Abstract: [Objective] To assess the impacts of feeding frequency on backfat thickness and reproductive performance in pregnant sows. [Method] A total of 480 multiparous Duroc sows were selected and randomly divided into two groups （T1 and T2） according to the principle of similar parity （2^nd -7^th） and backfat thickness （11-22 mm） before artificial insemination （AI）. T1 group sows （n=220） fed once per day, and the feeding time was 8:00. T2 group sows （n=260） fed twice per day, and the feeding time was 8:00 and 15:00, respectively, with half of the total amount of diet each time. Both groups fed the same amount each day. The experimental sows were housed in individual crates.[Result] ①Feeding frequency had no significant （P>0.05） effects on backfat thickness on 56^th day of gestation and the difference of backfat thickness between day of AI and 56^th day of gestation （backfat thickness on 56^th day of gestation minus that on day of AI） . A trend of increase in backfat thickness on 110^th day （P=0.06） of gestation and the difference of backfat thickness between 56^th day and 110^th day （P=0.09） of gestation （backfat thickness on 110^th day minus that on 56^th day of gestation） in T2 group was observed in comparison to T1 group. ② There were no significant （P>0.05） effects of feeding frequency on the total number of piglets per litter, number of live piglets, number of stillborn piglets, number of mummified fetus, litter weight at birth, and individual birth weight. ③ For the third-parity sows, backfat thickness on 110^th day （P=0.01） of gestation and the difference of backfat thickness between 56^th day and 110^th day （P=0.04） of gestation in T2 group was significantly higher than those in T1 group. For sows with five and above parities, an increasing trend in the difference of backfat thickness between 56^th day and 110^th day （P=0.08） of gestation in T2 group was also found in comparison to T1 group. ④ Feeding frequency had no significant （P>0.05） effects on second-parity sows in terms of total number of piglets per litter, number of stillborn piglets, number of mummified fetus, litter weight at birth, and individual birth weight, while second-parity sows in T2 group had higher number of live piglets than those in T1 group （P=0.07）. [Conclusion] Reducing feeding frequency from twice to once per day had no negative impacts on reproductive performance of sows.

Key words: feeding frequency, Duroc sows, backfat thickness, reproductive performance