[Objective] This study aimed to analyze the effects of parity,season,and lactation stage on milk yield,milk protein percentage,milk fat percentage,urea nitrogen,and somatic cell count by examining the Dairy Herd Improvement（DHI）data of dairy cows in Fugu County in 2023. [Methods] A total of 13,289 DHI records of Holstein lactating cows from five large-scale dairy farms were selected. The data were grouped and analyzed using SPSS 23.0 software to assess the impact of parity,season,and lactation stage on milk yield and milk composition. [Results] Parity,season,and lactation stage significantly affected milk yield and milk composition（P< 0.05）. Milk yield and milk fat percentage in winter were significantly higher than in other seasons（P< 0.05）,while milk protein percentage in autumn was significantly higher than in other seasons（P< 0.05）. Urea nitrogen levels in summer were significantly higher than in other seasons （P< 0.05）,and somatic cell counts in summer and autumn were significantly higher than in other seasons （P< 0.05）. Milk yield in the 1-45 d lactation stage was significantly higher than in other stages （P< 0.05）. Milk protein percentage and milk fat percentage increased with lactation stage,peaking significantly after 305 d （P< 0.05）. Urea nitrogen and somatic cell counts were significantly higher after 305 d compared to other stages （P< 0.05）. As parity increased,milk yield first rose and then declined,peaking significantly in the second parity （P< 0.05）. Milk protein percentage initially increased and then decreased,with the second parity being significantly higher than others （P< 0.05）. Milk fat percentage first decreased and then increased,with the first parity being significantly higher than others （P< 0.05）. Urea nitrogen levels were higher in early and late parities but lower in the middle,while somatic cell counts showed an upward trend with increasing parity. [Conclusion] Parity,season,and lactation stage significantly influence the production performance of Holstein lactating cows in Fugu County. Adjustments in dietary nutrition and management practices based on these factors,along with the application of DHI data for targeted measures,can enhance dairy cow productivity and economic efficiency.

dairy cow  /  DHI  /  parity  /  season and lactation stage  /  iactation performance