Composition and cheese making ability of milk from Friesian and Normandy cows. 1. Breeding effects

Abstract

This study involves 1663 samples of milk produced by the two breeds kept simultaneously, during 2 seasons (spring - winter 1985), in 3 areas of the Normandy province (Cotentin, Bocage, Caux). There is a direct relationship between the time for the curds to become firmer and their degree of firmness. This depends mainly on the levels of protein, calcium fat and lactose, and on the diameter of casein micelles. Coagulation starting times may differ, which depends mainly on lactose and cell contents of the milk and rather less on protein and fat contents. The two breeds show large differences for most variables, the Normandy breed producing less milk than the Friesian one (- 4 kg/day), but showing higher protein (+ 2 to 2.5 ‰), fat (+ 2 to 3 ‰) and calcium (+ 0.1 ‰) levels, smaller casein micelles and far superior technological tests (relative differences of - 26 % for coagulation starting times, - 72 % for the time for curds to become firmer, + 20 % for the firmness of the curds). The effect of season, feeding and, to a lesser degree, the stage of lactation, are very high, with winter milks being poor in nitrogenous and mineral components and greatly inferior to « spring » quality milk with respect to cheese making ability. The two breeds and the two periods are distinguished better by the technological tests than by the levels of the various contents, showing the effects of breed and season towards the cheese-making ability of milks and suggesting that some milk parameters, not taken into account in this study (nature of caseins, chemical form of minerals, pH...) have a role in determining technological properties. Different areas showed few significant effects on the milk composition (less protein and fat in Caux area) and no effect at all on the technological tests ; the inter-farms production systems variability is higher than the inter-areas one.