测定谷物含水率的声学方法     

Frie.  TL 《农机质量与监督》1989,(4):11-14

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Use of Diet Crossover to Determine the Effects of β‐glucan Supplementation on Immunity and Growth of Nile Tilapia,Oreochromis niloticus     

Thomas L. Welker  Chhorn Lim  Mediha Yildirim‐Aksoy  Phillip H. Klesius 《Journal of the World Aquaculture Society》2012,43(3):335-348

Juvenile Nile tilapia were fed either a basal (control) diet (n = 6 aquaria) or a diet supplemented with 1 g/kg β‐glucan (n = 24 aquaria) for 4 wk. At the end of this period, fish receiving β‐glucan were continued on the same diet (n = 12 aquaria) or switched to the control diet (n = 12 aquaria) for 2 wk. After 6 wk, tilapia continuously fed the β‐glucan supplemented diets had improved weight gain and feed efficiency than those fed the control diet uninterrupted or switched from the β‐glucan diet to the control after 4 wk. Feeding tilapia β‐glucan for 4 wk and then switching to the basal diet for 2 wk caused a significant increase in the respiratory burst of polymorphonuclear lymphocytes (17.77 × 10³ units/1000 white blood cells [WBC]) compared to catfish fed the control diet (13.50 × 10³ units/1000 WBC) or the β‐glucan diet continuously (13.57 × 10³ units/1000 WBC), but other immune parameters were unaffected. Tilapia were then challenged with Streptococcus iniae. The two groups were divided again (n = 6 aquaria) postchallenge and continued on the same diet or switched to the other diet (β‐glucan or control) for another 3 wk. No differences in survival to S. iniae infection occurred between dietary groups.  相似文献   

Experimental infection of normal and immunosuppressed pigs with Pseudomonas pseudomallei   总被引：1，自引：0，他引：1  

AD THOMAS  JC FORBES-FAULKNER  TL D''ARCY  JH NORTON  D HOFFMANN 《Australian veterinary journal》1990,67(2):43-46

A single dose of 5 x 10(8) bacilli of Pseudomonas pseudomallei by intratracheal injection resulted in acute (21 cases) or chronic (19 cases) melioidosis in 40 of 48 pigs. Fifteen (10 acute and 5 chronic) had been immunosuppressed by cyclophosphamide before inoculation. The major clinical signs were initial fever, marked neutrophilia and, in the acute cases, respiratory distress. There were no signs of the nasal and ocular discharge, paresis or diarrhoea seen in acute cases in south-east Asia. The cyclophosphamide treatment caused a significant decrease in the neutrophil count by 7 d after inoculation in all 15 immunosuppressed pigs, and all were culture positive at necropsy. Eight of the 33 non-treated pigs were culture negative at necropsy. Pigs overcoming the initial phase of infection had more abscess-like nodules that were bacteriologically sterile at necropsy than the pigs with acute cases of melioidosis. P. pseudomallei was isolated predominantly from the spleen, lungs and the injection site. Although only one strain was used in this study, it is likely that Australian strains of P. pseudomallei are not as virulent as the south-east Asian isolates.  相似文献   

Green algal carotenoids and yellow pigmentation of rainbow trout fish     

C. Welker  P. De Negro  M. Sarti 《Aquaculture International》2001,9(1):87-93

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Oxidative stress in juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum)     

Thomas L Welker  & James L Congleton 《Aquaculture Research》2004,35(9):881-887

Juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), were held in 8–11°C freshwater, starved for 3 days and subjected to a low‐water stressor to determine the relationship between the general stress response and oxidative stress. Lipid peroxidation (LPO) levels (lipid hydroperoxides) were measured in kidney, liver and brain samples taken at the beginning of the experiment (0‐h unstressed controls) and at 6, 24 and 48 h after application of a continuous low‐water stressor. Tissue samples were also taken at 48 h from fish that had not been exposed to the stressor (48‐h unstressed controls). Exposure to the low‐water stressor affected LPO in kidney and brain tissues. In kidney, LPO decreased 6 h after imposition of the stressor; similar but less pronounced decreases also occurred in the liver and brain. At 48 h, LPO increased (in comparison with 6‐h stressed tissues) in the kidney and brain. In comparison with 48‐h unstressed controls, LPO levels were higher in the kidney and brain of stressed fish. Although preliminary, results suggest that stress can cause oxidative tissue damage in juvenile chinook salmon. Measures of oxidative stress have shown similar responses to stress in mammals; however, further research is needed to determine the extent of the stress–oxidative stress relationship and the underlying physiological mechanisms in fish.  相似文献   

