Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL.
Poult Sci. 2019 Apr 1;98(4):1723-1731. doi: 10.3382/ps/pey530.
Three slope-ratio precision-fed rooster assays were conducted wherein roosters were precision-fed 0, 5, 10, 15, or 20% (levels varied among experiments) refined soy oil, refined corn oil (RCO), poultry fat, crude soy oil, crude corn oil, palm oil, vegetable blend acid oil 1 and 2, soy acid oil, tallow, or choice white grease as part of a ground corn diet. Multiple regression slope-ratio analysis of nitrogen-corrected true metabolizable energy regressed on dietary fat level was used to estimate relative metabolizable energy (RME) values. The RME values were calculated as the regression coefficient of the test lipid divided by the regression coefficient of the reference refined soy oil or RCO (set at 100%). The results of the rooster experiments indicated that only the RME values of palm oil 1 (83%) and tallow (74%) were significantly lower (P < 0.05) than that of refined soy oil or RCO. It was observed that the differences among fat sources were often greater at the higher inclusion levels of 15 and 20%. In addition to the slope-ratio precision-fed rooster assays, a limit-fed broiler chicken growth assay was conducted. The broilers were limit-fed to 70% of their expected daily intake from 11 to 20 d of age, and four lipid sources (RCO, palm oil 2, choice white grease, and vegetable blend acid oil 2) were tested at 0, 5, and 10% inclusion levels. Multiple regression slope-ratio analysis of body weight gain regressed on dietary fat intake indicated that the relative bioavailability values (RBV) of palm oil 2 (80%) and choice white grease (85%) were significantly lower than the 100% for RCO (P < 0.05), whereas the RBV of the vegetable blend acid oil 2 (93%) was not significantly different from 100%. In general, both the precision-fed rooster assay and the limit-fed broiler chicken assay were able to detect differences in RME or RBV among lipids; however, using higher inclusion rates of 15 or 20% of the lipids may increase sensitivity of the rooster assay.
进行了三次斜率比精喂公鸡试验，其中公鸡以 0、5、10、15 或 20%（各试验水平不同）的精炼大豆油、精炼玉米油（RCO）、家禽脂肪、粗制大豆油、粗制玉米油、棕榈油、蔬菜混合酸油 1 和 2、大豆酸油、牛脂或优质白色油脂作为地面玉米日粮的一部分进行精喂。用回归分析斜率比法对经氮校正后的真代谢能与日粮脂肪水平进行回归分析，估算相对代谢能（RME）值。RME 值的计算方法是将试验脂质的回归系数除以参考精炼大豆油或 RCO（设定为 100%）的回归系数。公鸡试验的结果表明，只有棕榈油 1（83%）和牛脂（74%）的 RME 值显著低于（P<0.05）精炼大豆油或 RCO。结果表明，在 15%和 20%的较高添加水平下，不同脂肪源之间的差异通常更大。除了斜率比精喂公鸡试验外，还进行了限饲肉鸡生长试验。肉鸡从 11 日龄到 20 日龄以 70%的预期日采食量限饲，4 种脂质源（RCO、棕榈油 2、优质白色油脂和蔬菜混合酸油 2）以 0、5 和 10%的添加水平进行测试。用回归分析斜率比法对体重增加与日粮脂肪摄入量进行回归分析表明，棕榈油 2（80%）和优质白色油脂（85%）的相对生物利用率（RBV）显著低于 RCO 的 100%（P<0.05），而蔬菜混合酸油 2（93%）的 RBV 与 100%无显著差异。一般来说，精喂公鸡试验和限饲肉鸡试验都能检测到脂质之间的 RME 或 RBV 差异；然而，使用 15%或 20%的更高添加率可能会增加公鸡试验的灵敏度。
