Identification of the optimal monosodium glutamate–condensed molasses soluble inclusion level replacing molasses in growing-finishing pigs

This study aimed to evaluate the effects of replacing molasses with monosodium glutamate (MSG)-condensed molasses solubles (CMS) in growing-finishing pig diets and determining the optimal replacement ratio. Experiment 1, a total of 100 crossbred growing-finishing pigs [(Landrace × Yorkshire) × Duroc] (9 weeks of age; initial body weight 23.17 ± 3.51 kg) were randomly assigned to five dietary treatments for 14 weeks. Pigs were randomly assigned to five dietary treatments with 5 replicates of 10 pigs per pen. The treatments consisted of: (1) PC (basal diet with 2% molasses), (2) NC (basal diet), (3) T1 (basal diet with 1.5% molasses + 0.5% MSG-CMS), (4) T2 (basal diet with 1% molasses + 1% MSG-CMS), and (5) T3 (basal diet with 2% MSG-CMS). Growth performance, nutrient digestibility, blood profiles, fecal microbiota, and economic efficiency were assessed. Average daily gain in the T1 was higher (<italic>p</italic> < 0.05) than that in the T3. The average daily feed intake in the T3 was lower (<italic>p</italic> < 0.05) than that in the other groups. In contrast, T1 and T2 had higher (<italic>p</italic> < 0.05) average daily feed intake than other groups. Economically, the T1 showed higher total weight gain and lower (<italic>p</italic> < 0.05) feed cost per kg gain than the NC and T3 during the growing phase. Experiment 2, a total of 5 crossbred growing-finishing pigs (11 weeks of age; initial body weight 36.84 ± 0.51 kg) were used in a 5-week metabolism trial based on a 5 × 5 Latin square design to investigate the effects of MSG-CMS on nutrient digestibility and nitrogen retention. The T1 had higher (<italic>p</italic> < 0.05) gross energy digestibility than the T3. Fecal nitrogen retention was lower (<italic>p</italic> < 0.05) in the T1 and NC than in the T2, while the T2 had higher (<italic>p</italic> < 0.05) total nitrogen retention than the NC. In conclusion, Molasses can be replaced with MSG-CMS without negative effects, with 25% replacement being the most effective for improving growth performance, nutrient digestibility, and economic efficiency in growing-finishing pigs.