Abstract: In modern dairy farm operations,heifers represent a core group alongside mature cows,accounting for approximately 30% of the total herd inventory and constituting the second-largest expense in farm rearing costs. The growth health status of heifers,the timing of breeding,and conception efficiency directly determine the economic benefits of farm input and output. From the perspective of overall farm production planning,the calving progress of heifers not only influences the average parity structure of the lactating herd but also plays a crucial role in ensuring the overall average milk yield of the herd. Industry practices indicate that the ideal age for heifers to first calve is 22~24 months. Achieving this goal requires heifers to possess excellent reproductive capabilities,and superior reproductive performance ultimately translates into higher milk production,thereby creating greater economic value for the farm.

Key words: Heifer, breeding rate, conception rate, age at first calving, economic benefits, timed artificial insemination