Chemical composition of herd milk and farming system in the Massif Central

Abstract

Twenty-five farms in Auvergne were followed up in 1998. Four studies, performed during the different seasons, made it possible to characterise the management of dairy cows. Five samples were taken from cattle milk, 2 in winter and 3 at grazing, in order to analyse nitrogen fractions (paracasein, urea), lactose and mineral content (calcium, phosphorus and citrates in milk and serum), fat composition, proteolytic enzyme activities and pH. The 89 herd milk samples whose herd mean lactation stage lasted between 2 and 7 months formed six classes of milk which contrasted for all the analysed characteristics. Season, race and feeding are the main factors accounting for variation in the chemical composition of milk. Three classes deserve our attention. The first one groups together milks produced during the winter generally by herds fed with fermented forage; they present the less favorable characteristics. Conversely, another class assembles milks with high levels of protein, minerals and polyinsatured fatty acids. These milks are produced by Montbeliard herds at the end of summer. Finally, a class of milks, produced by Salers herds, presents a very low level of fat concentration and very weak proteolytic enzyme activities. Cheese-making properties of these different types of milk must be quantified.