Protein content variation in milk from the dairy cow : results from surveys

Abstract

As milk protein content can affect the quantity and the quality of manufactured milk products, numerous surveys have recently been conducted in various french situations to determine some of the factors in herd management that influence milk protein content. Using these results, the objective of this study was to show the complexity of farm comparing to experimental data. The results of these surveys confirm that the mean annual protein content depends on genetic as well as environmental factors. These latter factors concern mainly feeding practices and are generally the most important because their variability is greater than that of the genetic factors. Many interrelations can exist between environmental factors and so when only one factor is considered this can lead to false conditions. For example, the calving period of the cow is not an important direct factor of variation in the annual milk protein content ; it represents rather a general indicator of herd management, which regroups, depending on the farm type, different factors. It is also possible that factors other than those experimentaly identified may affect protein content variations.