The effect of extended calving intervals in high-yielding lactating cows on milk production and profitability.

A field trial was conducted to examine the effect of extended calving interval (CI) on production and profitability of high yielding cows (n = 937). First insemination was performed at 154 and 93 d postpartum (pp), for treatment and control primiparous cows, respectively, and at 124 and 71 d pp for treatment and control multiparous cows, respectively. During the first experimental lactation, average daily value-corrected milk (VCM) yield was 28.