Modelling the kinetics of milk emission during machine milking in dairy ewes

The individual milking time is one of the aspects which affect the routine of milking in dairy ewes and the time to devote to this laborious task. The positive effect of an appropriate udder conformation in the reduction of manual interventions (stripping) during milking, have been clarified by numerous studies (Marie-Etancelinet al., 2001), leading to the development of appraisal methods of the udder which are being implemented in several breeding programs to improve udder morphology for milkability. On the other hand, a lack of knowledge on kinetics of the milk emission during machine milking still persists, mainly as a consequence of the difficulty of a large scale recording. Recently an automatic device able to follow individual kinetics of milk emission, developed by INRA (Ricardet al., 1995), was installed at the IZCS. The first purpose of this work was modelling the average shape of milk emission curves during machine milking by fitting an appropriate polynomial. Furthermore, since previous analysis showed that milk flow parameters, such as maximum or average milk flow, manifested an individual variability (Cartaet al., 2000), it was investigated whether this variability is also present in the shape of individual curves. With this goal a linear mixed model with random regression coefficients was implemented.