The nutrient composition of feed plays a crucial role in regulating gene expression in animals, thereby affecting growth, metabolism, and immune functions. In poultry, the optimized use of feed additives such as crude protein and phytase can enhance nutrient absorption, improve feed efficiency, and reduce environmental waste. In this study, we investigated the transcriptomic changes in the blood of forty-eight one-week-old broiler chickens fed diets differing in crude protein and phytase content. Using RNA sequencing and bioinformatic analysis, a total of 44 differentially expressed genes were identified in response to dietary variation. These genes were primarily involved in immune response, regulation of cell morphology, glycolytic process, and glycerolipid metabolism. Functional enrichment analysis revealed significant associations with cytokine–cytokine receptor interaction pathways, which regulate lipid metabolism, cellular proliferation, differentiation, and inflammatory responses. Moreover, decreased levels of crude protein and phytase were linked to alterations in protein autophosphorylation, amino acid biosynthesis, and energy metabolism pathways. These findings indicate that dietary modulation of crude protein and phytase levels can significantly influence metabolic and immune regulatory mechanisms in early-stage broilers. The appropriate feeding of feed additives (such as crude protein and phytase) not only improves nutritional deficiencies and feed efficiency issues in livestock, but also contributes to sustainable meat production, including the reduction of nitrogen and ammonia emissions, thereby supporting environmentally responsible poultry production.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    시험방법 개요
    RNA-seq 데이터 전처리 및 분석 방법
    유의한 차등 발현 유전자 기능분석
RESULTS
    1주령 육계의 사료 조건별 유전자 발현 비교
    육계 혈액 내 에너지대사관련 유전자 발현
DISCUSSION
결론
REFERENCES

• Hyunji Choi(Precision Animal Nutrition Division, National Institute of Animal Science, Wanju 55365, Korea)
• Han-Ha Chai(Precision Animal Nutrition Division, National Institute of Animal Science, Wanju 55365, Korea) Corresponding author
• Wonchoul Park(Animal Breeding & Genetics Division, National Institute of Animal Science, Cheonan 31000, Korea)
• Dajeong Lim(Department of Animal Resources Science, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea)
• Eui-Chul Hong(Poultry Research Center, National Institute of Animal Science, Pyeongchang 32111, Korea)