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61.
J.Vittrup Christensen 《Scientia Horticulturae》1979,10(2):155-165
A single-plant-plot design was found very suitable for a study of growth and yield effect of tree density, rectangularity and row orientation on a wide range of intra and inter-row planting-distances.Densities from about 250 to 40 000 trees per hectare were studied in 2 apple cultivars on 2 weak-growing rootstocks over a period of 8 years. On unpruned trees a maximum yield of 80 tons per hectare of ‘James Grieve’ and about 95 tons of ‘Spartan’ was recorded. At the highest densities these yields were reached 2–3 years after planting.As early as the second to third year the growth was restricted at densities over about 1000 trees per hectare. A higher yield per tree at medium densities than at lower densities for the first fruiting-years is supposed to be an effect of growth resulting in earlier fruiting.A high rate of rectangularity reduced the yield only on densities of 1200–1550 trees per hectare. The lack of a significant effect on lower and higher densities is discussed.The growth and yield of rows oriented North—South were 17% higher than of those oriented East—West. 相似文献
62.
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64.
J Christensen R T Fosse O J Halvorsen I Morild 《American journal of veterinary research》1987,48(11):1649-1657
Three anesthetic agents (equithesin, metomidate, and ketamine) combined with diazepam were tested in the domestic fowl. Laparotomy and thoractomy were possible with the equithesin/diazepam combination, but only laparotomy was possible with the metomidate/diazepam combination. The combination of ketamine/diazepam did not result in the depth of anesthesia required for surgical procedures. Repeated blood pressure and heart rate measurements were recorded by use of a modified noninvasive Doppler technique. Equithesin/diazepam was our combination of choice for long-duration surgical anesthesia. The depth of anesthesia could be modulated by increasing the dose of diazepam. Metomidate/diazepam was useful when short-term anesthesia was required. In contrast to equithesin/diazepam, the metomidate/diazepam combination provided unstable anesthesia of varying depth and duration. Adverse reactions with metomidate indicated caution when using this drug in chickens; the drug also caused marked bradycardia. Ketamine/diazepam combination cannot be recommended as an anesthetic agent for use in chickens. The combination may be useful for minor surgical procedures or treatment, but not for experimental procedures that involve major surgery. Diazepam alone had a slight tranquilizing effect. 相似文献
65.
S R Gooneratne A A Olkowski D A Christensen 《Canadian journal of veterinary research》1989,53(4):462-467
The effect of high dietary sulfur (S) supplementation on blood thiamine (B1) concentration, biochemical indices of liver, muscle and kidney damage and selected plasma electrolytes was studied in six sheep. Three of these sheep received an additional 230 mg thiamine/kg diet (Group 2). After approximately 2.5-3 weeks on this diet, all three sheep in the non-B1-supplemented group (Group 1) showed loss of appetite and developed mild neurological signs: depression, intermittent signs of excitation and head pressing. Increases in blood B1 concentration and plasma creatine kinase (CK) and aspartate aminotransferase (AST) were observed during this time in all affected animals. Clinical signs lasted only for two to five days. Sheep in group 2 were clinically normal throughout the experiment, but all of these animals also had elevated blood B1 concentrations and plasma CK activity at the 3 wk sampling. Plasma magnesium concentrations of group 1 sheep were elevated at the 2.5-3 wk and 6 wk samplings but they declined significantly (p less than 0.05) to low normal levels thereafter. Magnesium concentrations of group 2 sheep were low at the beginning but progressively increased during the course of the experiment. At necropsy, brain lesions suggestive of polioencephalomalacia (PEM) were observed in all sheep but were most marked in group 1. It is speculated that PEM may be caused by a direct toxic effect of S, S metabolites or B1 antimetabolites in the brain rather than by an in vivo B1 deficiency per se. 相似文献
66.
