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 offeed additives such as crude protein and phytase can enhance nutrient absorption, improvefeed 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, includ-ing the reduction of nitrogen and ammonia emissions, thereby supporting environmentallyresponsible poultry production.