###### Abstract  
The quality of milk is fundamental to producing safe milk and dairy products that are suitable for consumption. The objective of this study was to determine the influence that the content of dietary polyunsaturated fatty acids (PUFA) has on the total mixed ration (TMR) and lactation stage of milk's composition and the fatty acid profile (FA) of the dairy Najdi breed. During the lactation period, 48 Najdi ewes used the following four treatments: traditional feed (TR) and three total mixed ratios (TMR1, TMR2, and TMR3) with different PUFA content. Milk samples were taken from whole milk in the morning. The chemical composition and FA profile were analyzed. The results show that the ewes fed TMR1 with a PUFA content (25.20%) produced high-quality milk as they contained high levels of polyunsaturated fatty acids (PUSF), linoleic acid (LA), \(\alpha\)-lionic acid (ALA) and omega-3 (n3). On the other hand, the milk of ewes fed TMR2 with PUFA (15.06%) contained high levels of unsaturated fatty acids (USF) and monounsaturated fatty acids (MUFA) and had significantly reduced hypercholesterolemia (HFA). It can be concluded that milk fat, protein, and total solids in the milk of Najdi sheep increased as lactation progressed, while lactose remained constant. Furthermore, as lactation progressed, saturated fatty acids (SFA), stearic acids, and oleic acids (OA) increased while USF and MUFA decreased. TMR diets can directly benefit the producer and livestock by producing high-quality milk while reducing its economic value. TMR; unsaturated fatty acid feed; stage of lactation; milk quality; Najdi sheep +
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The addition of lipids with a high PUFA content from 2 to 5% in the diet of ruminants plays a crucial role as an energy source, reduces the risk of rumen acidosis, alters milk fatty acids, and reduces nutritional costs [7]. By contrast, the intake of large amounts of lipids in the diet of ruminants can influence the microbial population in the rumen and, thus, the fermentation parameters in the rumen and the digestion of feed components [8]. It has also been observed that adding fat to the diet reduces methane production [9]. Therefore, fermentation processes in the rumen are influenced by diet, especially oil supplementation, and the use of this strategy can improve milk quality [10]. Furthermore, [PERSON] et al. [11] mentioned that the rumen is considered the central axis for the control of PUFA components, especially conjugated linoleic acid (CLA), in milk and meat, as it is mainly responsible for converting feed nutrients into high-quality products. Several studies have examined the effect of adding unsaturated fats of plant origin in the diet of sheep on the fatty acid composition of milk fat [12; 13; 14]. However, they were unable to determine the connection between the fatty acids in milk and the consumption of feed. On the other hand, the amounts of unsaturated lipids supplied to dairy sheep to meet their requirements are around 60 to 165 g/day [14]. Dairy sheep products are subject to several factors that negatively impact their productivity, efficiency, sustainability, and product quality. The main factors that stand out include management strategies, the quality of diet, and the stage of lactation [15]. The important physiological factor is the stage of lactation, as milk properties in sheep improve as lactation progresses, and sheep reach their maximum production a few weeks after birth. In addition, the FA profile of fatty milk is influenced by the physiological state of the animal; e.g., long-chain fatty acids (LCFA) were higher in eve milk after lambing. As part of the negative energy balance (NEB), fatty acids were mobilized from the tissue and converted into milk fat [16]. Dairy fat and human health are related topics that are well-known to consumers.