Investigation of an outbreak of Aleutian disease on a commercial mink ranch.

OBJECTIVE: To determine the modes of transmission of Aleutian mink disease in a natural outbreak. ANIMALS: 5,580 black and 9,087 brown mink from a ranch with an outbreak of Aleutian mink disease. PROCEDURE: Each mink had serum tested by counter-electrophoresis for Aleutian disease antibody. If a mink was seropositive for Aleutian disease virus by counter-electrophoresis, it was considered to be infected. Correlation of prevalence of the disease in kits and parents was determined. Spatial arrangement of infected and un-infected mink also was studied. RESULTS: Infected black dams were more likely to produce infected kits than were uninfected dams. In contrast, infected black sires were less likely to produce infected kits than were uninfected sires. In brown mink, in which prevalence of Aleutian disease was lower, transmission from infected dams and sires to kits was apparent. Infected black mink appeared to be more efficient in transmitting the disease horizontally than were infected brown mink. Although the spatial arrangement of infected mink indicated that mechanical transmission of the disease may be the most efficient mode of horizontal transmission, airborne transmission also occurred. CONCLUSIONS AND CLINICAL RELEVANCE: Infected sires with nonprogressive Aleutian disease may confer protection to their kits in the face of a severe outbreak. Brown mink may be less able to transmit the virus horizontally than are black mink. Airborne transmission is substantial, but may not be as efficient as mechanical transmission.

Comparison of calf housing types and tympanic temperature rhythms in Holstein calves.

During fall, 30 Holstein calves were randomly assigned to three housing treatments from birth to weaning: conventional wooden hutches, enclosed molded polyethylene domes, and thermomolded opaque polymer hutches with ridge-top ventilation systems. The wooden and polymer hutches had outdoor pens. Fifteen calves, 5 in each housing type, were fitted with portable data loggers to record ambient (calf microclimate) and tympanic temperatures. Additional data collected included weekly girth, BW, and feed intake; blood samples were collected within 24 h of birth and at weaning (8 wk); and behavioral observations were made at 1, 4, and 7 wk of age. Polyethylene domes had the warmest microclimate, followed by wooden and polymer hutches. Feed intake, growth measurements, blood physiology, and behavior were unaffected by housing type. Diurnal tympanic temperature rhythms of neonatal dairy calves in this study were monophasic: maximums were at 1200 to 1700 h, and minimums were at 0600 to 0900 h. Computed fractal dimensions of tympanic temperature by week indicated a gradual diminishing of stress as the calves became older and acclimated to their environment. This objective characterization provides a basis for further evaluation of physiological stress and a means of improving environmental management.

Enumeration of total bacteria in raw and pasteurized milk by reflectance colorimetry: collaborative study.

Seven out of 9 laboratories completed a collaborative study comparing a reflectance colorimetric (RC) bioactivity monitor (Omnispec 4000) method to the standard plate count (SPC) method for estimation of total bacteria in raw and homogenized pasteurized milk. Each laboratory analyzed 12 different samples by the SPC method and 24 samples (12 blind duplicates) by the RC method. For the RC method RSDr was 1.7%, and RSDR was 4.5%. RSDR for the SPC method was 20.8%. The method was adopted first action by AOAC INTERNATIONAL.

Toxicity of extracts of tall larkspur (Delphinium barbeyi) in mice, hamsters, rats and sheep.

Larkspur consumption is a major source of cattle losses on mountain and high plains rangelands of western North America. Our objective was to find a suitable laboratory animal model for measuring larkspur toxicity for subsequent use as an estimator of toxicity to cattle. The LD50 for subcutaneous injection and for oral gavage of extract from Delphinium barbeyi, a highly toxic and troublesome rangeland tall larkspur, was compared for mice, hamsters, rats and sheep. Similarity of primary clinical signs of poisoning and lack of significant difference in slope of the dose-response curves implied that the overall effect of the larkspur alkaloids was the same for all rodent species tested. Sheep were the most susceptible to poisoning by subcutaneous injection of larkspur extract with decreasing susceptibility in hamsters, mice and rats, but sheep had least susceptibility when comparing response to oral (by gavage) doses. Also, death occurred rapidly after gavage as compared with subcutaneous doses in mice, hamsters and rats, but was nearly the same for sheep. We conclude that, of the animals tested, mice would be the best choice for a bioassay of the toxicity of larkspur because of their high susceptibility, rapid response time, and small dose requirement.

Description of a scale for rating the clinical response of cattle poisoned by larkspur.

