Technical note: The ability of mathematical models to describe the shape of lactation curves

Seven of the best-known mathematical models based on least squares linear r egression were fitted to data following the peaking (standard) lactation cu rve, termed type I, and a continuously decreasing lactation curve, termed t ype II. The Wood (1967) gamma function, the Cobby and Le du (1978) weighed least squares gamma function, quadratic and the Sikka (1950) model fitted t o both types of curve. In contrast, the Jenkins and Ferrell (1984) and the inverse polynomial model always produced curves of type I, whereas the Brod y et al. (1923) model always produced curves of type II. Data should be car efully examined to prevent the use of models unable to render the appropria te curve type described by yield data.