Dziva F Christensen H van Leengoed LA Mohan K Olsen JE 《Veterinary microbiology》2004,102(1-2):117-122
Atrophic rhinitis in pigs is rarely reported in Southern Africa. To determine the relationship between Pasteurella multocida clones from clinical cases of atrophic rhinitis, twenty-one strains were characterised by selected phenotypic and genotypic methods. Biochemical analysis classified 18 strains as P. multocida subspecies multocida, whilst the remainder were grouped into separate unassigned biotypes. Capsular groups A (16/21) and D (l/21) were found among the isolates by PCR. Four ribotype patterns were obtained following HpaII ribotyping, whilst random amplification of polymorphic DNA (RAPD) revealed three main clusters. However, subclusters were also noted for each RAPD cluster. Our results indicate that RAPD offers a better discrimination of strains than ribotyping and that none of the phenotypic characters were directly related to the genotypic clusters. 相似文献
67.
68.
Christensen NH 《New Zealand veterinary journal》2006,54(4):193-194
AIM: To investigate the serological status of Old English Game (OEG) cockerels for a range of infectious diseases of poultry. METHODS: Standard methods were used to screen serum collected from approximately 200 birds during routine dubbing operations, in 2004 and 2005. RESULTS: There was no serological evidence of infection with Newcastle disease, infectious bursal disease, or Salmonella Pullorum. Antibodies to infectious bronchitis virus, avian encephalomyelitis (AE) virus, Mycoplasma gallisepticum and Mycoplasma synoviae were detected. CONCLUSIONS AND CLINICAL RELEVANCE: The disease status of OEG birds is similar to that of commercial poultry. 相似文献
69.
Otim Onapa M Christensen H Mukiibi GM Bisgaard M 《Tropical animal health and production》2006,38(4):285-289
The role of ducks in the transmission of Newcastle disease virus (NDV) to free-range village chicken was investigated experimentally.
Newcastle disease (ND) seronegative ducklings reared in a pen were infected oronasally with velogenic NDV of intracerebral
pathogenicity index (ICPI) 1.8 isolated from outbreaks in village chickens in Uganda. A first group of 3-week-old ND seronegative
chicks was mixed with the ducks and they were kept together for 7 days. Both ducks and chicks were observed for ND clinical
signs and any mortality, and they were bled and their sera were tested for ND antibodies by haemagglutination inhibition (HI)
test. The chicks were removed, euthanized and examined for any ND lesions, while the ducks were transferred to a fresh pen
and a second group of chicks was introduced and observed and treated as above. The ducks and the chicks tested positive for
ND antibodies 7 days post infection and contact, respectively, but showed no clinical signs, post-mortem lesions or mortality.
The mean ND antibody titre of the second group of chicks was lower than for the first group. This study has shown that although
ducks can be infected with velogenic NDV, they do not show clinical signs but are able to transmit NDV to in-contact chicks.
Further investigations are needed of the lack of clinical signs in the in-contact chicks and how long the ducks remain infective. 相似文献
70.
Mayor D Korczak BM Christensen H Bisgaard M Frey J Kuhnert P 《Veterinary microbiology》2006,116(1-3):194-201
Strains of [Actinobacillus] rossii, [Pasteurella] mairii and [Pasteurella] aerogenes can be isolated from abortion in swine. The RTX toxin Pax has previously been found only in those [P.] aerogenes strains isolated from abortion. Nothing is known about RTX toxins in field isolates of the other two species. To gain insight into the distribution of selected RTX toxin genes and their association with abortion, PCR screening for the pax, apxII and apxIII operons on 21 [A.] rossii and seven [P.] mairii isolates was done. Since species can be phenotypically misidentified, the study was backed up by a phylogenetic analysis of all strains based on 16S rRNA, rpoB and infB genes. The pax gene was detected in all [P.] mairii but not in [A.] rossii strains. No apx genes were found in [P.] mairii but different gene combinations for apx were detected in [A.] rossii strains. Most of these strains were positive for apxIII, either alone or in combination with apxII. Whereas pax was found to be associated to strains from abortion no such indication could be found with apx in [A.] rossii strains. Phylogenetically [A.] rossii strains formed a heterogeneous cluster separated from Actinobacillus sensu stricto. [P.] mairii strains clustered with [P.] aerogenes but forming a separate branch. The fact that [P.] aerogenes, [P.] mairii and [A.] rossii can phylogenetically clearly be identified and might contain distinct RTX toxin genes allows their proper diagnosis and will further help to investigate their role as pathogens. 相似文献