Bedö S
Arch Tierernahr. 1980 Aug;30(7-8):633-54. doi: 10.1080/17450398009425650.
Experiments concerning the nitrogen metabolism of 3-, 5-, 7-, 9-, and 11-week-old calves were carried through. The calves were daily fed 146, 219, 323 g milk replacer and differing amounts of dried skim milk (697, 761, 717, 723, 653 g). Energy consumption was dependent on the consumption of milk replacer. With increasing age, N-digestibility and N-retention from the feedstuffs diminished gradually. The smallest decrease of N-retention was observed with those animals receiving the highest amount of milk fat energy. The decrease of nitrogen digestibility can be attributed to the higher consumption of plant feedstuffs and the decrease of the biologic value of the protein. The experiments concerning the nitrogen metabolism show that a higher dosage of fat had a favourable influence on nitrogen retention. At an age of between 7 and 9 weeks correlation coefficients of between +0.50 and +0.36 were ascertained between the fat content of the feed ration and nitrogen retention. At the same age correlation coefficients of +0.60 resp. +0.53 were ascertained between the energy content of the ration and nitrogen retention. These investigations are the basis for the statement that for the nitrogen retention of calves at the age of 7 to 9 weeks feed energy (fat) is the most important factor. A close positive correlation could be observed between the crude protein consumed with the feed ration and the amount of digested nitrogen. Moderately positive correlation coefficients were calculated between the amount of nitrogen taken in resp. the amount of digestible nitrogen and the assessed amount of nitrogen at the age of 7, 9 and 11 weeks. The experiments with the nitrogen metabolism are the basis for the statement that protein and fat together determine the amount of nitrogen retention for calves fed wth moderate milk protein. For calves fed with less milk protein, 23 to 34% fat in the dry matter of the milk replacer proved to be successful. The favourable effect of a higher amount of milk replacer on nitrogen retention can also be attributed to the higher amount of chemotherapeutic sustances (vitamins, antibiotics) taken in with the milk replacer.
对3周龄、5周龄、7周龄、9周龄和11周龄犊牛的氮代谢进行了实验。每天给犊牛喂食146、219、323克代乳粉以及不同量的脱脂奶粉（697、761、717、723、653克）。能量消耗取决于代乳粉的摄入量。随着年龄的增长，饲料中氮的消化率和氮保留量逐渐降低。在摄入乳脂肪能量最高的那些动物中，观察到氮保留量的下降最小。氮消化率的下降可归因于植物性饲料摄入量的增加以及蛋白质生物学价值的降低。氮代谢实验表明，较高剂量的脂肪对氮保留有有利影响。在7至9周龄时，日粮脂肪含量与氮保留之间的相关系数在+0.50至+0.36之间。在相同年龄，日粮能量含量与氮保留之间的相关系数分别为+0.60和+0.53。这些研究是以下观点的依据：对于7至9周龄的犊牛，饲料能量（脂肪）是氮保留的最重要因素。日粮中消耗的粗蛋白与消化氮量之间可观察到密切的正相关。在7周龄、9周龄和11周龄时，摄入的氮量或可消化氮量与评估的氮量之间计算出适度的正相关系数。氮代谢实验是以下观点的依据：蛋白质和脂肪共同决定了中等乳蛋白喂养的犊牛的氮保留量。对于乳蛋白含量较低的犊牛，代乳粉干物质中23%至34%的脂肪被证明是成功的。较高量的代乳粉对氮保留的有利影响也可归因于代乳粉中摄入的化学治疗物质（维生素、抗生素）量较高。
