2005 Annual Report 4d.Progress report. This report serves to document research conducted under a Trust Agreement with Nestle USA entitled "The effect of dietary probiotics on the immmune response of neonatal pigs." Additional details of research can be found in the report for the parent project entitled "The Effect of Dietary probiotics on Immune and Gastrointestinal Function” 1235-52000-054-00D). The research objective was to test the effect of Bifidobacterium lactis (BB12) on the development of immune function in neonatal pigs. The presence of BB12 was evaluated in five sows and their litters. Three sows were orally treated with a daily dose of 20 billion colony forming units(cfu)/day of BB12 during the last trimester of pregnancy, and two other sows were treated similarly with the same amount of a placebo that contained the vehicle used in the probiotic preparation. Piglets within each litter were randomly divided into two groups at birth. Half of the litter was treated orally with 10 billion cfu of BB12 and the other half with an equal amount of placebo. Tissue samples from intestine (jejunum, ileum, cecum, proximal and distal colon, and Peyer's Patches), lymph nodes, spleen, liver and thymus were collected and analyzed from each pig. Quantitative cytokine mRNA expression levels for 46 genes were assessed using Real time Polymerase chain reaction (PCR). The presence of BB12 in the intestinal lumen was also tracked by Real time PCR. There is an up regulation of early innate immune response genes in neonatal pig treated with BB12, and this response is enhanced in BB12-treated pigs from BB12-treated sows. This is a proof of principle experiment to show that pigs can respond to human-derived probiotics that increase the activity of the mucosal immune system.