Production et composition du lait de brebis : Effets de l'alimentation

Control of milk composition is of importance in dairyewes because milk is mainly used for cheese making.Besides numerous factors that alter milk composition,knowledge on the effects of nutrition is useful for itconcerns both yield and milk content. Level of nutritionis a main factor affecting milk yield and milk composition in dairy ruminants : i.e. milk yield increases withlevel of nutrition and vice versa, but effects on milkcomposition are less clear. Milk fat content is in general negatively correlated to energy balance, whereaswith protein content the correlation is positive. Inconsequence, in most cases, a high level of nutrition indairy sheep will depress fat content and slightly increase milk protein content. In addition, an increase in dietary protein supply will increase milk protein yield, ifthe ewe has not reached its potential yield, but this response is not associated to changes in milk proteincontent. An easy mean of increasing energy supply is touse 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 oramino acids appears to be of interest as a mean ofimproving milk fat and/or protein content in dairyewes. Limited experience is, however available, nowadays and advantages or drawbacks are not fully known.In the practical conditions of dairy flock managementthe effects of nutrition are often hidden in the complexity of numerous factors that are also known to alter milkcomposition. Therefore, as within-group individual nutritional status is unknown, global response in term of bulkmilk composition is difficult to predict. This leads to thenotion of group-feeding strategies that include the variety of animal responses to feeding treatments.