The present study investigated the effects of fermented potato protein (FPP, Lianol® ferity) during gestation and lactation on productivity of sows. A total of 50 crossbred sows (Landrace×Yorkshire) in their 3 to 5 parities were allotted to one of two treatments (n=25) including control and FPP groups. FPP tablets applied in sows in two stages. Stage one involved applying FPP daily from 3 days before farrowing to 2 days after for 5 consecutive days. The second stage also involved a 5 day period around weaning time from 3 days before to 2 days after. After farrowing, the amount of feed offered 3 times per day gradually increased from about 3.6 kg at farrowing to 8.4 kg at late lactation. During the first lactation FPP tended to increase backfat thickness (BFT) at weaning at the first (p=0.069) whereas FPP increased BFT (p<0.05) at weaning in the second lactation. There was no significant effect of FPP on body weight changes and daily feed intake of sows. Decreased weaning to estrus interval was associated with applying lianol tablet at the second lactation (p<0.05). Weight of born alive piglets, weaned piglets and total weight gain were greater in FPP group at the second lactation (p<0.05). Applying FPP tended (p=0.062) to increase insulin like growth factor-Ⅰ(IGF-I) at the weaning time in the first lactation. The effect of FPP on IGF-I was significant at the second lactation, revealing a higher concentration in blood at post farrowing and weaning time (p<0.05). This study shows the benefit of using FPP tablets in sows to increase blood IGF-I and both initial and final litter size to improve piglet weaning weights.