PS10-13. Effects of Low-protein Amino Acid-balanced Diets on Growth Performance, Protein Metabolism-related Gene Expression, and Gut Microbiota Structure in Yellow-feathered Chickens.

Abstract

This study aimed to investigate the effects of partial essential amino acid (methionine, tryptophan, arginine, isoleucine) removal from a low-protein diet on growth performance, physiological and biochemical indicators, amino acid transport, intestinal microbiota, and plasma free amino acid profiles in yellow-feathered chickens aged 1-30 days. A total of 1,080 1-day-old female medium-growing yellow-feathered chickens were randomly divided into 6 groups: normal protein group (SD, CP 20.5%), low-protein group (LP, CP 18%), and low-protein groups with removal of 20% methionine (LP-MET), tryptophan (LP-TRP), arginine (LP-ARG), and isoleucine (LP-ILE). Each group consisted of 6 replicates, with 30 chickens per replicate, the experiment lasted for 30-days. The results showed: (1) Growth performance: The final body weight (FBW) and average daily gain (ADG) of the LP group were significantly lower than those of the SD group (P < 0.05). The LP-ARG group exhibited the lowest FBW and ADG and the highest feed conversion ratio (FCR) (P < 0.05), while the LP-ILE and LP-MET groups showed significantly higher protein deposition rates compared to the SD and LP groups (P < 0.05). The LP group exhibited elevated plasma triglycerides (TG), blood urea nitrogen (BUN), and growth hormone (GH), as well as decreased insulin-like growth factor-1 (IGF-1) (P < 0.05). Removal of MET or TRP reduced TG to SD group levels, while removal of ARG or ILE decreased BUN (P < 0.05). The LP-ARG group showed the highest liver alanine aminotransferase (ALT) activity (P < 0.05). The jejunal expression of neutral amino acid transporter (B0AT) and excitatory amino acid transporter 3 (EAAT3) in LP group was significantly upregulated (P < 0.05), with partial recovery after specific amino acids were excluded. The LP group exhibited reduced α-diversity in the cecum microbiota and a decreased ratio of Firmicutes to Bacteroides (P < 0.05). The LP-MET group showed enrichment of beneficial bacteria such as Faecalibacterium, while the LP-TRP group demonstrated enrichment of Firmicutes phylum. The LP-ARG and LP-ILE groups exhibited a trend toward diversity recovery. Furthermore, the LP group exhibited reduced levels of taurine (Tau) and cysteine (Cys) (P < 0.05), with differential responses observed across amino acid restriction groups (e.g., elevated threonine in the LP-MET group and decreased arginine in the LP-ARG group). In summary, arginine restriction in LP diets had the most significant growth inhibitory effect, whereas ILE and MET restrictions could enhance protein deposition. These findings suggest the need for precise amino acid balance to optimize production performance and health in yellow-feathered broilers fed low-protein diets.

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