Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2012
Publication Date: 1/24/2013
Citation: Curran, R., Weigel, K., Hoffman, P.C., Marshall, J., Kuzdas, K., Coblentz, W.K. 2013. Relationships between age at first calving, herd management criteria and lifetime milk, fat, and protein production in holstein cattle. Professional Animal Scientist. 29:1-9. Interpretive Summary: Lingering questions remain about the most appropriate age of first calving for Holstein dairy heifers. This is a management question that must weigh the advantages (cost savings) of calving heifers at the most commonly recommended age (24 months) against the potential long-term consequences to the animal's future productive life that sometimes are associated with early calving. This study was based on a large database of 69,145 Holstein heifers, and indicates that some dairy producers achieve lifetime production benefits by reducing age of first calving to approximately 21 to 22 months, but other dairy producers do not. Conversely, extending age of first calving beyond 24 months offers no apparent gains in first lactation milk production or longevity, and lifetime production tends to be compromised. Our results suggest that a 21- to 22-month target for age of first calving may be appropriate for some dairy herds. Our results also suggest that, for many dairy herds, unknown management impediments exist that do not yield lifetime productive benefits to reducing calving age to less than 23 months. The present study was observational, and despite the large number of cows and herds that were utilized, the multitude of management practices utilized by dairy producers likely impacted the results. Results from this study suggest that universal age of first calving recommendations may not apply across all dairy herds. Data also suggest that controlled studies that divide heifers into age of first calving, milking frequency, and stall occupancy scenarios may be beneficial in understanding the dynamic herd effects of age of first calving on lifetime productivity.
Technical Abstract: Data from 69,145 Holstein cows that calved for the first time 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 four herd management criteria (HMC). The four HMC were: 1)3X milking-RHA=12,750 kg (3X-H), 2)3X milking-RHA=11,250 kg (3X-M), 3)2X milking-11,250 kg (2X-M), 4)2X milking, RHA= 9,250 kg (2X-L). For all HMC, a universal loss in first lactation milk, fat, and protein yield was observed when AFC < 23 mo. Compared to 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 x 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 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.