Effects of Nutrition on Ewes’ Milk Quality

Control of milk composition is of importance in dairy ewes because milk is mostly used for cheese making. Besides numerous factors that alter milk composition, knowledge on the effects of nutrition is useful for it concerns both yield and milk content. Furthermore, modification of nutrition is a powerful and short-term means of altering milk composition. Global effects of nutrition are to be separated from specific effects of some nutrients, for they may be combined in order to finely control milk composition. Level of nutrition is a main factor affecting milk yield and milk composition in dairy ruminants : i.e. milk yield increases with level of nutrition and vice versa, but effects on milk composition are less clear. Milk fat content is in general negatively correlated to energy balance, whereas with protein content the correlation is positive. In consequence, in most cases, a high level of nutrition in dairy sheep will depress fat content and slightly increase milk protein content. On the other hand, an increase in dietary protein supply will increase milk protein yield, if the ewe has not reached its potential yield, but this response is not associated to changes in milk protein content. An easy means of increasing energy supply is to use high quantities of concentrate. As a result of rumen acidosis, this may directly depress milk fat and protein content and secondarily change energy partitioning from milk to body fat depots. The use of specific nutrients such as protected fat, or amino acids appears to be of interest as a mean of improving milk fat and/or protein content in dairy ewes. Limited experience is, however available, nowadays and advantages or drawbacks are not fully known.