초록
Two experiments were conducted to subdivide isoleucine (exp. 1) and valine (exp. 2) requirements for maintenance from the requirements for growth of broilers aged 1 to 3 weeks. Purified diets were used, containing five graded levels of isoleucine and valine. Based on weight gain response, the isoleucine requirement for growth was 7.50 mg/g weight gain and the daily isoleucine need for maintenance (mg) was 0.044 per unit metabolic body size ($(Wg^{0.75})$). Based on the N gain response, the isoleucine requirement for growth was 0.317 mg/mg N gain and the daily isoleucine need for maintenance (mg) was 0.040 per unit metabolic body size $(Wg^{0.75})$. Based on weight gain and N gain response, the total isoleucine requirement was calculated 244 mg/day or 0.59% of the diet, 274 mg/day or 0.66% of the diet, respectively. From the relationship of weight gain and N gain, 5.07% of the retained protein was comprised of isoleucine; the reported isoleucine content of chick muscle was 4.42%. The valine requirement for growth was 9.84 mg/g weight gain and 0.36 mg/mg N gain whereas the maintenance requirement was 0.046 or 0.052 mg per unit of metabolic body size (Wgo.11. According to the model developed to estimate valine requirement, the total requirement was 319 mg/day or 0.77% of the diet, 315 mg/day or 0.76% of the diet, respectively. Previous reported valine requirements for growing chicks of 7~24 days old were in close agreement with these estimates. As a percentage of retained protein, valine was calculated to be 5.81% ; the reported valine concentration of crude protein of chicks' body including feathers was 6.72%.