1990 Onderstepoort Journal of Veterinary Research, Volume 57, 1990
http://hdl.handle.net/2263/32326
2024-03-29T12:08:48ZFitting the Gompertz function to dose-response data of larval tick populations
http://hdl.handle.net/2263/41877
Fitting the Gompertz function to dose-response data of larval tick populations
Spickett, Arthur M.; Van Ark, H.
Verwoerd, Daniel Wynand
Samples of 6, 1st generation larval populations of Boophilus decoloratus, originating from field collected females, were subjected to increasing doses of the organophosphate acaricide, Dioxathion. The dose-response relationship for 3 populations showed random heterogeneity, where systematic deviations from the linear probit lines were observed for the other 3 populations. Logistic and Gompertz regressions were also fitted for all 6 populations. Probit regressions fitted best for 2 populations exhibiting heterogeneous responses. The logistic regression fitted best for 1 population with heterogeneous responses and 1 population with systematic deviating responses. The Gompertz regression fitted best for the 2 remaining populations exhibiting systematic deviating responses. The Gompertz function may be useful in describing the dose-response relationship obtained for certain acaricidal toxicity tests.
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1990-01-01T00:00:00ZPyridoxine (a vitamin B6) and its derivative pyridoxal as treatment for Albizia versicolor poisoning in guinea-pigs
http://hdl.handle.net/2263/41876
Pyridoxine (a vitamin B6) and its derivative pyridoxal as treatment for Albizia versicolor poisoning in guinea-pigs
Erasmus, G.L.
Verwoerd, Daniel Wynand
In the course of three experiments it was established that all the toxic effects of a lethal dose of Albizia versicolor pods (> 4,5g/kg) in guinea-pigs could be countered by concurrent subcutaneous injection of pyridoxine (10mg/kg). This treatment was also successful once severe symptoms had set in.
Pyridoxal, on the other hand, was found to be ineffective as a therapeutic agent. The fact that pyridoxal does not counter the action of the toxin indicates an atypical site of action by the toxin as regards the normal pathways which require vitamin B6 as a co-factor.
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1990-01-01T00:00:00ZEvaluation of the efficacy of anthelmintics against parafilariosis in cattle
http://hdl.handle.net/2263/41875
Evaluation of the efficacy of anthelmintics against parafilariosis in cattle
Carmichael, I.H.
Verwoerd, Daniel Wynand
Parafilariosis was first described in South Africa in 1964, thereafter being discovered at numerous localities in the country. When it became obvious that Parafilaria bovicola, for which no treatment was known, caused considerable economic losses, trials involving a series of compounds were conducted to identify candidate remedies. This paper describes an anthelmintic test for evaluating the efficacy of compounds for registration for field use.
Recovery of Parafilaria worms is impractical for anthelmintic testing, and consequently the lesion sizes of treated and control groups of cattle are compared statistically, using appropriate statistical tests.
The seasonal incidence of mature worm infection in cattle in South Africa is such that trials should commence after June and be completed before the end of January, allowing a lapse of 70 days between treatment and slaughter for resolution of the lesions. The presently available parafilaricidal compounds while of value for treating slaughter stock, when used alone will probably not be effective for control of infection in the field.
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1990-01-01T00:00:00ZHeat stress in dairy cattle and other livestock under southern African conditions. III. Monthly temperature-humidity index· mean values and their significance in the performance of dairy cattle
http://hdl.handle.net/2263/41874
Heat stress in dairy cattle and other livestock under southern African conditions. III. Monthly temperature-humidity index· mean values and their significance in the performance of dairy cattle
Du Preez, J.H.; Hattingh, P.J.; Giesecke, W.H.; Eisenberg, B.E.
Verwoerd, Daniel Wynand
Temperature-humidity index (THI) values applicable to South Africa and Namibia have been established during this investigation for each month of the year by means of computerized modelling and mapping techniques.
The data indicate that each year heat stress risk areas (HSRA's) expand from August to January and retract from February to July. The THI values classified according to the Livestock Weather Safety Index (LWSI) for lactating dairy cattle (LDC), suggest that, especially during November to March there is the risk of moderate to advanced heat stress in most South African dairy cows. This has important implications for their general health, udder health, production and reproduction. Careful planning of facilities and highly adaptable herd management are required to protect dairy cattle from heat stress.
The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.
1990-01-01T00:00:00Z