Modulation of diversity by grazing and mowing in native tallgrass prairie   总被引：4，自引：0，他引：4  

SL Collins  AK Knapp  JMB riggs  JM Blair  EM Steinauer 《Science (New York, N.Y.)》1998,280(5364):745-747

Species diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically stressed grasslands enhanced biodiversity.  相似文献   

Efficacy of misoprostol in prevention of gastric hemorrhage in dogs treated with high doses of methylprednisolone sodium succinate.     

C R Rohrer  R C Hill  A Fischer  L E Fox  M Schaer  P E Ginn  V A Preast  C F Burrows 《American journal of veterinary research》1999,60(8):982-985

OBJECTIVE: To determine whether administration of misoprostol prevents gastric hemorrhage in healthy dogs treated with high doses of methylprednisolone sodium succinate (MPSS). ANIMALS: 18 healthy hound-type dogs of both sexes. PROCEDURE: All dogs were given high doses of MPSS (30 mg/kg of body weight, initially, then 15 mg/kg 2 and 6 hours later, and, subsequently, q 6 h for a total of 48 hours) IV. Dogs were assigned randomly to receive concurrent treatment with misoprostol (4 to 6 microg/kg, PO, q 8 h; n = 9) or an empty gelatin capsule (9). Gastroduodenoscopy was performed before and after treatment. Hemorrhage was graded from none (0) to severe (3) for each cardia, fundus, antrum, and duodenum. A total stomach score was calculated as the sum of the regional stomach scores. Food retention was recorded, and pH of gastric fluid was determined. Gastric and fecal occult blood was measured. RESULTS: Gastric hemorrhage was evident in all dogs after MPSS administration, and its severity was similar in both groups. Median total stomach score was 6 for misoprostol-treated dogs and 5.5 for dogs given the gelatin capsule. Difference in gastric acidity, frequency of food retention, and incidence of occult blood in gastric fluid and feces was not apparent between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of misoprostol (4 to 6 microg/kg, PO, q 8 h) does not prevent gastric hemorrhage caused by high doses of MPSS. Alternative prophylactic treatment should be considered.  相似文献   

The outbreak of equine influenza in England: January 1976.     

G R Thomson  J A Mumford  P R Spooner  R Burrows  D G Powell 《The Veterinary record》1977,100(22):465-468

Equine influenza type 2 infections occurred in the Newmarket areas in January 1976. The disease did not spread to any extent and while this may have been due to recent vaccination it was found that not all vaccinated horses were fully protected. The virus involved showed some antigenic drift from the prototype strain A/equine/Miami/1/63 (Heq 2 Neq 2).  相似文献   

Metoclopramide   总被引：2，自引：0，他引：2  

C F Burrows 《Journal of the American Veterinary Medical Association》1983,183(11):1341-1343

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Evaluation of the myoelectrical activity of the equine ileum infected with Strongylus vulgaris larvae   总被引：1，自引：0，他引：1  

C R Berry  A M Merritt  C F Burrows  M Campbell  J H Drudge 《American journal of veterinary research》1986,47(1):27-30

Five weanling ponies were subjected to an intensive 6-week deworming program after which 4 Ag-AgCl bipolar electrodes were implanted surgically on the distal ileum. For 3 hours each day for 5 consecutive days, ileal myoelectrical activity was recorded from fed ponies under 3 sequential conditions: preinoculation, after oral administration of 1,000 killed Strongylus vulgaris infective larvae (3 ponies), and after oral administration of 1,000 live S vulgaris infective larvae. Recordings were analyzed for slow wave frequency, percentage duration of phases I, II, and III of the migrating myoelectrical complex (MMC), and the frequency of distinct, rapidly migrating action-potential complexes within phase 2 of the MMC. After administration of live and killed infected 3rd-stage larvae, there was a marked increase in the number of disrupted phase III complexes, and a significant (P less than 0.001) increase in the number of migrating action-potential complexes. In addition, after inoculation of live 3rd-stage larvae, there was a significant increase (P less than 0.001) in the percentage of time that the MMC was occupied by prolonged periods devoid of spike activity (phase I). The results indicate that S vulgaris larval mucosal penetration and submucosal migration can cause changes in ileal myoelectrical activity that could cause colic, and that larval antigen alone within the lumen may disrupt ileal motility.  相似文献   

