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American Journal of Potato Research - 相似文献
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Sorghum ergot produces dihydroergosine (DHES) and related alkaloids, which cause hyperthermia in cattle. Proportions of infected panicles (grain heads), leaves and stems were determined in two forage sorghum crops extensively infected 2 to 4 weeks prior to sampling and the panicles were assayed for DHES. Composite samples from each crop, plus a third grain variety crop, were coarsely chopped and half of each sealed in plastic buckets for 6 weeks to simulate ensilation. The worst-infected panicles contained up to 55 mg DHES/kg, but dilution reduced average concentrations of DHES in crops to approximately 1 mg/kg, a relatively safe level for cattle. Ensilation significantly (P = 0.043) reduced mean DHES concentrations from 0.85 to 0.46 mg/kg. 相似文献
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Effect of a valine residue at codon 352 of the VP2 capsid protein on in vivo replication and pathogenesis of Aleutian disease parvovirus in mink 总被引:4,自引:0,他引:4
Stevenson MA Fox JM Wolfinbarger JB Bloom ME 《American journal of veterinary research》2001,62(10):1658-1663
OBJECTIVE: To determine whether a group of 3 genetic differences in the nonstructural protein (NS1) or 1 genetic difference in the structural protein (VP2) of Aleutian disease parvovirus (ADV) is responsible for an increase in the in vivo replication and pathogenicity of G/U-8, a chimera of ADV-G (nonpathogenic) and ADV-Utah (pathogenic), compared with G/U-10. ANIMALS: 32 eight-month-old female sapphire mink (Mustela vison). PROCEDURE: Chimeric viruses were constructed, propagated in vitro, and used to inoculate mink. Antiviral antibody responses, presence of serum viral nucleic acid, and serum gamma globulin concentrations were monitored for 120 days following inoculation. Histologic examination of the liver, kidneys, spleen, and mesenteric lymph nodes was performed after necropsy. RESULTS: A chimera containing only the 3 amino acid substitutions in NS1 did not elicit measurable responses indicative of replication or pathogenicity in inoculated mink. Serum antiviral antibody responses, frequency of detection of viral nucleic acid in serum, gamma globulin response, and histologic changes in mink inoculated with chimeras containing a valine residue at codon 352 (352V) of VP2 capsid were increased, compared with values from mink inoculated with chimeric viruses that did not contain 352V. CONCLUSIONS AND CLINICAL RELEVANCE: A valine residue at codon 352 in the VP2 capsid protein of ADV affects in vivo viral replication and pathogenicity. This amino acid may be part of an incompletely defined pathogenic determinant of ADV. Further characterization of the pathogenic determinant may allow future development of focused preventive and therapeutic interventions for Aleutian disease of mink. 相似文献
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This paper presents an epidemiological investigation of Ontario Ministry of Natural Resources Fish Health Laboratory data from 1981 to 1997, to determine whether fish species and age were associated with lot-level detection of Aeromonas salmonicida and Yersinia ruckeri in hatchery fish. In stepwise logistic regression, the species brook trout and back-cross (lake trout crossed with the hybrid “splake”) were more likely to test A. salmonicida-positive compared to all other species reared in the hatcheries. Similarly, the species brook trout was significantly more likely to test Y. ruckeri-positive compared to all other species. For both pathogens, the 1–5-month age group was associated significantly with detection. These findings suggest that purposive sampling of higher-risk fish lots could increase the likelihood of detecting both study pathogens. 相似文献
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AIM: To determine the effect of calcium supplementation of dairy cattle after calving on serum concentrations of calcium, magnesium, and phosphorous after calving, and on reproductive and productive performance in the following lactation. METHODS: This was a double-blind randomised clinical trial using 356 dairy cows of parity 3 or greater from six seasonally calving commercial dairy herds. Cows were randomly assigned to a treatment and control group. The treatment group received two doses of 380 ml of calcium chloride in oil (49 g of elemental calcium); the first dose was given as soon as practical after calving and the second 12 hours later. Control cows received 380 ml of a placebo using the same treatment regime. Treatment and control cows had blood samples taken during the first 7 days after calving to determine serum calcium, magnesium and phosphorous levels. Treatment and control cows were monitored throughout the lactation to measure production and reproductive performance. RESULTS: Treatment had no effect on PSM to first service intervals. Treatment significantly reduced PSM to conception intervals in only one of the four herds with data available for analysis (p = 0.09). There was no difference between treatment groups for adjusted corrected milk yield calculated from the first herd test milk yield (p = 0.93) or 305-day milk solids production (p = 0.19). CONCLUSION: Further studies are required to identify reasons for the between-herd effectiveness of calcium chloride treatment in improving fertility. 相似文献
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Four pubertal (25 wk) crossbred boars were used to evaluate the role of the photoperiod in the organization of secretion of cortisol and melatonin throughout a 24-hr period. Boars were exposed to a 16-hr photoperiod in an environmentally controlled room and temperature was kept constant at 22 C. For the first 15 d, the onset of the photophase (light phase) and scotophase (dark phase) was 0200 hr and 1800 hr, respectively (ON2). During the final 15 d, the onset of the photophase and scotophase was advanced by 6 hr (0800 hr and 2400 hr, respectively; ON8). Samples of serum were obtained from catheterized boars at hourly intervals for 24 hr between the 14th to 15th d in both ON2 and ON8 photoperiods. Samples of serum were frozen and later assayed for cortisol and melatonin. The data were normalized to the clock time of onset of the photophase, fit to polynomial equations, and the profiles of cortisol and melatonin in ON2 and ON8 were tested for heterogeneity of regression. A circadian rhythm of cortisol was observed in both ON2 and ON8 and the fitted profiles were parallel, suggesting that the rhythm had shifted with the 6-hr shift in lights-on, lights-off. Generally, higher concentrations were observed during the late subjective evening and scotophase, whereas lower concentrations occurred about 6 to 10 hr after onset of the photophase. Although the profiles of melatonin did not differ in ON2 and ON8, there was no evidence of a nocturnal rise in melatonin in either treatment. It is suggested that some characteristic of the photoperiod organizes the circadian rhythm of cortisol in boars, but melatonin is not secreted in a rhythmic fashion in long photoperiods. 相似文献