CT CASE PRESENTED AS PART OF THE 1997 A.C.V.R. ORAL CERTIFICATION EXAMINATION: COMPUTED TOMOGRAPHY/MAGNETIC RESONANCE IMAGING ELECTIVE*     

John S. Mattoon  Michael A. Walker 《Veterinary radiology & ultrasound》1998,39(2):156-157

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MRI CASE PRESENTED AS PART OF THE 1997 A.C.V.R. ORAL CERTIFICATION EXAMINATION: COMPUTED TOMOGRAPHY/MAGNETIC RESONANCE IMAGING ELECTIVE*     

John S. Mattoon  Michael A. Walker 《Veterinary radiology & ultrasound》1998,39(2):154-155

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Effects of yard weaning and training on the behavioural adaptation of cattle to a feedlot     

K.H. Walker  L.R. Fell  L.A. Reddacliff  R.J. Kilgour  J.R. House  S.C. Wilson  P.J. Nicholls   《Livestock Science》2007,106(2-3):210-217

Two experiments were conducted to determine the effect of weaning in small yards, with or without a feed bunk training procedure, on the subsequent behaviour and performance of Bos taurus steers in a feedlot. A reduction in the incidence of bovine respiratory disease (BRD) was the primary objective. In each experiment, about 200 male beef calves (Angus × Hereford and Hereford) were separated from their mothers at 7–9 months of age and allocated to one of three matched weaning treatment groups. The treatments were (1) yard weaning with hay or silage, (2) yard weaning with hay or silage plus a novel handling procedure to train the animals to be able to find a grain ration in a trough, and (3) paddock weaning without supplement or handling according to common industry practice in southeastern Australia. Paddock weaning is the practice of abrupt separation of cows and calves followed by return to separate pasture paddocks, whereas yard weaning involves abrupt separation but the calves remain in the yards for several days. Experimental vaccines against the major BRD pathogens were given to half of each group 1–2 months prior to entry into a commercial feedlot. The yard weaned and yard trained cattle had a significantly greater weight gain in the first month and over the 90-day feeding period than the paddock weaned control groups. There was no difference between the groups in pre-feedlot weight gain. The yard trained groups showed greater feeding activity during the first few days in the feedlot, but were not significantly different in weight gain from yard weaned. The vaccination treatment also significantly improved the weight gain in the first month and over 80 days. The combination of yard weaning and vaccination produced the highest weight gains overall. There was consistently less morbidity in the yard weaned groups compared to paddock weaned controls. The morbidity in yard trained groups was intermediate between these two. Weaning in small yards and the appropriate use of effective BRD vaccines 1–2 months before feedlot entry are recommended for B. taurus feeder steers in southeastern Australia to minimise sickness and improve productivity in the feedlot. Associated benefits are reduced risks of antibiotic residues and of animal welfare problems.  相似文献   

Russell Harold Larson     

Louis W. Busse  Henry M. Darling  Glenn S. Pound  John C. Walker 《Potato Research》1962,5(2):129-130

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Addison's disease in a puppy     

J M Ruben  M J Walker  J A Longstaffe 《The Veterinary record》1985,116(4):91-93

Low serum cortisol levels in a young puppy, following adrenocorticotrophic hormone (ACTH) stimulation, were used to establish a clinical diagnosis of Addison's disease. This was likely to have been congenital although studies of adrenocortical function in close relatives showed no evidence of a genetic origin for the condition. Autoantibody to canine adrenal tissue was not present. Further investigations are necessary to establish the role of autoantibody in canine hypoadrenocorticism. The diagnosis of primary adrenocortical hypoplasia was confirmed at post mortem examination.  相似文献   

Two new species of ticks from southern Africa whose adults parasitize the feet of ungulates: Rhipicephalus lounsburyi n. sp. and Rhipicephalus neumanni n. sp. (Ixodoidea, Ixodidae)     

J B Walker 《The Onderstepoort journal of veterinary research》1990,57(1):57-75

Theiler & Robinson (1953) described, as Rhipicephalus follis D?nitz, 1910, a tick species originating from Dordrecht, Eastern Cape Province. A comparison of this tick with the syntypes of R. follis has now shown, though, that these 2 entities are different and it is therefore redescribed below as Rhipicephalus lounsburyi n. sp. Its adults parasitize sheep and various wild ungulates, attaching primarily on their feet. The hosts of the immature stages are still unknown. It has now been recorded from several places in the Eastern Cape; once in Natal, at Impendle, and in the Western Cape near Swellendam and between Clanwilliam and Graafwater. A second species, which has in the past been confused with the dassie parasite, Rhipicephalus distinctus Bedford, 1932, is described as Rhipicephalus neumanni n. sp. Its adults also attach on the feet of sheep and goats. The hosts of the immature stages are unknown. It has been widely recorded in the Bethanien and Keetmanshoop Districts of Namibia and, in South Africa, from scattered localities in the Karoo.  相似文献   

Testing the strength of corrosive sublimate solution in the treating of seed potatoes     

O. F. Walker 《American Journal of Potato Research》1932,9(5):75-77

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Morphology and rooting of shoots developing in response to decapitation and pruning of Caribbean pine   总被引：2，自引：0，他引：2  

R. J. Haines  S. M. Walker  T. R. Copley 《New Forests》1993,7(2):133-141

The effects of decapitation at various levels, combined with heavy pruning of remaining branches, were examined for Caribbean pine. This treatment stimulated the development of shoots with long primary needles at all levels in the crown of trees aged one, four and eight years. Although a significant positive relationship between primary needle length and rooting was demonstrated, the very juvenile appearance of these shoots was not a reliable guide to rooting. There was an over-riding effect on rooting of the ortet age × level in crown × decapitation height treatment. Decapitated trees provided shoots of higher rooting capacity than intact trees for the one and four, but not the eight year old trees. Shoots developing in the lower crown in response to decapitation and heavy pruning of four year old trees displayed a high level of rooting-equivalent to that of shoots from the decapitated and pruned one year old trees.  相似文献   

Black polyethylene mulch improves growth of plantation-grown loblolly pine and yellow-poplar     

R. F. Walker  S. B. Mclaughlin 《New Forests》1989,3(3):265-274

The effects of mulching with perforated black plastic, in combination with fertilization and induced mycorrhizal symbioses, on the growth of loblolly pine (Pinus taeda L.) and yellow-poplar (Liriodendron tulipifera L.) were studied in a plantation under intensive, short rotation management. Mulching effects on soil temperature were also examined in order to assess the potential influence of this treatment on temperature-dependent processes in soils affecting tree growth. Mulching significantly increased height and stem diameter growth of both species, attributable largely to improved water relations resulting from diminished soil surface evaporation and elimination of transpirational losses from competing vegetation. Mulching effects on soil temperature were insufficient to contribute substantially to the growth response exhibited by mulched trees. Multiple applications of urea-N promoted enhanced growth in both loblolly pine and yellow-poplar, an effect accentuated by mulching, but the field performance of trees inoculated in the nursery with selected mycorrhizal fungi was poor relative to that of the other treatments investigated.  相似文献   

Indentation of wood by wedges     

J. Doyle  J. C. F. Walker 《Wood Science and Technology》1985,19(1):47-55

Summary The deformation processes involved in wedge indentation of wood are described. The behaviour of wood is compared to that of an elastic-plastic solid and that of a cellular body. It approximates towards the former when its density is high and towards the latter when its density is low. The hardness of wood is examined as a function of density and of wedge angle.We wish to thank the University Grants Committee and the New Zealand Forest Service for supporting this work  相似文献