[目的]统计2014—2024年出生后备牛4 个生产阶段称重数据和产奶数据,第一,分析近10年各阶段体重（kg）、平均日增重（kg/d）变化情况;第二,分析体重与平均日增重关系、两者与头胎产奶量的关系。[方法]平均日增重计算方法一：（某阶段体重-出生重）÷日龄;平均日增重计算方法二：（指定阶段体重-前一阶段体重）÷（指定阶段称重日期-前一阶段称重日期）,分析后备牛生长发育情况和初产生产性能。[结果]（1）后备牛断奶平均日增重由2015年0.80 kg/d增长至2023年0.88 kg/d;初产体重上升,初产日龄下降。（2）各阶段平均日增重存在较大差异,断奶平均日增重0.85~1.00 kg/d,转育成平均日增重最大0.95~1.10 kg/d,转参配平均日增重0.86~0.96 kg/d,初产平均日增重最低0.75~0.83 kg/d。（3）初产体重越大的牛只,头胎305 天产奶量和高峰产奶量越高,但牛只多数集中在（550,600]kg（A组）,（600,650]kg（B组）体重范围内（占比70.5%,其中48.6%牛只在660~690 日龄内）。（4）A、B两组断奶体重、平均日增重差异不大,但转育成、转参配阶段,两组牛只体重差异逐渐拉大,B组初产体重高出A组45 kg左右;随日龄增加,A、B两组平均日增重差异逐渐明显,B组初产平均日增重较A组高60 g/天。（5）660~690 日龄分组（22~23 月龄）,B组305 天产奶量较A组高约360 kg,高峰产奶量高约1.3 kg;B组305 天产奶量较C组（500,550]kg,高出约848 kg,高峰产奶量高出约3.3 kg。[结论]为实现后备牛在22~24 月龄达到初产体重600~650 kg（产前体重640~690 kg）,牧场管理者需定期监测后备牛体重和评估日粮,监控生长发育状态,平衡日龄与体重关系,为后备牛提供充足但不过量营养摄入量,确保最佳发育状态,发挥生产潜力。

[Objective] By analyzing four body weights（BW,kg）in four phases of heifers'; life and milk production data from 2014 to 2024.The first objective was to analyze the changes of BW and average daily gain（ADG,kg/d） over the past decade,while the second was to examine the relationship between BW and ADG,as well as their correlation with primiparous milk yield. [Method] ADG calculation method 1：（weight at a designated phase-birth weight）÷age of days;ADG calculation method 2：（weight at designated phase-weight at previous phase）÷（weighing date at designated phase-weighing date at previous phase）,analyzed heifers'; growth and development status and their primiparous milking performance. [Result]（1）Weaning ADG increased from 0.80 kg/d in 2015 to 0.88 kg/d in 2023,first calving BW had increased,while the age at first calving had decreased.（2）There were significant differences in ADG at each phase.Weaning ADG ranged from 0.85 to 1.00 kg/d,maximum ADG was 0.95~1.10 kg/d which during transfer phase,first breeding ADG was 0.86~0.96 kg/d,and minimum ADG was 0.75~0.83 kg/d during first calving.（3）The larger first calving BW,the higher 305-d milk yield and peak milk yield.However,most cows'; first calving BW was concentrated in （550,600]kg（Group A） and （600,650]kg（Group B）（accounted for 70.5%,48.6% of them at the age of 660 d to 690 d）.（4）There was no significant difference in BW and ADG between Group A and Group B at weaning phase,but during the transfer and first breeding phase,the differences in BW gradually widened.First calving BW of Group B was about 45 kg higher than Group A';s.With the age increases,the difference in ADG between Group A and Group B became increasingly evident.First calving ADG of Group B was 0.06 kg/d higher than Group A's.（5）At the age of 660~690 d（22~23 m）,305-d milk yield of Group B was approximately 360 kg higher than Group A's,peak milk yield of Group B was approximately 1.3 kg higher;305-d milk yield of Group B was approximately 848 kg higher than Group C（500,550]kg,peak milk yield of Group B was approximately 3.3 kg higher. [Conclusion] To achieve first calving BW 600~650 kg（pre-calving BW 640~690 kg） for heifer at the age of 22~24 m,farm managers need to regularly monitor heifers'; BW and evaluate the diet to monitor their growth status and balance the relationships between age and BW.This will provide sufficient nutrient intake for heifer,to ensure maximizing their production potential under optimal developmental conditions.