Iqbal Waqar, Ayalew Habtamu, Li Siman, Wang Xiaocui, Xu Changchun, Yaqoob Muhammad Umar, Ali Awais, Zhang Haijun
Laboratory of Quality and Safety Risk Assessment for Animal Products on Feed Hazards (Beijing) of the Ministry of Agriculture and Rural Affairs, Institute of Feed Research, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
Laboratory of Quality and Safety Risk Assessment for Animal Products on Feed Hazards (Beijing) of the Ministry of Agriculture and Rural Affairs, Institute of Feed Research, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China; University of Gondar, College of Veterinary Medicine and Animal Sciences, Po. Box 196, Gondar, Ethiopia.
Poult Sci. 2025 Jul;104(7):105163. doi: 10.1016/j.psj.2025.105163. Epub 2025 Apr 13.
Global interest has emerged in implementing low crude protein (LCP) diets for poultry. The necessity of their development stems from low-cost formulation, maintaining egg quality, and environmental impacts, including health and welfare concerns for current egg production in the world. Researchers have conducted several studies to provide biochemical insights into the effect of LCP on laying hen diets, but practical limitations of LCP diets still exist. Supplementing laying hen feed with crystalline essential amino acids (AAs) like methionine, lysine, and threonine is standard industry practice. It has enabled a reduction of dietary crude protein (CP) to the standard level. However, research considering nonessential AAs like glycine (Gly) in LCP diets is still limited. Therefore, this review aims to enhance the understanding of LCP diets for laying hens, focusing on Gly. However, dietary Gly equivalents (Gly) for Gly represented the first-limiting nonessential amino acid in poultry diets. Targeted adjustment of essential AAs and Gly can considerably decrease CP in poultry diets. Gly is generally considered a nonessential AA in standard CP poultry diets. However, it becomes conditionally essential AA under dietary LCP situations. The variable requirement for dietary Gly suggested that its static recommendation in poultry diets provides high safety margins of Gly in the LCP of laying hen diets. These variable recommendations for dietary Gly in LCP diets would help optimize egg production and albumin quality and reduce nitrogen (N) emissions in poultry farms. The current review suggests that Gly could be a conditionally essential AA for laying hens fed with LCP diets.
全球对实施家禽低粗蛋白（LCP）日粮的兴趣日益浓厚。其发展的必要性源于低成本配方、维持蛋品质以及环境影响，包括对全球当前蛋生产的健康和福利问题。研究人员进行了多项研究，以深入了解LCP对蛋鸡日粮的影响，但LCP日粮仍存在实际局限性。在蛋鸡饲料中添加蛋氨酸、赖氨酸和苏氨酸等结晶必需氨基酸（AA）是行业标准做法。这使得日粮粗蛋白（CP）能够降至标准水平。然而，关于LCP日粮中甘氨酸（Gly）等非必需氨基酸的研究仍然有限。因此，本综述旨在增进对蛋鸡LCP日粮的理解，重点关注甘氨酸。然而，日粮中甘氨酸当量（Gly）代表家禽日粮中第一限制性非必需氨基酸。有针对性地调整必需氨基酸和甘氨酸可以显著降低家禽日粮中的粗蛋白。在标准粗蛋白家禽日粮中，甘氨酸通常被认为是非必需氨基酸。然而，在日粮低粗蛋白情况下，它成为条件必需氨基酸。日粮中对甘氨酸的可变需求表明，其在家禽日粮中的静态推荐为蛋鸡日粮低粗蛋白时提供了较高的甘氨酸安全边际。这些低粗蛋白日粮中对甘氨酸的可变推荐将有助于优化产蛋性能和蛋白品质，并减少家禽养殖场的氮（N）排放。当前综述表明，甘氨酸可能是饲喂低粗蛋白日粮蛋鸡的条件必需氨基酸。
