Relationships between age at first calving; herd management criteria; and lifetime milk, fat, and protein production in Holstein cattle

Data from 69,145 Holstein cows that calved in 2005 were evaluated to determine the influence of age at first calving (AFC) on first lactation and lifetime production in commercial dairy herds. A DHI database was divided into 4 herd management criteria (HMC). The 4 HMC were 1) 3X milking and rolling herd average (RHA) = 12,750 kg (3X-H), 2) 3X milking and RHA = 11,250 kg (3X-M), 3) 2X milking and RHA = 11,250 kg (2X-M), and 4) 2X milking and RHA = 9,250 kg (2X-L). For all HMC, a universal loss in first-lactation milk, fat, and protein yield was observed when AFC was < 23 mo. Compared with 24 mo, first-lactation milk yield was decreased, 166, 369, and 654 kg for heifers calving at 22, 21, and 20 mo, respectively. In contrast, AFC × HMC interactions were observed for all herd-life and lifetime production criteria. In 3X-H and 3X-M herds, herd-life and lifetime DIM increased with decreasing AFC. In 2X-M and 2X-L herds, herd-life and lifetime DIM increased when AFC was reduced from 30 to 24 mo, but herd-life and lifetime DIM were not increased when heifers calved < 24 mo. In 2X-M and 2X-L herds, the combined effect of reduced first-lactation milk yield and with no corresponding benefit in lifetime DIM resulted in reduced lifetime milk, fat, and protein yields when AFC was < 23 mo. In contrast, increased lifetime milk, fat, and protein yields were observed in 3X-H and 3X-M herds when AFC was < 23 mo. Data suggest HMC alters the relationship between AFC and lifetime milk, fat, and protein production in commercial dairy herds.