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 regression were fitted to data following the peaking (standard) lactation curve, termed type I, and a continuously decreasing lactation curve, termed type II. The Wood (1967) gamma function, the Cobby and Le du (1978) weighed least squares gamma function, quadratic and the Sikka (1950) model fitted to both types of curve. In contrast, the Jenkins and Ferrell (1984) and the inverse polynomial model always produced curves of type I, whereas the Brody et al. (1923) model always produced curves of type II. Data should be carefully examined to prevent the use of models unable to render the appropriate curve type described by yield data.