Experimental chloramphenicol intoxication in neonatal calves: intravenous administration     

G E Burrows  R D Tyler  S Sangiah  R D Keeton 《Research in veterinary science》1988,45(1):101-106

Chloramphenicol was administered intravenously for eight to 17 days to five newborn calves at a daily dosage of 100 mg kg-1. Haemodynamic, haematological, blood chemistry, serum enzyme, urinalysis and clinical responses were evaluated. High levels of serum chloramphenicol were observed throughout the study although a marked increase in elimination rate was seen with increasing age. The most severe adverse effects were severe hypotension following rapid intravenous administration and severe gastrointestinal dysfunction with diarrhoea accompanying prolonged high dosage. There appeared to have been a haematological effect in one calf, but it was of minor significance compared with the other effects.  相似文献   

In vitro assessment of the efficacy of erythromycin in combination with oxytetracycline or spectinomycin against Pasteurella haemolytica     

G E Burrows  P Ewing 《Journal of veterinary diagnostic investigation》1989,1(4):299-304

The effects of combining erythromycin (Ery) with oxytetracycline (Oxy) or spectinomycin (Sp) on Pasteurella haemolytica were evaluated in vitro using the chessboard (checkerboard) technique. These combinations were selected because all are drugs widely used in bovine respiratory disease treatment, and they represent possible sequential or complementary mechanisms of action. Using the recommended breakpoints of greater than 4 micrograms/ml for Ery, 16 micrograms/ml for Oxy, and 32 micrograms/ml for Sp, of the 33 P. haemolytica isolates, 32 were resistant to Oxy, 27 to Sp, and 14 to Ery. Based on the fractional inhibitory concentration index, Ery and Oxy in combination were synergistic or additive against 32 of 33 isolates. The combination of Ery and Sp was synergistic or additive against 27 of 33 isolates. No instances of antagonism were seen. When the effects were considered within the context of therapeutically achievable serum/tissue concentrations, the effects of Ery and Oxy in combination were only marginal. Thus, against P. haemolytica isolates, Ery and Sp appeared to represent an effective antimicrobial combination, whereas Ery and Oxy were only of marginal efficacy as a combination.  相似文献   

The prophylactic effect of corn supplementation on experimental nitrate intoxication in cattle     

G E Burrows  G W Horn  R W McNew  L I Croy  R D Keeton  J Kyle 《Journal of animal science》1987,64(6):1682-1689

Sodium nitrate was administered through rumen cannulae to produce NO-3 intoxication in four cows (382 to 445 kg body wt) fed prairie grass hay and a protein-mineral supplement. The cows were fed 0, 1.6 or 3.2 kg of dry rolled corn daily for 10 d prior to sodium nitrate administration. Sodium nitrate administration was followed by a marked increase in intraruminal NO-2 and NH3 and blood NO-2 and methemoglobin. Six of eight cows fed 0 and 1.6 kg of corn were given methylene blue to treat severe methemoglobinemia, while none of the cows fed 3.2 kg corn required such therapy. Feeding of 3.2 kg of corn protected against nitrate poisoning by reducing intraruminal nitrite and blood methemoglobin (P less than .05).  相似文献   

Early History of The Max Henry Memorial Library     

AK Sutherland 《Australian veterinary journal》1993,70(8):315-315

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Acute oxalate poisoning attributable to ingestion of curly dock (Rumex crispus) in sheep     

R J Panciera  T Martin  G E Burrows  D S Taylor  L E Rice 《Journal of the American Veterinary Medical Association》1990,196(12):1981-1984

Ten of 100 mature ewes were afflicted with acute oxalate toxicosis within 40 hours after being temporarily penned in a lot that contained considerable growing Rumex crispus (curly dock). Clinical signs of toxicosis included excess salivation, tremors, ataxia, and recumbency. Affected ewes were markedly hypocalcemic and azotemic. Oxalate crystals were not observed in urine. Gross postmortem lesions were minimal and nondiagnostic in 2 ewes that died peracutely, but perirenal edema and renal tubular degeneration were clearly observable in ewes euthanatized on the third day of toxicosis. Diagnosis of oxalate toxicosis was confirmed by histopathologic findings. Samples of Rumex spp contained 6.6 to 11.1% oxalic acid on a dry-weight basis, a concentration comparable with that in other oxalate-containing plants that have caused acute oxalate toxicosis.  相似文献