Dietary clay (Calibrin-Z; CZ), has been shown to enhance weanling pig performance due to its barrier function in the intestine. An 18-mo trial was conducted to investigate the long-term feeding effects of CZ in swine. Sixteen crossbred sows (3.2 parities) were randomly assigned to 2 TRT. The sows were fed an antibiotic free diet with 0 (CON) or 0.1% CZ during the trial. The farrowings were between Nov 2012 and Mar 2013, and from Apr to Aug 2013. Litter size and weaning weights were recorded (sow was the experimental unit). Weaned pigs from approximately 1/2 of the litters (362 pigs) were divided into 2 TRT in a split-plot arrangement based on sow TRT, and fed diets with 0 or 0.1% CZ until slaughtered (litter was the experimental unit). Pigs were weighed and blood samples collected at weaning, d-60, 90, 140, and end of trial. Feeds were formulated to meet Japanese feeding standards for swine. Total born from the 2 farrowings was not different (P > 0.05) averaging 12.7 for the sows fed the CON vs. 14.4 piglets for the sows fed 0.1% CZ. However, total pigs born in the second litter was numerically higher (12.5 vs. 15.8; P > 0.05) when CZ was fed. This improvement in the size of the second litter suggests that feeding 0.1% CZ for a longer period may have positive effects on sow reproductive performance. The combined data of 2 cycles of G-F pig performance, showed pigs fed 0.1% CZ diets needed 4.9 fewer days to reach market weight (166.8 vs. 161.9 d; P < 0.01) although ADG was not improved (840 vs. 864 g; P > 0.05). Total feed consumption was lower in pigs fed the CZ diets (308.6 vs. 287.4 kg; P < 0.01), and therefore, an improvement of FCR (2.92 vs. 2.75; P < 0.05) was obtained when pigs consumed diets containing 0.1% CZ. There were no differences (P > 0.05) in the serum biochemical markers concentrations, such as total protein, albumin, GOT, GTP, γGTP and IgG etc. In conclusion, pigs fed commercial diets containing 0.1% Calibrin-Z under normal conditions in Japan may increase numbers of total born and born-alive, and improve FCR in growing-finishing phases.