Effect of nutritional level on composition and cheese making quality of milk from Holstein and Normandy cows

Abstract

The purpose of this trial was to determinate the related effects of nutrition and genetic factors on cow milk composition and cheese making quality in a 3 X 2 factorial design. In winter there were 3 genotypes (Normandy, standard Holstein and very high producing Holstein) and 2 nutritional levels (optimum and suboptimum (2 UFL lower)). The compositional quality and cheese making properties of milk produced by Normandy cows were better (+ 10 % for casein content, + 28 % for curd firmness and + 10 % for fresh corrected cheese yield) than those produced by the Holsteins. There was no difference in milk quality between the 2 Holstein genotypes. The quality of milk produced by cows submitted to optimal nutritional level was better than that produced by suboptimal level. The dietary effect in this trial appeared to be as important as the genetic effect. Normandy cows seem to be at least as sensitive as Holstein cows to underfeeding. In fact, due to the poor quality of the grass silage used in the suboptimal diet, the severity of underfeeding was greater for the Normandy cows. In April all cows were turned out to a good quality pasture, so the diet provided a good nutritional level. There was no difference in milk quality between the cows fed previously on optimal or suboptimal levels. This supports the view that the differences observed in winter were mainly due to differences in nutritional levels.