This study was designed to examine the incorporation of omega-3 (n-3) fatty acids into the immune tissues of pigs nursing fish oil-fed sows and to determine the effect of maternal dietary n-3 consumption on in vitro immune cell eicosanoid production. On day 107 of gestation, 12 sows were randomly allotted to a diet containing either 7% menhaden fish oil (MFO) or lard (LRD). The fatty acid profile of serum, liver, thymus, splenocytes and alveolar macrophages (AM) of 18-21-day-old pigs was significantly affected by the fat source provided to the sow. Arachidonic acid (20:4n-6) content was typically reduced by more than 50% in MFO as compared with LRD pigs. In MFO pigs, eicosapentaenoic acid (20:5n-3) was the major n-3 polyunsaturated fatty acid, and its levels matched or exceeded those of arachidonic acid. Basal release of prostaglandin E, thromboxane B and leukotriene B by AM was 60-70% lower in MFO vs. LRD pigs. However, when these immune cells were stimulated with calcium ionophore A23187, release of leukotriene B was similar in MFO and LRD pigs. In conclusion, substituting MFO for LRD in a sow's late-gestation and lactation diet greatly elevated the content of n-3 fatty acids in the nursing pig immune cells and generally reduced in vitro eicosanoid release by pig immune cells.