# Utilization of Wool Integral Lipids to Determine Milk Fat Content in Suffolk Down Ewes
## 4 Discussion  
In the present study, wool FAs from Suffolk Down ewes at two time points during lactation (30 and 60 days) were characterized. Wool is a multicomponent fiber consisting of about 97% proteins, 2% lipids, and 1% mineral salts, nucleic acids, and carbohydrates [24]. Internal wool lipids are believed to account for the majority of the lipid content (1.2 to 1.5%) [22]. In our study, the wool fat content varied between 1.12% at 30 days to 1.08-1.25% at 60 days. [PERSON] et al. [14] reported that the total fat content of the hair from cows during early lactation ranged between 0.40% and 1.64%. Thus, the wool fat content reported in this study is similar to that obtained from the hair of cows. In ewes, the wool FAs are mainly composed of SFAs, as in the case of ewe milk samples, with minor proportions of MUFAs and PUFAs [25]. According to the literature [24], the main FAs in wool lipids are C16:0, C18:0, and C18:1n9c, and we identified many of the same FAs in our study. These FAs also were found to be the major FAs in the milk samples and together represented 71.3% of the total milk FAs [26]. In addition, we detected a small amount of FAs with chain lengths in the range of 12-26 carbon atoms. Furthermore, other FAs with odd numbers of carbon atoms were found in the wool lipids of Suffolk Down ewes. The FA C15:0 increased in wool FAs at 30 days in milk with low fat content, and no significant differences were detected in the period of 60 days (\(p>0.05\)). No significant differences were observed in the C17:0 concentration for each time of classification. [PERSON] [27] reported that ruminant fat contains certain FAs with an odd number of carbon atoms, such as C15:0 and C17:0, which are synthetized by the bacterial flora in the rumen. According to [PERSON] et al. [28], these FAs might provide information concerning the cows' glucose status, as they are synthetized de novo from propionyl-CoA by rumen bacteria or in the mammary gland. In wool, exogenous dietary essential FAs were also detected, such as C18:2n6c and C18:3n3, which are not synthetized by ruminant tissue, and their concentration is dependent on the quantity that flows out to the rumen [5]. These FAs were also detected in cattle hair and result from the direct uptake of FAs from the gut, which are delivered to the organs via blood [14]. A higher content of PUFAs, especially C18:3n3, was reported in milk fat from non-dairy sheep during grazing [6]. This is likely due to the higher concentration of C18:3n3 and C18:2n6c FAs in the pasture. In our study, we determined that the concentration of C18:3n3 was 1.33 mg/g DM and 0.44 mg/g DM in July and August, respectively, and the concentration of C18:2n6c was 0.23 mg/g DM and 0.07 mg/g DM in July and August (Table 1), respectively, which represent the major FAs found in the pasture. Significant differences in the wool FA composition were observed according to the classification of ewe milk with high and low milk fat contents for the two time points (30 and 60). The FAs C14:0, C20:3n6, and C24:0 increased in concentration in the early period, as demonstrated by the high milk fat content, but did not exhibit differences when collected at 60 days in the subsequent period. By contrast, the high concentration of the FAs C18:1n9c, C18:2n6c, and C22:2 was maintained over the two time points (30 and 60 days). In this sense, it is important to note that 30 days represented the point of peak milk yield in ewes [26,29], and, consequently, changes occurred in the pathways involved in FA production. In early lactation, the majority of dairy ruminants are confronted with a negative energy balance, for