# Utilization of Wool Integral Lipids to Determine Milk Fat Content in Suffolk Down Ewes
## 4 Discussion
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multicolumn{1}{c}{**Variable**} & \multicolumn{1}{c}{**True**} & \multicolumn{1}{c}{**False**} & \multicolumn{1}{c}{**False**} & \multicolumn{1}{c}{**True**} & \multirow{2}{*}{**MCC**} & \multirow{2}{*}{**Accuracy**} \\  & \multicolumn{1}{c}{**Positive**} & \multicolumn{1}{c}{**Positive**} & & & & & \\ \hline C18:1n9c & 9 & 3 & 2 & 10 & 0.58 & 79.17 \\ C18:2n6c & 8 & 4 & 3 & 9 & 0.41 & 70.83 \\ C22:2 & 8 & 5 & 3 & 8 & 0.34 & 66.67 \\ C18:1n9c + C18:2n6c & 10 & 2 & 1 & 11 & 0.75 & 87.50 \\ C18:1n9c + C22:2 & 9 & 5 & 2 & 8 & 0.43 & 70.83 \\ C18:1n9c + C18:2n6c + C22:2 & 10 & 2 & 1 & 11 & 0.75 & 87.50 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Discriminant analysis of wool fatty acids and milk fat content, to determine the best classification of ewes with high milk fat content. three reasons: the increased demands of calving, decreased dry matter intake shortly before and after calving, and the lagging dry matter intake compared with the energy demands of milk production [28; 30]. This probably occurred in these animals, as suggested by the marked body weight losses [5]. Thus, long-chain FAs from body fat mobilization would be expected to be incorporated into wool FA, especially C18:1n9c. This can be seen by the higher concentration of long-chain FAs in the wool in this period. Moreover, at 60 days, in contrast to at 30 days, wool from ewes with high milk fat content had a high concentration of de novo synthesized FAs (C10:0 to C16:0). This can be principally explained by the fact that de novo synthesis is reduced when ruminants rapidly mobilize body fat. Wool FAs can originate from four major pathways: directly from the diet, de novo synthesis, formation in the rumen, and released from body fat stores [31]. Among the volatile FAs (VFA), acetate (60-70% of all VFAs) and the butyrate-derived \(\beta\)-hydroxybutyrate (BHBA) are the main precursors for the de novo synthesis of FAs in peripheral tissues (70-80% of acetyl groups for lipogenesis in adipose tissue, 15-30% in intramuscular depots, and the principal precursor in the mammary gland of the synthesis de novo of FAs) [25]. De novo is the pathway for the C4:0 to C14:0 acids, together with about half of the C16:0 from acetate and BHBA. The other half of the C16:0 acid is partly derived from plasma, from dietary lipids, and from the lipolysis of adipose tissue triacylglycerlycerols, such as FAs with chain lengths of 18 or more carbon atoms [27; 32]. In cows, low FA concentrations, in a range from C4:0 to C14:0, were reported in the period of early lactation, compared with the mid-lactation period, due to inhibition of de novo synthesis by long-chain FAs from body fat mobilization [32; 33]. Only in periods characterized by a positive energy balance, when an excess of energy and acetyl-CoA are present, can malonyl-CoA be synthetized and de novo FA synthesis be performed, which can be detected throughout the body, including the hair [15]. However, high concentrations of C18:1n9c and other preformed FAs (C18:2n6c and C22:2) are maintained until 60 days in wool from ewes with high fat milk. [PERSON] et al. [34] reported that the preformed FA concentration, originating from adipose tissue mobilization, varied in early lactation, and remained constant through until week 16. The FAs C18:0 and C18:1n9c primarily account for this response in the wool. In this study, desaturase indexes (DI C14, DI C16, and DI C18) varied according to the classification period and milk fat content. Stearoyl-CoA desaturase (SCD) is the enzyme responsible for the conversion of C14:1, C16:1, and C18:1, which are produced from C14:0, C16:0, and C18:0, respectively [35]. Significant differences were only observed at 30 days in milk in wool fat (\(p<0.05\)) with a high DI C14 value in ewes' milk with low fat contents, as compared to milk ewes with high fat contents. Moreover, high values of DI C18 were found in wool from ewes with a high milk fat content (\(p<0.05\)).