The present study consists of two experiments. In experiment 1, a total of 120 weaned piglets (Yorkshire × Landrace) (7.3 ± 1.9 kg) were allocated to five treatments, and four replications (pens) with six piglets/pen. In experiment 2, 40 male pigs (23.0 ± 2.2 kg) were allocated to five treatments and eight replications (individual pens). In both experiments, the control diet contained fish meal (FM) as the sole protein supplement (CPH0), while the experimental diets consisted of four different diets in which crude protein (CP) from FM in CPH0 was replaced by the CP from catfish (Pangasius hypophthalmus) by-product protein hydrolyzate (CPH) at four different levels: 100 % (CPH100), 75 % (CPH75), 50 % (CPH50) and 25 % (CPH25). The results in experiment 1 showed that the highest average daily gain  (ADG) over the 5-week period after weaning was recorded for piglets on CPH100 (307 g/day), and the lowest for piglets fed CPH0 (287 g/day) (P< 0.01). Feed conversion ratio (FCR) was lower in CPH100 (1.43 kg feed/ kg gain) than in CPH0 (1.51 kg feed/kg gain) (P