Larkspur poisoning is a major cause of acute death of cattle on mountain and high plains rangelands of western United States. A nonlethal method to quantify dose response in cattle is needed to better estimate the toxicity of larkspur plants and the response of cattle to larkspur poisoning and to provide a basis for reference during studies. A numerical system of rating the clinical signs of larkspur poisoning was developed and used to describe the response of 10 Hereford cows given a repeated single daily dose of larkspur (Delphinium occidentale x barbeyi) by gavage. Larkspur poisoning resulted from a short-term cumulative effect, and a statistically significant increase in score was essentially maximal by 4 days. At the dose given, this effect did not persist for more than 4 days after cessation of dosing. Poisoning was most severe between 5 and 9 hours after dosing. Early signs of poisoning can be subtle and sometimes brief. The effect of larkspur poisoning can be exacerbated temporarily by exertion. Therefore, cattle could probably repeatedly consume an otherwise toxic daily dose, without manifesting marked signs of poisoning, if consumption decreased to a sufficient degree intermittently at 2- to 4-day intervals.

Premature bovine parturition induced by ponderosa pine: effects of pine needles, bark and branch tips.

Three components of Ponderosa pine trees were administered via gavage to pregnant cows to determine their ability to induce premature parturition. When tips of branches, bark or needles were administered (2.7 kg/day) starting at 250 d of pregnancy, early parturition was induced in an average of 3.4, 5.0 and 9.1 d, respectively, compared to 31.8 d for water gavaged controls (P less than 0.01). Less pine material was required to induce parturition with tips and bark (9.4 and 11.2 kg/cow, respectively) than with needles (25.0 kg/cow P less than 0.05). Cows fed pine material retained fetal membranes longer after parturition; 13.0 d for needles, 10.5 d for bark and greater than 3.0 d for tips versus less than 0.5 d for controls (P less than 0.01). However, 2 of the cows fed tips died within 48 hours after parturition with fetal membranes intact and the other 2 cows fed tips became depressed, pyrexic and emaciated. They survived after extended veterinary care with antibiotic and fluid therapy. Administration of pine materials modified serum progesterone concentration profiles; there was significant elevation in progesterone 1-3 days after pine material was administered. Subsequently, pine material induced a premature decline in progesterone levels prior to parturition, which occurred more rapidly in cows fed bark and tips suggesting a dose response relationship. Pine material also modified serum cortisol concentration profiles; the main difference was a prolonged elevation in cows receiving tips. Branch tips and bark from Ponderosa pine are more potent in inducing parturition than needles.

Multiple congenital contractures (MCC) and cleft palate induced in goats by ingestion of piperidine alkaloid-containing plants: reduction in fetal movement as the probable cause.

Fetal movement, observed by ultrasound imaging, was significantly reduced (P less than or equal to 0.001) in pregnant goats gavaged with Conium seed and Nicotiana glauca and temporarily reduced with fresh Conium plant. Conium seed and Nicotiana glauca induced cleft palate and multiple congenital contractures in 100% of the kids born to pregnant goats gavaged with these plants. Multiple congenital contractures included torticollis, scoliosis, lordosis, arthrogryposis, rib cage anomalies, over extension, and flexure and rigidity of the joints. However, in goats gavaged with fresh Conium plant, fetal movement was inhibited for only about 5 hours after each individual dosage and gradually returned to control levels 12 hours after dosing. Fetal malformations in this group were limited from modest to moderate contractures of the front limbs, which resolved by 8-10 weeks post partum. No cleft palates were induced. Fetal movement was not inhibited in goats fed Lupinus caudatus and no cleft palates or multiple congenital contractures were induced in their offspring. The duration of the reduction in fetal movement appears to be an important factor in the severity and permanence of the deformities, particularly with cleft palate, spinal column defects, and severe joint deviation and fixation.

Radio ultrasound observations of the fetotoxic effects in sheep from ingestion of Conium maculatum (poison-hemlock).

Fetal movement in pregnant ewes gavaged with Conium maculatum (poison-hemlock) was reduced significantly, but temporarily. Fetal movement was observed by radio ultrasound at 45, 54 and 60 days of gestation in control ewes and on days 45, 54, and 60 of gestation immediately before and 1 hour following poison-hemlock feeding in treated ewes. Fetal movement was significantly reduced (P less than 0.01) 1 hour after poison-hemlock administration, but returned to normal within 18 hours post treatment. At parturition seven of eleven lambs born to seven treated ewes had varying degrees of front limb abnormalities. Modest to moderate flexure of the carpal joints, some lateral deviation in the front limbs at the pastern joint and kinked tails were observed. These malformations were transient and resolved spontaneously by 8 weeks after lambing.

