**5. Effects of EOs on milk fatty acids profile**

Milk fat content and FA composition are primarily determined by lipid metabolism in the rumen and the mammary gland [39]. EO supplementation can reduce the levels of C8 and C12 fatty acids. This occurs because EOs can produce potent inhibitors that hinder the synthesis of de novo FA in the mammary gland [40, 41].

The rate and extent of FA biohydrogenation could also impact variations among animal species [42]. In small ruminants, supplementation of EOs is more effective in the biohydrogenation process. For instance, Juniper EO addition enhanced the presence of n-3 fatty acid in goat milk, while anise, clove, and juniper had minimal impact on milk components [43]. Cinnamon oil elevated the concentration of unsaturated FA, n3 linolenic acid, and conjugated linoleic acid [44]. The inclusion of garlic or juniper EO in the diet of dairy cows resulted in an increased proportion of conjugated linoleic acid in milk [45]. Clove and thyme EO were found to be more effective in decreasing the biohydrogenation process and increasing the concentration of C18:3 n-3, C18:4 n-3, and n-3 FA in milk fat and decreased the concentrations of C18:3 n-6, C20:4 n-6, and n-6 FA in the milk of lactating goats [6].

Dairy cattle fed a blend of EOs (capsaicin, carvacrol, cinnamaldehyde, and eugenol) secreted more CLA, suggesting that EO influenced the ruminal biohydrogenation of PUFA [46]. Supplementation with 750 mg of a mixture of EOs had no change in milk FA profile [47]. However, supplementing 2 g/d of the same mixture increased the concentration of CLA in milk fat [48].
