Influence of farming and feeding systems on composition and quality of goat and sheep milk

This paper deals with the effects of fanning systems linked to feeding aspects on the composition and quality of ewe and goat milk. When systems based on grazing and indoor systems are compared, the milk components (fat, protein, lactose) appear to be rather less influenced by type of farming system than by level of milk production. Significant differences are observed when ingested energy varies between pasture and indoor systems. Milk production depends on level of intake, and fat content on the indirect effect of dilution, while protein content varies generally like milk production. Goat milk production and its fat content can rise when grass is at an early growth stage. As in cows, fresh grass strongly influences the fatty acid contents of milk by increasing PUFA and CLA percentages. On cultivated pasture, the kind of fodder species, vegetation stage, season, and stocking rate can modify milk composition and quality. Natural pasture based farming systems produce milk rich in fat and in micro-components, which are beneficial to human health (fatty acids, vitamins), and in volatile components (flavour, terpenes). When three feeding systems based on natural pasture in the plain, on hills and on mountains are compared for goats, milk yield is slightly lower on mountain pasture but fat and protein contents and percentages of PUFA are higher, and the terpenes are more numerous in goat milk. Grass of natural pasture at an early stage produces milk richer in CLA. Supply of concentrates up to 0.6 kg/day/goat grazing natural pasture does not seem to modify the contents of volatile compounds, terpenes and flavour in milk, but it should reduce retinol content. In intensive indoor systems, a high level of intake due to fodders of good nutritive value or to high supplies of concentrates enables production of milk rich in protein and relatively low in fat. The ratio of fat to protein percentages can be reversed particularly in mid-lactation, when goats are fed diets short of fibre or fat. Consequently, the quality of cheese (granular paste, lack of nice goat taste) is lowered. When supply of concentrates in diets increases to 60% of total dry matter intake, fat content may decrease slowly and linearly, but if concentrate intake reaches 60-80%, fat content may decrease rapidly due to an increasing shortage of fibrosity in the ration. Studies confirm that the milk fat content influences cheese fat content as well as theological and sensorial qualities. Thus, this is an important factor, which has direct repercussion on cheese quality such as is appreciated by consumers. In the future, the farmer must select farming or feeding systems in accordance with trade conditions, consumers' demand and socio-economic conditions. If commercialisation of high quality cheeses is possible, farmers will have to define systems, that allow to optimise parameters of quality, even by limiting milk production. In the future, the fanners have to find a balance between the level of intensification and the quality of dairy products. (c) 2006 Elsevier B.V. All rights reserved.