Dietary calcium and phosphorus and seizure susceptibility of magnesium deficient rats.

Convulsions are characteristic of magnesium deficiency and hypocalcemia. In this study, weanling rats were fed magnesium deficient diets with varying concentrations of calcium and phosphorus. Diets were either normal (Mg =) or low (Mg-) in magnesium and were either low (Ca- or P-), normal (Ca = or P =) or high (Ca+ or P+) in calcium or phosphorus. After consuming the diets for 17 days, the rats were tested for audiogenic seizures and blood was then drawn for serum mineral analyses. Rats fed Mg-Ca = P =, Mg-Ca = P-, Mg-Ca+P = or Mg-Ca+P+ diets had high incidences of seizures. Those fed Mg-Ca-P =, Mg-Ca-P-, Mg-Ca = P+, Mg-Ca-P+ or Mg-Ca+P- diets had low incidences of seizures. In general, animals with low serum magnesium and calcium levels and high serum potassium levels were susceptible to audiogenic seizures. In this model, serum magnesium level is the most important determinant of seizure susceptibility, followed by calcium and potassium.

Ultrasonographic imaging to monitor fetal and placental developments in ewes fed locoweed (Astragalus lentiginosus).

Ultrasonographic imaging was used to monitor the effects of locoweed (Astragalus lentiginosus) on fetal, placental, and cotyledonary developments in pregnant ewes and proved to be a useful noninvasive method of monitoring the effects of locoweed poisoning on fetal and placental development. Ultrasonographic imaging may be a good research technique to observe the effects of toxicants on fetal movement, fetal heart action, and growth and development of the fetus and placenta. Known effects of locoweed poisoning in pregnant ewes, such as fluid accumulation in the placenta (hydrops allantois, hydrops amnii), altered cotyledonary development, and fetal death were observed with ultrasonographic imaging. A previously unknown effect of locoweed on fetal heart action also was observed. Locoweed decreased fetal heart rates, caused cardiac irregularity, and decreased the strength of heart contractions. All ewes, except No. 3525, fed locoweed aborted. At necropsy, aborted fetuses had hypertrophy of the heart, right ventricular dilatation, rounded at the apex of the heart, and generalized edema.

Soil and plant water relations in a crested wheatgrass pasture: response to spring grazing by cattle.

Few field studies have attempted to relate effects of actual livestock grazing on soil and plant water status. The present study was initiated to determine the effects of periodic defoliations by cattle during spring on soil moisture and plant water status in a crested wheatgrass (Agropyron cristatum (L.) Gaertn. and A. desertorum (Fisch. ex Link) Schult.) pasture in central Utah. Soil moisture in the top 130 cm of the soil profile was depleted more rapidly in ungrazed plots than in grazed plots during spring and early summer. Soil moisture depletion was more rapid in grazed plots in one paddock after 1 July due to differential regrowth, but there was no difference in soil water depletion between plots in another paddock during the same period. This difference in soil water depletion between paddocks was related to a difference in date of grazing. Although more water had been extracted from the 60 cm to 130 cm depths in ungrazed plots by late September, cumulative soil moisture depletion over the entire 193 cm profile was similar in grazed and ungrazed plots. Prior to 1 July, grazing had no effect on predawn leaf water potentials as estimated by a pressure chamber technique; however, after 1 July, predawn leaf water potentials were lower for ungrazed plants. Midday leaf water potentials were lower for grazed plants before 1 July, but did not differ between grazed and ungrazed plants after 1 July. A 4- to 8-day difference in date of defoliation did not affect either predawn or midday leaf water potentials. The observed differences in water use patterns during spring and early-summer may be important in influencing growth and competitive interactions in crested wheatgrass communities that are subject to grazing by domestic livestock.

Differential Reaction of Alfalfa Cultivars to Meloidogyne hapla and M. chitwoodi Populations.

Meloidogyne hapla reproduced and suppressed growth (P < 0.05) of susceptible Lahontan and Moapa alfalfa at 15, 20, and 25 C. At 30 C, resistant Nevada Syn XX lost resistance to M. hapla. M. hapla invaded and reproduced on Rhizobium meliloti nodules of Lahontan and Moapa, inducing giant cell formation and structural disorder of vascular bundles of nodules without disrupting bacteroids. At 15, 20, and 25 C a M. chitwoodi population from Utah reproduced on Lahontan, Moapa, and Nevada Syn XX alfalfa, suppressing growth (P < 0.05). Final densities of the Utah M. chitwoodi population were greater (P < 0.05) than those of Idaho and Washington State populations on Lahontan at 15 and 25 C and on Nevada Syn XX at 15 C, but were less consistent and smaller (P < 0.05) than those of M. hapla on Lahontan and Moapa at 20 and 25 C. Inconsistent reproduction of the Utah M. chitwoodi population on alfalfa suggests the possible existence of nematode strains revealed by variability in alfalfa resistance. No reproduction or inconsistent final nematode population densities with no damage were observed on Lahontan, Moapa, and Nevada Syn XX plants grown in soil infested with Idaho and Washington State M. chitwoodi populations.

