Abstract
Effect of lysine or lysine plus threonine supplement to the rice diet (protein level of 6%) for weanling and also adult rats was investigated. The rice diet I was consisting of 88.9% rice, 5% corn oil, 4% salt mixture, 2% vitamin mixture and 0.1% choline solution. Diet II was composed of the diet I plus 0.24% L-lysine-HCl. Diet III was composed of the diet II plus 0.12% L-threonine. Glutamic acid was added to the diet I and II to make isonitrogeneous with the diet III.
For the long term feeding test, initial body weight averaged 67g of male rats, Donryu strain, were fed ad libitum with the diet I, II and III for 32 weeks. PER was calculated individually from the body weight gain and the food intake for each period of [I] (1st-21st day), [II] (21st-42nd day), [III] (42nd-63rd day), [IV] (63rd-87th day), [V] (87th-105th day), [VI] (105th-126th day), and [VII] (126th-224th day).
The supplemental effect of lysine and lysine plus threonine was significantly observed by the period of II, at the age of the 9th week. The effect of only lysine to the rice diet was significantly observed after the age of the 9th week to the 15th week, but no further improvement of the body weight gain and PER in the group fed the diet III was observed. The plasma free valine, methionine, isoleucine, leucine and tyrosine were highest in the group III, following those in the group II, which were also higher than those in the rice group I, at the age of the 15th week (half the rats were killed and the rest of them was continualusly fed). On the contrary the plasma taurine value was highest in the rice group among the three groups. The taurine value in the rice plus lysine group was also significantly higher than that in the rice plus lysine and threonine group. It seems possible from the difference of the plasma amino acid values that there are still some reflection of improvement in the amino acids supplementation to the rice diet fed by the age of the 15th week.
In the short term experiment of the feeding test with adult rats, initial body weight of 198g for 25 days, the body weight gain and PER in the group II and III were almost the same and improved significantly from those of the rice group I.
