Effect of high protein diet with low lysine/protein ratio on growth performance, meat quality and sensory traits of pork in Duroc finishing pigs

The effects of a high crude protein (CP) and low lysine/CP ratio with a rice cake “mochi sweets” by-product based diet on the growth performance, carcass traits, meat quality, adipocyte size in intramuscular fat, and sensory traits of pork in Duroc finishing pigs were investigated. Fourteen pigs with an average body weight of 66.7±3.3 kg, were assigned to two groups by sex and body weight. There were 7 pigs per pen, 4 gilts and 3 barrows each. The first group which was fed a commercial diet, 15.4% CP and lysine/CP=0.045, served as the control. The other group was fed a diet with a high CP and low lysine/CP ratio. This diet had a 17.0% CP and a lysine/CP ratio=0.028. It was denoted as the AB (amino acid balance method) group. The pigs in both groups were fed until the required body weight was reached, which was approximately 116 kg. It was observed that the average daily gain was not significantly different between the groups. Additionally, the carcass traits, including the backfat thickness, carcass grading, and dressing percentage, were observed to be not significantly different between the groups. The intramuscular fat content of the Longissimus dorsi muscle (LM) in the AB group (6.22%) was higher than that of the control group (3.14%) (P <0.01). In the LM, L* was increased (P <0.05), “Tenderness” and “Toughness” as TENSIPRESSERsup(TM) measurements, of the AB group, were lower than that of the control group (P<0.01). Regarding the composition of fatty acids of the intramuscular and subcutaneous inner fat, dietary AB caused an increase in the C18 : 1 and monounsaturated fatty acids (MUFA) in comparison with the control group (P<0.05). The adipocyte size in the LM of the AB group was larger compared to the control group (P<0.05). In the sensory evaluation, variable such as the “Initial tenderness” of the AB group ranked higher than that of the control group (P<0.05). Meanwhile, the “Flavor intensity” and “Off-flavor” parameter of the AB group tended to be lower than that observed for the control group (P<0.10). In addition, the “Tenderness at mastication”, “Juiciness after chewing 10 times”, and “Sustained juiciness, until swallowing” were not affected by either treatment. In conclusion, an amino acid balanced diet could increase the intramuscular fat content, which is associated with an increase in the C18 : 1, MUFA, and adipocyte size. Additionally, the evaluated diet has an effect on the sensory traits of pork.