| Abstract : |
Isoleucine is a branched-chain essential amino acid in pig nutrition that regulates protein metabolism, fat deposition, and glucose utilisation, and serves as an energy substrate for immune protein synthesis, thereby enhancing immune function. It also improves growth performance, feed intake, and nutrient utilisation. However, the optimal standardized ileal digestible (SID) isoleucine:lysine ratio for young pigs remains controversial. This study aimed to determine the optimal SID isoleucine:lysine ratio for pigs weighing 7–30 kg. Four groups of piglets were fed diets with SID isoleucine:lysine ratios of <0.5, 0.5, 0.55, and 0.6. The results demonstrated that a ratio of 0.55 was optimal, increasing live weight at 70 days of age by 8.8% (p<0.05) without adverse physiological effects. This ratio reduced serum glucose, creatinine, urea, total cholesterol, low-density lipoprotein cholesterol, and triglycerides, while increasing total protein and high-density lipoprotein cholesterol and decreasing ALT and AST activity. A ratio of 0.5 was less effective but still increased live weight by 6.2% (p<0.05) and decreased serum glucose, creatinine, urea, and triglycerides, with a concomitant rise in total protein. In contrast, increasing the ratio to 0.6 did not improve body weight and altered protein and lipid metabolism, as evidenced by increased total protein and globulins, decreased albumins and albumin-to-globulin ratio, elevated cholesterol due to higher low-density lipoproteins, and reduced ALT and AST activity. |
