# Utilization of Wool Integral Lipids to Determine Milk Fat Content in Suffolk Down Ewes
## 1 Introduction  
Sheep farming is of vital importance to national economies, principally in the Mediterranean basin, particularly in France, Spain, Italy, and Greece [1]. In the Mediterranean and East European countries sheep milk is often produced by specialized dairy breeds, and sheep milk products are commercialized internationally. Consequently, due to the high quality of sheep milk products, more consumers are demanding dairy products with a special flavor associated with the territory where the animals live [2]. On the other hand, in South America, sheep milk production is traditionally performed by hand, and the raw milk is used directly, without the addition of dairy cultures, which gives these products their typical flavors and aromas [3]. In fact, an increase in cheese varieties from manufacturers using sheep milk has been observed in Chile; however, the production system varies according to the country; e.g., in Chile, sheep production is based largely on grazing systems, whereas in Spain, for example, sheep cheese is produced throughout the year, leading to intensification and the need for reproductive management [4]. This significant growth in sheep cheese production has stimulated research into sheep milk production with various breeds and production systems [5, 6]. Dairy milk products from sheep have acquired importance in the global market, due to their nutritional value and high quality [1]. The nutritional value of sheep milk ischaracterized by higher levels of total solids and major nutrients, compared with milk from other mammals; with lipids being the most important components of milk, in terms of cost, nutrition, and the physical and sensory characteristics that they impart to dairy products [7]. Most sheep milk produced throughout the world is transformed into cheese. Rarely is sheep milk directly consumed and, thus, the majority of efforts are focused on its transformation into high quality dairy products [8]. The nutritional value of products depends on the type of milk from which they are made, and in sheep cheese, the fat content is important, because fat defines the consistency, taste, aroma, and nutritional value of the resulting dairy product [9]. The fat concentration in milk can be altered by diet, and particularly by factors that affect rumen fermentation [2]. Thus, the nutritional value and sensory properties of milk are of great importance, and the determination of fat content during lactation is relevant in the manufacturing of dairy products [10]. Wool is important as a textile fiber and is increasing in popularity, despite the current restrictions on the use of agricultural by-products that classify wool as a waste product, with no economic incentives to valorize wool beyond disposal [11]. Wool, similarly to hair, is a metabolically inert and incremental tissue and can, thus, provide an archival record, e.g., of changes in diet, with the advantage that it can be noninvasively, collected and conveniently stored with little cost for long periods of time; thus, preserving this information for retrospective verification [12]. Moreover, researchers have found that it is possible to detect drug residues in hair long after treatment [13]. Hair has become an important focus in diverse fields of animal research, due to the information it can provide about an animals' environment [12; 13], and it reflects the metabolism of the proceeding 2 to 3 weeks [14]. Previous studies have established a relationship between the fatty acid profile of hair and energy availability in lactating cows, reproduction, and milk protein [14; 15]. However, no information exists about sheep wool fatty acids and their relationship with milk productive parameters. According to the present knowledge about hair, we expected that information about the chemical composition of sheep milk, specifically milk fat content, could be reflected in wool fatty acids. Thus, the aim of this study was to differentiate sheep's milk with high fat content at two time points during lactation (30 and 60 days) using wool fatty acids.