Toghyani Mehdi, MacElline Shemil, Selle Peter H, Liu Sonia Y
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, 2006, New South Wales, Australia; Poultry Research Foundation, The University of Sydney, Camden, 2570, New South Wales, Australia.
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, 2006, New South Wales, Australia; Poultry Research Foundation, The University of Sydney, Camden, 2570, New South Wales, Australia.
Poult Sci. 2024 Dec;103(12):104361. doi: 10.1016/j.psj.2024.104361. Epub 2024 Sep 26.
A total of 2,400 day-old off-sex male Ross 308 chicks were used in a 4 × 3 factorial array (8 replicates with 25 birds per replicate) to determine the interactive effects of dietary metabolizable energy (ME) and amino acid (AA) densities on productive traits of broiler chickens reared to 42 d of age. The experimental factors were 4 ME levels (control, -50, -100, -150 kcal) and 3 digestible AA levels (control, +3.0 and +6.0%). Diets were fed for starter (0-10 d), grower (11-24 d), finisher (25-35 d), and withdrawal (36-42 d) phases, with consistent reduction of ME and increase in AA density for each phase. Overall, ME reduction did not compromise final body weight (BW; d 42). However, when ME was reduced by 50 kcal, only the diets with +6% AA density improved BW, resulting in an interaction between ME and AA levels (P < 0.05). Reducing ME and increasing AA densities independently increased total feed intake (P < 0.01). An interaction between ME and AA density on feed conversion ratio (FCR) was observed where increasing AA density at both +3.0 and +6.0% levels at control ME reduced FCR, but with reduced ME diets, FCR was reduced only at +6% AA density (P < 0.01). Quadratic broken line models estimated a digestible Lys to ME ratio (mg Lys/1,000 kcal ME) of 474 and 407 in starter and grower diets, respectively, to optimize both BW and FCR. However, in finisher phase a ratio of 363 could only be predicted for optimal FCR and in withdrawal a ratio of 349 to optimize BW. In summary, these results indicate that the interaction between ME and AA densities affects the productive traits of broiler chickens. Increasing AA density at control ME density improves FCR, while reduced ME diets require higher AA density to improve FCR. Quadratic broken line models suggest specific digestible Lys to ME ratios for optimizing BW and FCR across different phases of the production cycle.
总共2400只1日龄的罗斯308雄性雏鸡被用于4×3析因试验设计（8个重复，每个重复25只鸡），以确定日粮代谢能（ME）和氨基酸（AA）密度对饲养至42日龄肉鸡生产性能的交互作用。试验因素为4个ME水平（对照、-50、-100、-150千卡）和3个可消化AA水平（对照、+3.0%和+6.0%）。日粮分雏鸡期（0 - 10日龄）、生长期（11 - 24日龄）、育肥期（25 - 35日龄）和停饲期（36 - 42日龄）投喂，每个阶段ME持续降低，AA密度持续增加。总体而言，ME降低并未影响最终体重（BW；42日龄）。然而，当ME降低50千卡时，只有AA密度为+6%的日粮能提高BW，这导致ME和AA水平之间存在交互作用（P < 0.05）。单独降低ME和增加AA密度均会使总采食量增加（P < 0.01）。观察到ME和AA密度对饲料转化率（FCR）存在交互作用，即在对照ME水平下，AA密度增加至+3.0%和+6.0%时均能降低FCR，但在ME降低的日粮中，只有AA密度为+6%时FCR才会降低（P < 0.01）。二次折线模型估计，雏鸡期和生长期日粮中，可消化赖氨酸与ME的比值（毫克赖氨酸/1000千卡ME）分别为474和407时，BW和FCR均能达到最优。然而，在育肥期，仅预测出比值为363时FCR最优，在停饲期，比值为349时BW最优。总之，这些结果表明ME和AA密度之间的交互作用会影响肉鸡的生产性能。在对照ME密度下增加AA密度可提高FCR，而ME降低的日粮需要更高的AA密度才能提高FCR。二次折线模型给出了在生产周期不同阶段优化BW和FCR的特定可消化赖氨酸与ME的比值。
