## 1 Introduction  
Over the past few years, the demand by the consumers for organically produced food has been increasing. This growth can be attributed to two major factors: health aspects for the consumers and environmental concerns [1, 2]. In addition, there are ethical issues considering that organic farming, based on the physical welfare of animals, using only organic feed, minimizes possible use of chemically synthesized allopachic medicinal products, promotes the biodiversity, protects the environment, is contrary to the genetic modification, and is distinguished for its high quality and the safety of products [3, 4]. Recently, after relevant research, the scientific community has become interested in milk fat, as it has been proven to contain ingredients such as conjugated linoleic acid (CLA), unsaturated fatty acids, and polyunsaturated fatty acids (PUFA), especially those of the n-3 group, which have beneficial effects on human health, on the cardiovascular system and in prevention of cancer [5]. Linoleic acid (LA) and \(\alpha\)-linolenic acid (ALA) are essential fatty acids, as they cannot be synthesized by the human body [6], and they are the major n-6 and n-3 fatty acids in milk. Moreover, numerous biological effects have been reported for CLAs, and several studies indicate that ALA has cardioprotective effects [7]. Furthermore, fat milk is a good source of fat-soluble nutritional vitamins, especially A (all-trans-retinol) and E (\(\alpha\)-tocopherol), which are known for their antioxidant activity [8; 9; 10; 11; 12]. The levels of the fat-soluble vitamins in milk are highly dependent on the type and the amount consumed in the feed. Higher concentrations of these vitamins are found in grass, legumes, and other green plants [13; 14]. Vitamin A and E concentrations of milk follow a seasonal trend with higher values to be achieved during the outdoor grazing period [15; 16; 17]. The species and animal breed are some of the main factors affecting the production of milk fatty acids [18; 19; 20; 21]. Furthermore, the levels of small- and medium-chain fatty acids are significantly higher in sheep and goat milk in relation to the cow [22]. Nutrition is one of the most important factors affecting the concentration of fatty acids in milk, and primarily that of the CLA, both in organic and conventional farms. [PERSON] and his associates [23] argued that composition of the milk and thereby its beneficial properties are largely determined by the food figure followed. Therefore, the effect of nutrition on milk components has been a subject of study for many researchers in various countries around the world [24; 25; 26; 27]. In Denmark for example, conventional farms, compared to organic ones, use different pasture [28], while in Sweden the same diet is followed by both farming systems [23]. Considered that nutrition largely affects the concentration and the profile of fatty acids in milk, the direct comparison of conventional and organic systems is not easy. So far, studies in Greece [29] report that even though a statistically significant difference is noted in the fat content of goat milk, with organic milk to show increased levels, this cannot be evaluated, as when confounders are tested, no differences are observed. The latter is attributed to the fact that organic and conventional goat farming in Greece do not have any substantial difference in terms of feeding strategies. The feeding system in Greece is based on seasonal natural grazing and on supplementary feeding of home-grown roughages and concentrates. Differences that have been previously identified between organic and conventional sheep and goat farms in Greece are related mostly to the use of antibiotics that are associated consequently with different microbiological profiles of the milk produced but not with the feeding strategies [30].