrate that domestic sheep are a useful model for further investigation of X. chlorochroa intoxication. The current study should act as a starting point for elucidating the pathogenesis of X. chlorochroa poisoning and aid in the development of a diagnostic assay to confirm lichen poisoning.

Liver metal concentrations in Greater Sage-grouse (Centrocercus urophasianus).

Greater Sage-grouse (Centrocercus urophasianus) are a species of concern due to shrinking populations associated with habitat fragmentation and loss. Baseline health parameters for this species are limited or lacking, especially with regard to tissue metal concentrations. To obtain a range of tissue metal concentrations, livers were collected from 71 Greater Sage-grouse from Wyoming and Montana. Mean +/- SE metal concentrations (mg/kg wet weight) in liver were determined for vanadium (V) (0.12 +/- 0.01), chromium (Cr) (0.50 +/- 0.02), manganese (Mn) (2.68 +/- 0.11), iron (Fe) (1,019 +/- 103), nickel (Ni) (0.40 +/- 0.04), cobalt (Co) (0.08 +/- 0.02), copper (Cu) (6.43 +/- 0.40), mercury (Hg) (0.30 +/- 0.09), selenium (Se) (1.45 +/- 0.64), zinc (Zn) (59.2 +/- 4.70), molybdenum (Mo) (0.93 +/- 0.07), cadmium (Cd) (1.44 +/- 0.14), barium (Ba) (0.20 +/- 0.03), and lead (Pb) (0.17 +/- 0.03). In addition to providing baseline data, metal concentrations were compared between sex, age (juvenile/adult), and West Nile virus (WNv) groups (positive/negative). Adult birds had higher concentrations of Ni and Cd compared to juveniles. In addition, Zn and Cu concentrations were significantly elevated in WNv-positive birds.

Paresis and death in elk (Cervus elaphus) due to lichen intoxication in Wyoming.

During February-April 2004, an estimated 400-500 free-ranging elk (Cervus elaphus) developed paresis, became recumbent, and died or were euthanized in the Red Rim Wildlife Habitat Management Area (RRWHMA), Wyoming, USA. Elk were found in sternal recumbency, alert and responsive, but unable to rise. Their condition progressed to lateral recumbency followed by dehydration, obtundation, and death. Gross lesions were limited to degenerative myopathy, with pallor and streaking in skeletal muscles. Microscopically, affected muscles had degenerative lesions of varying duration, severity, and distribution, some with early mineralization and attempts at regeneration. Diagnostic testing ruled out common infectious, inflammatory, toxic, and traumatic causes. Tumbleweed shield lichen (Xanthoparmelia chlorochroa) was found in the area and in the rumen of several elk. This lichen was collected and fed to three captive elk. Two of these elk exhibited signs of ataxia, which rapidly progressed to weakness and recumbency after 7 and 10 days on this diet, respectively, and a degenerative myopathy, consistent with lesions observed in the elk affected at RRWHMA, was observed. All remaining elk migrated from the RRWHMA during the spring and no subsequent losses have been documented.

Modest copper supplementation blocks molybdenosis in cattle.

It is widely accepted that ratios of dietary copper (Cu) to molybdenum (Mo) lower than 10:1 may produce molybdenosis in cattle, especially if sulfur concentrations are more than 3,000 ppm. Some authorities suggest that dietary Mo concentrations greater than 10 ppm are hazardous to cattle regardless of Cu concentration, but anecdotal reports suggest that this may not be the case. The original purpose of the experiment described in this report was to investigate whether supranutritional supplemental Cu could protect cattle against relatively high dietary Mo. Pregnant cows were grazed on 1 of 3 pastures: 1 with only background Mo, 1 with an average of 13 ppm Mo, and 1 that averaged 230 ppm Mo. Half the cows on the Mo pastures were supplemented with 17 ppm dietary Cu, the other half with the dietary supplement plus Cu boluses. Molybdenum effects were anticipated in the groups supplemented with 17 ppm Cu; however, despite increased tissue concentrations of Mo, only the 230 ppm Mo/17 ppm Cu group exhibited any effects. Moderate Cu supplementation permitted cows to graze a site heavily contaminated with Mo with no adverse effects on general health or reproduction.

The bioactivity-guided isolation and structural identification of toxic cucurbitacin steroidal glucosides from stemodia kingii.

A histologically validated murine model for the ovine intoxication by Stemodia kingii was used as a bioassay to guide the isolation of several groups of toxins from Stemodia kingiL Two of the toxins from one group were purified sufficiently to allow structural analysis and a determination of their median lethal doses (LD50) for oral administration to mice. A combination of acid hydrolysis, elemental analysis, HPLC-MS, 1D-NMR (1H, 13C) and 2D-NMR (1H-1H COSY, 13C-1H HSQC and HMBC, and gNOESY) was used to define stemodiosides B3 and B4 as cucurbitacin steroidal glucosides. Thus stemodioside B3 is (24Z)-3 alpha-(beta-glucopyranosyloxy)-2 beta,20,27-trihydroxy- 19-(10 -9 beta)-abeo-10alpha-lanost-5,24-diene- 11-one and stemodioside B4 is (23E)-3 alpha-(beta-glucopyranosyloxy)-20,20,22,27-tetrahydroxy- 19-( 10-9 beta)-abeo- 10 alpha-lanost-5,23-diene- 11-one. The approximate oral LD50s for stemodiosides B3 and B4 in mice were estimated to be 99 and 42 mg/kg body weight, respectively.

Toxic effects of a single parenteral dose of tunicamycin in late stage pregnancy in rats.

Tunicamycin (TM) was given as a single parenteral dose at 3 levels to female rats at gestation day 15 (GD 15) and also to non-pregnant rats. At 16 h post-dosing all pregnant rats had moderate to extensive vaginal bleeding and 1/4 at each of the 2 higher doses died. The other severely affected rats, euthanized after 26-28 h, had free blood in the uterus and large decreases in red cell count (RCC), hemoglobin (Hb) and packed cell volume (PCV). The amnion of the fetuses was very easily detached from the maternal placenta by gentle manipulation. Histologically, hemorrhage, venous thrombosis and ischemic necrosis, particularly in the maternal placenta, were consistent with the gross appearance. There was no hemorrhage in any control pregnant rats. In the remaining TM-treated pregnant rats, euthanized at GD 17, there were lesser dose-related decreases in RCC, Hb and PCV, but there was no evidence of bleeding or changes in red blood cell parameters in non-pregnant rats. There was a dose-related decrease in cholesterol and GlcNAc-1-P transferase (GPT) activity and a treatment-related decrease in serum proteins in all rats. Maternal toxicity was demonstrated in pregnant rats at TM doses < 10% of a TM lethal dose in non-pregnant rats.