Аннотация:ABSTRACT Monthly herd recording data from Friesian cows in south-east Queensland are used to evaluate 20 models of the lactation curve, 10 being drawn from the literature and 10 being original. The curve of Wood (1967) with equation y = a n b exp (–cn) ,and its modification y = a n fc /cosh (en) , generally gave the lowest values for the error mean square across all seasons of calving. However, the model which predicts a constant initial yield, followed by a linear decline, y = a for n =S c, y = a - b(n –c) for n > c , is as good as the previous two models for winter calving cows. Hence it is a useful representation of the lactation curve in south-eastern Queensland, where about 40% of cows are calved in winter. The inverse polynomial model y = nl(a + bn + en 2 ) is a useful model for lactations commencing in the summer months.
