|Budget Amount *help
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1991 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1990 : ¥1,000,000 (Direct Cost : ¥1,000,000)
(1) As it had been proved prior to this study that lysine would be a sole and severe limiting amino acid in male Holstein calves less than 3 months of age (or less than 90 kg in body weight) when a diet consisted of rice straw, corn and corn gluten meal(CGM) was given, it was examined in 1990 and 1991 if the same state of affairs are applicable also to calves more than 3 months of age. (2) When the similar type of diet containing 13% CP was given calves weighing 90 kg initially at 3.0% body weight, the administration of lysine via the esophageal groove did not improve N-balance. On this occasion, the daily intake of CP was 3.9 g/kg, and the ratio of ruminally degradable protein(RDP) estimated according to NRC per metabolizable energy(ME) was 6.3 g/MJ. (3) Lysine was not limiting also when the similar type of diet with 15 % CP was given calves weighing 170 kg initially at 2.7 % body weight. On this occasion, the CP intake was 4.0 g/kg/d and the RDP/ME ratio was 5.5 g/MJ. (4) It was sugg
ested that the synthesis of rumen microbial protein(MCP) would be insufficient for the highest growth rate even in calves more than 3 months of age when they receive a low-CP or high-urea diet. (5) The administration of lysine via the esophageal groove improved significantly the N-balance when calves weighing 140 kg initially were given the corn and CGM diet containing 11% CP at 2.7 % body weight. On this occasion, the CP intake was 3.0 g/kg and the RDP/ME ratio was 4.7 g/MJ. (6) The ARC assume that the RDP/ME ratio of 7.8 g/MJ is required for the highest production of MCP, but the criterion was suggested to be too high to achieve when a diet consisted mainly of corn. (7) The RDP/ME ratio of 6.3 g/MJ was adequate for the highest MCP production when urea was added to corn-based diets as a main RDP source, and when the degradability of diets was estimated acoording to NRC. (8) Because the efficiency for the conversion of urea-N into microbial N was as low as 0.69, the RDP/ME ratio adequate for the highest MCP prpduction might be lower than 6.3 g/MJ, if ordinary RDP is utilized more efficiently by rumen microbes.