Pairs of littermate, primiparous sows were fed a low folic acid, basal diet for 98 days to minimize body folic acid (FA) stores. Following the depletion period, sows were synchronized and bred via artificial insemination. Feeding of experimental diets was initiated on day 1 post-breeding and was continued throughout pregnancy. Experimental diets consisted of the low folic acid, basal diet supplemented with either 0 or 8 mg of FA per sow per day. The FA supplementation elevated sow serum FA concentration during pregnancy but did not alter immunoglobulin concentration in sow serum, piglet serum nor sow colostral whey at parturition. The FA supplementation did not affect the number of pigs per litter nor litter birth weight. The FA supplementation of the gravid sow did not alter piglet thymus or spleen weight, DNA, or protein content at birth, but resulted in a lower (P