Recent study shows calving heifers at 22 to 26 months results in an increased lifetime milk yield and increased survivability. Heifer rearing represents a significant cost to any dairy farm. It is at least two years before a replacement starts milking and begins paying back the cost of rearing.

However, there is big variation in age of first calving (AFC) in the national dairy herd. With this in mind, we set about assessing the impact of AFC on milk production and survival.