Response to, and recovery from, an intramammary inflammatory challenge in dairy ewes: Effect of replacing dietary n-6 polyunsaturated fatty acids with n-3 polyunsaturated fatty acids.

Inflammatory processes, such as mastitis, are well known to impair not only health, but also productivity, underscoring the key role of the immune response in supporting sustainable livestock systems. Among dietary compounds with immunomodulatory properties, PUFA are of particular interest, as n-6 PUFA are generally associated with proinflammatory effects and n-3 PUFA with anti-inflammatory effects. This study evaluated whether the dietary incorporation of a source of n-3 PUFA (i.e., linseed oil) as a substitute for an n-6 PUFA source (i.e., soybean oil) could modulate the response of lactating sheep to an inflammatory challenge of the mammary gland. To meet this aim, 22 lactating Assaf ewes were allocated to 2 dietary treatments consisting of a TMR supplemented with either 2% DM of soybean oil or 2% DM of linseed oil. After an adaptation period to the diets (prechallenge), the sheep were challenged with an intramammary infusion of Escherichia coli LPS (10 µg per udder half), used as an experimental model of mastitis, and the response, subsequent recovery, and stabilization were characterized over the following 3-wk period (postchallenge). Feed intake, milk yield and composition, SCC, and blood hematological and biochemical variables were monitored before and after the LPS challenge to study their temporal dynamics. Substituting soybean oil with linseed oil had very limited effects, with only minor differences detected in DMI and lactate dehydrogenase. In both diets, milk yield and composition, SCC, and most blood variables showed similar patterns of variation, which were primarily driven by the LPS infusion. The temporal changes induced by the inflammatory challenge included significant decreases in DMI and immune cell counts and increases in SCC. However, during the postchallenge, most variables returned to prechallenge values rapidly, consistent with the mild nature of the inflammation. Overall, these results failed to support the hypothesis that replacing soybean oil, rich in n-6 PUFA, with linseed oil, rich in n-3 PUFA, in the diet of dairy ewes would modulate the response to and the recovery from an acute but mild intramammary inflammatory challenge.