Reduced Age at First Calving: Effects on Lifetime Production, Longevity, and Profitability

The time between birth and first calving represents a period in which replacement heifers are not generating income. Instead this rearing period requires considerable capital expenditures including feed, housing, and veterinary expenses. These expenses constitute 15 to 20% of the total expenses related to milk production (Heinrichs, 1993). A basic approach to reducing this cost is to reduce the amount of time between the heifer’s birth and her first freshening. Age at first calving (AFC) has a significant influence on the total cost of raising dairy replacements with older calving heifers being more expensive to raise than younger (Tozer and Heinrichs, 2001). Furthermore, reducing AFC can also improve the profitability of the enterprise by increasing lifetime milk production and milk production per year of herd life (Lin et al., 1988). AFC can be reduced by a combination of increasing prepubertal average daily gain and decreasing age at breeding (Gardner et al., 1988; Van Amburgh et al., 1998; Radcliff et al., 2000) or by reducing age at breeding alone (Lin et al., 1986; Ettema and Santos, 2004).