Reducing dietary protein has been of interest to the global poultry industry to improve bird health, welfare, and industry sustainability. Low protein (LP) diets are typically glycine (Gly) deficient and produce poor performance. Supplementing the diet with Gly or precursors of Gly can overcome this deficiency. A feeding experiment was conducted with 330 Ross 308 off-sex males across 5 treatments in a randomized design using 11 birds per pen replicated 6 times. Grower and finisher treatments were fed from day 7 to 21 and day 21 to 35, respectively. The objective was to test the efficacy of supplementation with Gly and Gly equivalents (Glyequiv), serine (Ser) and threonine (Thr), in plant-based LP diets on bird performance against a standard protein (SP) diet containing meat and bone meal. Glycine, Ser, or Thr were supplemented on Glyequiv basis to an approximately 3% lower CP diet to achieve the same digestible Gly and Ser level as the SP diet. Nitrogen efficiency, serum uric acid, blood plasma amino acids (AA) and AA digestibility were also investigated to monitor potential metabolic effects. Birds fed the LP diet were only 3.3% lower in final body weight than the SP treatment (2,556 vs. 2,641 g) while the supplementation of Gly or Ser had no effect. Supplementation of Thr reduced final body weight by 9.5% (P < 0.05). Reducing CP increased N efficiency by 9.6% (P < 0.05) and decreased blood serum uric acid by 26.9% (P < 0.001) in the finisher treatments. Glycine and Ser supplementation in LP diets had no effect on these parameters. The LP diet reduced AA digestibility and blood plasma AA while the supplementation with either Gly, Ser, or Thr increased overall AA digestibility (P < 0.05) but had no overall effect on blood plasma AA. Further research is required into Gly metabolism; however, Thr supplementation depressed growth and therefore is not feasible to cover Gly deficiency in LP diets on a Glyequiv basis.

中文翻译：

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在肉型鸡的低蛋白日粮中补充甘氨酸、丝氨酸和苏氨酸。

减少膳食蛋白质一直是全球家禽业感兴趣的，以改善家禽健康、福利和行业可持续性。低蛋白 (LP) 饮食通常缺乏甘氨酸 (Gly) 并产生较差的性能。用 Gly 或 Gly 前体补充饮食可以克服这种缺陷。在随机设计中，对 330 只罗斯 308 异性雄性进行了 5 次处理，每栏使用 11 只鸡，重复 6 次进行喂养实验。分别从第 7 天到第 21 天和第 21 天到第 35 天饲喂生长者和育肥者处理。目的是测试在以植物为基础的 LP 日粮中补充 Gly 和 Gly 等效物 (Glyequiv)、丝氨酸 (Ser) 和苏氨酸 (Thr) 对鸡的性能与包含肉和骨粉的标准蛋白质 (SP) 日粮相比的效果. 甘氨酸，丝氨酸，在 Glyequiv 基础上将 Thr 或 Thr 补充到 CP 日粮中约低 3% 以达到与 SP 日粮相同的可消化 Gly 和 Ser 水平。还研究了氮效率、血清尿酸、血浆氨基酸 (AA) 和 AA 消化率，以监测潜在的代谢影响。饲喂 LP 饮食的鸡只的最终体重仅比 SP 治疗低 3.3%（2,556 对 2,641 克），而补充 Gly 或 Ser 没有效果。补充 Thr 可使最终体重减少 9.5% (P < 0.05)。在育肥处理中，降低 CP 可使 N 效率提高 9.6%（P < 0.05），血清尿酸降低 26.9%（P < 0.001）。在 LP 日粮中添加甘氨酸和 Ser 对这些参数没有影响。LP 饮食降低了 AA 的消化率和血浆 AA，而补充 Gly、Ser、或 Thr 增加了整体 AA 消化率（P < 0.05），但对血浆 AA 没有总体影响。需要对 Gly 代谢进行进一步研究；然而，Thr 补充剂抑制了生长，因此在 Glyequiv 的基础上弥补 LP 日粮中的 Gly 缺乏是不可行的。