Du Preez, J.H.Willemse, J.J.C.Van Ark, H.Verwoerd, Daniel Wynand2013-12-092013-12-0920131994Du Preez, JH, Willemse, JJC & Van Ark, H 1994, 'Effect of heat-stress on conception in a dairy-herd model in the Natal highlands of South Africa', Onderstepoort Journal of Veterinary Research, vol. 61, no. 1, pp. 1-6.0330-2465http://hdl.handle.net/2263/32737The 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.Regression models are proposed for predicting conception rate in a dairy herd under South African and especially Natal conditions. Conception rate (CR%) was related to mean monthly temperature-humidity index (THI) by curvilinear regression equation model; CR% = -812,7 + 28,61THI - 0,2322THI² (P = 0,061), and by linear regression equation model; CR% = 188,0 - 1,906THI (P = 0,023). Conception rate was related to numerical month of the year (M) by: CR% = 44,34 + 6,168M - 0,428M² (P = 0,1 06). Further investigations to test the proposed regression models under various dairy-herd conditions and to improve reproduction in South African dairy herds are needed.en© ARC-Onderstepoort (original). © University of Pretoria. Dept of Library Services (digital).Veterinary medicineFriesian cattleLidgettonVeterinary medicine -- South AfricaHeat -- Physiological effectArticle