The Mathematical description of the lactation curve of ruminants: issues and perspectives

Test day records of milk production traits in the main livestock species reared for milk production were analyzed with several empirical mathematical models, with aim to identify suitable functions to fit different types of lactation curve shape. In the first chapter the modelling of extended lactations in dairy cows were analyzed. Several empirical mathematical models currently used to fit lactations with a function developed specifically for long patterns were compared. The second experimental contribution has approached a common problem when small ruminant lactation curves are modelled. In the specific case of the Sarda goat, the partial overlapping of altitude of location of flock with the partition into three different genetic subpopulation represents a further peculiarity. The third study was a investigation on the peculiar situation of the Massese breed ewes, where the intensification of reproductive cycle results in an alternate sequence of long and short lactations for each ewe. A frequent issue in modelling lactation curves is represented by relevant occurrence of atypical shapes, i.e. those that lacks of the peak yield and consist of a monotonically decreasing pattern.