Effect of heat stress on conception in a dairy-herd model in the Natal highlands of South Africa.
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 +/- 28.61 THI - 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 = 0.106). Further investigations to test the proposed regression models under various dairy-herd conditions and to improve reproduction in South African dairy herds are needed.
Du Preez
J H
JH
Onderstepoort Veterinary Institute, South Africa.
Willemse
J J
JJ
Van Ark
H
H
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects*; D016014:Linear Models; D013312:Stress, Physiological / Q000662:veterinary*