Rangel-Lugo M, Su C L, Austic R E
Department of Animal Science, Cornell University, Ithaca, New York 14853.
Poult Sci. 1994 May;73(5):670-81. doi: 10.3382/ps.0730670.
Three experiments were conducted to determine the effect of excess dietary protein on threonine requirement of broiler chicks to 14 d of age (Experiments 1 and 2) and to determine the threonine requirement from 16 to 28 d of age (Experiment 3). Two dietary protein levels were used in Experiments 1 and 2:20% CP in a threonine-limiting basal diet containing wheat, peanut meal, and selected amino acids and 25% CP in the same basal diet supplemented with a mixture of amino acids lacking threonine. A threonine-limiting 25% CP diet based on corn, soybean meal, and amino acids was also included in Experiment 2. The threonine requirement of chicks from 16 to 28 d of age was determined using a single CP level (20%) in Experiment 3. Threonine requirements were estimated by broken line regression analysis of weight gain and feed efficiency. Threonine requirements based on weight gain were 7.7 and 6.7 g/kg of diet in Experiments 1 and 2, respectively, for chicks receiving the 20% CP diets. The requirements increased to 8.6 and 8.2 g/kg, respectively, for chicks fed the 25% CP diets based on wheat, peanut meal, and amino acids. The requirement for maximum weight gain of chicks fed 25% CP based on corn, soybean meal, and amino acids was 7.7 g/kg of diet. However, chicks ate more of this diet, and on an intake basis, the requirement of the chicks fed the 25% CP diets based on wheat and peanut meal or corn and soybean meal did not differ. Requirements based on feed efficiency were equal to, or less than, those based on weight gain in Experiments 1 and 2. Body moisture and fat contents were affected by dietary CP level (P < .01), ingredient composition (P < .01), and threonine content (P < .05). Estimates of threonine requirements based on regression analysis of plasma threonine concentrations were higher than those based on weight gain or feed efficiency. The threonine requirements of chicks fed a 20% CP diet from 16 to 28 d of age were 6.3 and 6.9 g/kg of diet based on weight gain and feed efficiency, respectively.
进行了三项试验，以确定过量日粮蛋白质对14日龄肉仔鸡苏氨酸需要量的影响（试验1和试验2），并确定16至28日龄肉仔鸡的苏氨酸需要量（试验3）。试验1和试验2采用了两种日粮蛋白质水平：一种是含小麦、花生粕和选定氨基酸的苏氨酸限制型基础日粮，粗蛋白含量为20%；另一种是在相同基础日粮中添加不含苏氨酸的氨基酸混合物，粗蛋白含量为25%。试验2还包括一种基于玉米、豆粕和氨基酸的25%粗蛋白苏氨酸限制型日粮。试验3采用单一粗蛋白水平（20%）来确定16至28日龄肉仔鸡的苏氨酸需要量。通过对体重增加和饲料效率进行折线回归分析来估计苏氨酸需要量。对于采食20%粗蛋白日粮的肉仔鸡，试验1和试验2中基于体重增加的苏氨酸需要量分别为7.7和6.7 g/kg日粮。对于采食基于小麦、花生粕和氨基酸的25%粗蛋白日粮的肉仔鸡，苏氨酸需要量分别增加到8.6和8.2 g/kg日粮。对于采食基于玉米、豆粕和氨基酸的25%粗蛋白日粮的肉仔鸡，最大体重增加时的苏氨酸需要量为7.7 g/kg日粮。然而，肉仔鸡采食这种日粮较多，按摄入量计算，采食基于小麦和花生粕或玉米和豆粕的25%粗蛋白日粮的肉仔鸡的需要量没有差异。试验1和试验2中，基于饲料效率的需要量等于或低于基于体重增加的需要量。胴体水分和脂肪含量受日粮粗蛋白水平（P<0.01）、原料组成（P<0.01）和苏氨酸含量（P<0.05）的影响。基于血浆苏氨酸浓度回归分析的苏氨酸需要量估计值高于基于体重增加或饲料效率的估计值。对于16至28日龄采食20%粗蛋白日粮的肉仔鸡，基于体重增加和饲料效率的苏氨酸需要量分别为6.3和6.9 g/kg日粮。