Native seed preferences of shrub-steppe rodents, birds and ants: the relationships of seed attributes and seed use.

This study established the preferences of shrubsteppe granivores among seeds of 6 common sagebrushsteppe plants and related the preferences observed to physical and nutritional attributes of the seeds. Seeds of big sagebrush (Artemisia tridentata), cheatgrass (Bromus tectorum), Indian ricegrass (Oryzopsis hymenoides), western wheatgrass (Pascopyrum smithii), bitterbrush (Purshia tridentata) and green needlegrass (Stipa viridula) were placed in groups of petri dishes designed such that seed removal could be ascribed to either diurnal vertebrates, nocturnal vertebrates or ants. Though absolute quantities of seeds removed varied among the 3 granivore classes, calculations of preference based on weights of each seed species removed by each granivore class indicated that all 3 ranked the seeds similarly. Preference hierarchies of the 3 granivore classes were highly positively correlated with both calories per seed and % soluble carbohydrate of the seeds. The first correlation supports a basic prediction of optimal foraging theory -that foragers should maximize energy intake per unit time spent foraging. Both correlations emphasize the role of seed nutritional qualities in granivore seed selectivity in that soluble carbohydrate is a water-efficient energy source and its percentage is a good indicator of the digestible energy available in a food item. A corollary experiment comparing granivore use of an exotic seed (millet [Panicum miliaceum]) and a preferred native seed (Oryzopsis) demonstrated a distinct preference for the exotic. Since millet seeds are particularly high in % soluble carbohydrate, this result reinforced the apparent value of this nutritional attribute as a predictor of granivore seed preference. Among many seed resource characteristics upon which granivore seed selectivity might operate, our results indicate that individual species' nutritional composition may be particularly important. Thus, inferences about seed selectivity and resource partitioning among arid-land granivores should be interpreted with caution, especially those based on experiments using seed introductions, since the influence of seed nutritional attributes has not been widely acknowledged heretofore.

Fasting and ketogenic diet effects on audiogenic seizures susceptibility of magnesium deficient rats.

Because fasting and ketogenic diets decrease seizure susceptibility in epileptics, their anticonvulsant effects were studied using sound-induced seizures in the magnesium-deficient rat. Fasting markedly depressed seizure incidence and severity but did not affect latency (sec to seizure onset). High-fat diet increased incidence of audiogenic seizures and seizure severity, and decreased latency. Gavage of medium chain triglyceride, beta-hydroxybutyrate or glucose did not affect seizure incidence, seizure severity or latency. Nonspecific excitability level was not associated with treatment nor with seizure incidence, severity or latency time.

Effects of Temperature and Root Leachates on Embryogenic Development and Hatching of Meloidogyne chitwoodi and M. hapla.

At 20 C the duration of the embryogenic development of Meloiclogyne chitwoodi and M. hapla was about 20 days. At 10 C the embryogenic development was 82-84 days for M. chitwoodi and 95-97 days for M. hapla. The effect of distilled water and root leachates of potato cv. Russet Burbank, tomato cv. Columbian, and wheat cv. Hyslop on the hatching of eggs of the two root-knot nematode species was investigated at 4, 7, 10, 15, 20, and 25 C (+/- 1 C). Cumulative egg taatch was no greater in root leachates titan in distilled water, but temperature did significantly affect egg hatch (P = 0.05). Less than 1% of the eggs of both nematode species hatched at 4 C. The percent cumulative hatch at 10 C was significantly less (P = 0.05) than at higher temperatures for both nematodes and significantly more (P = 0.05) M. chitwoodi eggs hatched than did M. hapla eggs. At 15 G the percent cumulative hatch of both species was significantly lower (P = 0.05) than that at 20 and 25 C. The percent cumulative egg hatch of two species did not differ at 25 C, but was higher (P = 0.05) at 25 C than at 20 C. At 7 C the emergence of M. chitwoodi juveniles was about seven times (P = 0.01) greater than that of M. hapla in distilled water.