Nutritional factors in bovine gastrointestinal disease     

C N Niederman  C D Thatcher  B Welker 《Veterinary Clinics of North America: Food Animal Practice》1990,6(2):265-306

Gastrointestinal disorders may be prevented through proper nutrition. Attention should be placed on establishing optimum feeding programs for cattle in all stages of the life and production cycle. Normal reticuloruminal development in calves and maintenance of gastrointestinal function in adult cattle is dependent upon adequate nutrition. Nutrition is also an important part of therapy of many gastrointestinal disorders.  相似文献   

Role of land-surface changes in arctic summer warming   总被引：2，自引：0，他引：2  

Chapin FS  Sturm M  Serreze MC  McFadden JP  Key JR  Lloyd AH  McGuire AD  Rupp TS  Lynch AH  Schimel JP  Beringer J  Chapman WL  Epstein HE  Euskirchen ES  Hinzman LD  Jia G  Ping CL  Tape KD  Thompson CD  Walker DA  Welker JM 《Science (New York, N.Y.)》2005,310(5748):657-660

A major challenge in predicting Earth's future climate state is to understand feedbacks that alter greenhouse-gas forcing. Here we synthesize field data from arctic Alaska, showing that terrestrial changes in summer albedo contribute substantially to recent high-latitude warming trends. Pronounced terrestrial summer warming in arctic Alaska correlates with a lengthening of the snow-free season that has increased atmospheric heating locally by about 3 watts per square meter per decade (similar in magnitude to the regional heating expected over multiple decades from a doubling of atmospheric CO2). The continuation of current trends in shrub and tree expansion could further amplify this atmospheric heating by two to seven times.  相似文献   

Therapeutic strategies involving antimicrobial treatment of disseminated infections in food animals     

G F Hoffsis  F H Welker 《Journal of the American Veterinary Medical Association》1984,185(10):1214-1216

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Tracking the long-term decline and recovery of an isolated population     

RL Westemeier  JD Brawn  SA Simpson  TL Esker  RW Jansen  JW Walk  EL Kershner  JL Bouzat  KN Paige 《Science (New York, N.Y.)》1998,282(5394):1695-1698

Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens.  相似文献   

Effects of Yeast Oligosaccharide Diet Supplements on Growth and Disease Resistance in Juvenile Nile Tilapia,Oreochromis niloticus     

Richard A. Shelby  Mediha Yildirim-Aksoy  Thomas L. Welker  Phillip H. Klesius 《Journal Of Applied Aquaculture》2013,25(1):61-71

Commercially available yeast and yeast subcomponents consisting mainly of β-glucan or oligosaccharide feed additives were added to diets of juvenile (12–18g) Nile tilapia (Oreochromis niloticus) at rates recommended by suppliers. Three experiments were conducted following a basic protocol with varied rates of supplementation, duration of feeding, and stocking densities. Experimental diets were fed twice daily to apparent satiation for a period of two or four weeks, at the end of which feed consumption and weight gain were measured. Following the experimental feeding period, serum components, including protein and immunoglobulin concentrations, as well as lysozyme and complement activities, were measured. A disease challenge was conducted with pathogenic isolates of Streptococcus iniae or Edwardsiella tarda. Weight gains were not significantly different in fish fed the supplemented diets when compared to the control diet. There were significant differences in fed intake within individual experiments; however, this effect was not consistent in all three experiments. Overall feed efficiency was not significantly affected by diet. There were no differences in serum components of fish sampled at two or four weeks. Fish fed the experimental diets did not have lower mortality or morbidity after disease challenge compared to fish fed the control diets. Specific antibody against S. iniae or E. tarda measured by ELISA did not reveal differences in the fish surviving the challenge. We conclude that the incorporation of these commercial yeast component products into the diet of juvenile Nile tilapia at these rates and for these feeding periods had no effect on growth, serum components, antibody responses, or survival following S. iniae or E. tarda infection.  相似文献