Effects of nutrition on ewes’ milk quality

Abstract

Control of milk composition is of importance in dairy ewes because milk is mainly 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. 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. In addition, 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 mean of increasing energy supply is to use high quantities of concentrate, but this may directly depress milk fat and protein content and secondarily turn energy partition 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.

In the practical conditions of dairy flock management the effects of nutrition are often hidden in the complexity of numerous factors that are also known to alter milk composition. Therefore, as within-group individual nutritional status is unknown, global response in term of bulk milk composition is difficult to predict. This leads to the notion of group-feeding strategies that include the variety of animal responses to feeding treatments.