Efficacy of decreasing levels of tryptophan relative to lysine on the performance and meat quality of finishing pigs

We conducted this research to examine the reducing level of lysine : tryptophan ratios in the diet affected the performance and meat quality of finishing pigs.At the end of the experiment, 144 crossbred finishing pigs (Duroc × [Yorkshire × Landrace]) having an average body weight of 70.6 ± 3.9 kg were randomly assigned to four dietary treatments (9 replications, 4 pigs per pen).The pigs in the 4 treatments were fed diets with different lysine : tryptophan ratios, such as 1 : 0.175, 1 : 0.160, 1 : 0.145, and 1 : 0.130.In considering average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR), the ratio of tryptophan and lysine (Lys : Trp) did not show any significant effect (p > 0.05).Moreover, nutrient digestibility had no significant impact (p > 0.05).However, the decreasing level of tryptophan linearly decreased the back-fat thickness at overall period (p = 0.038) and reduced at week 5 (p = 0.007).Additionally, the lean meat percentage (LMP) showed a tendency to increase at initial (linear effect, p = 0.097) and increased at overall period (linear effect, p = 0.045).Therefore, we suggest that Lys : Trp ratio of 0.130 could enhance the meat quality in finishing pigs.