Impact of Milk Thistle Cake as the Natural Antioxidant Source on the Mitigation of Oxidative Effects in Goat Milk Induced by Oxidized Linseed Oil

This study explores a novel feeding strategy in the nutrition of dairy goats, utilizing milk thistle cake supplements to mitigate milk oxidation determined by the presence of oxidized linseed oil in diets. An experimental trial involving 30 dairy goats was conducted with three groups: a control group fed a diet with 7% fresh linseed oil (CON), an experimental group fed a diet where the fresh linseed oil from the CON group was replaced with oxidized linseed oil (LOO), and an experimental group fed a diet with 7% oxidized linseed oil and 10% milk thistle cake (LOM). The milk thistle cake had a rich antioxidant composition (vitamin E, xanthophylls, and polyphenols) with potential beneficial effects on milk degradation parameters. The results showed that the LOM diet led to a decrease in milk casein content (<i>p</i> = 0.041) while positively influencing the concentration of iron (13.24 vs. 14.93 mg/kg). In terms of fatty acids, the results suggested that milk thistle cake can counteract the negative effects of the oxidized oil (increasing SFAs, decreasing PUFAs and MUFAs) by modulating the content and reducing its negative effects. Moreover, the LOM group positively influenced the milk antioxidant potential by increasing the levels of antioxidant compounds (vitamin E, <i>p</i> < 0.001; total polyphenols, <i>p</i> < 0.01; antioxidant capacity, <i>p</i> < 0.0001). Moreover, an improvement in the milk primary and secondary degradation parameters was observed, i.e., a significant decrease in the levels of conjugated dienes (<i>p</i> = 0.023) and p-anisidine (<i>p</i> < 0.0001). The study demonstrated the benefits of using milk thistle cake in goat nutrition as it helps reduce the oxidative effects induced by oxidized linseed oil on the nutritional quality of milk and its degradation.