AbstractWool‐biting behavior in housed sheep is a serious animal welfare problem and is difficult to control. Since we have found that sheep fed on rolled hay performed less post‐feeding wool‐biting than those fed on baled hay, here we mixed these two kinds of hay in four different proportions (0%, 33%, 67% and 100% of rolled hay) to test the effect of rolled hay on repressing wool‐biting behavior. We also measured the pulling force needed to remove a piece of rolled hay, baled hay, wool and fresh grass. Wool‐biting occurred most frequently in the treatment containing 0% rolled hay; however, there was no significant difference between the other three treatments. The pulling force needed to remove a piece of baled hay was significantly weaker than that for the other three objects; no other significant differences in pulling force were found. Our results suggest that the wool‐biting behavior of sheep was due to feeding frustration, which arises when they lack the appropriate oral stimulation from performing their normal foraging movement; this then redirects to the wool on their pen‐mates. Feeding sheep rolled hay, even in low quantities, can provide them with appropriate oral stimulation and was effective in repressing wool‐biting behavior.