AbstractPens of pigs grown from 30 to 60 kg liveweight (LW) and 30 to 90 kg LW in separate experiments were fed diets containing either 75 or 150 kg t−1dietary dry matter of de‐oiled herring offal silage stored for up to 8 weeks, and their performance compared with pens of pigs fed control diets based on soya bean meal formulated to contain equivalent levels of total lysine. All pens of pigs were rationed on the same time‐based scale of feeding. Pigs in both weight ranges fed herring silage diets grew significantly faster than the control pigs; in the 30–60 kg LW range growth rates were 687 and 529 g day−1(P<0.01) and in the 30–90 kg LW range, 670 and 588 g day−1(P= 0.05), respectively. The mean feed: gain ratio was also better with pigs fed the herring silage diets. No significant differences were found between treatment and control pigs slaughtered at either 60 or 90 kg LW for back fat probe measurements or killingout percentage. No pigs were down graded by the Meat and Livestock Commission carcass quality c