Abstract
Experiments were conducted to evaluate the nutritive values of supplemental L-lysine, liquid and powder type, and DL-methionine in weanling pigs. For feeding trial, 165 weanling pigs were treated in 2 controls; 18 and 16% CP, 6 supplementations of lysine alone to 16% CP diets; 0.1, 0.2 and 0.4% of liquid and powder type each, and 3 supplementations of lysine + methionine to 15% CP diets; 0.05 + 0.025, 0.1 + 0.05 and 0.2 + 0.1%. Pigs were fed for 5 week to investigate the protein sparing effect of supplemental amino acid, and the optimal supplemental level. A metabolic trial included the measurements of digestibilities of dry matter, crude protein, crude fat, crude fiber, energy, phosphorus and amino acids. The liver acinar cell culture was conducted for the protein synthesis activity of the pigs fed each experimental diet. Supplementation of both type of L-lysine in 16% CP diet showed improved daily weight gain and feed efficiency which were compatible with those of pigs fed 18% CP diet. Groups fed liquid lysine did not differ from those fed powder type in growth performance. Supplementation of lysine and methionine to 15% CP diet did not improve growth performance of pigs to the extent that 18% CP diet was fed. In nutrient digestibility, 16% CP control diet showed significantly (p < 0.05) lower crude protein digestibility than any other treatments. Digestibilities of 16% CP diets with lysine supplementation were equal to that of 18% CP control, while digestibilities of 15% CP diets with the supplementation of lysine + methionine was inferior to that of 18% CP control. Supplementation of lysine alone reduced the nitrogen excretion compared to the none supplemented control groups. However, addition of lysine + methionine excreted more nitrogen than controls. Pigs fed diet supplemented with lysine alone, or lysine + methionine excreted less fecal phosphorus than those fed none supplemetation. Retained protein from liver tissue of pigs fed 18% diet was significantly (p < 0.05) greater than those fed 16% CP diet. A significant difference (p < 0.05) was observed in physical type of lysine. Feeding of powder type showed less secreted protein and greater retained protein in the culture of liver acinar cell. It is concluded that supplementation of lysine at the level of 0.1 to 0.2% can spare 2% of dietary protein and reduce nitrogen excretion by 19.3%. Also, no difference in nutritional values was observed between liquid and powder lysine in weanling pigs.