When heifers calve very young, there is a greater risk of stillbirth and lower first-lactation milk production. When heifers are old at calving, their fertility may be negatively affected and it raises their culling risk. Plus, there is the cost of feeding them to that age before you get any return. So what is the sweet age for first calving to maximize average lifetime production? To answer that question, researchers at USDA analyzed production, reproduction, and lifetime data along with genetic (relationship) data from 13.9 million Holstein, 1.2 million Jersey, and 90,400 Brown Swiss cows. (Isn’t the national dairy database great? That’s just cows who first calved from 1997 through 2015!) Genomic data from ab
out 205,000 of those animals were also used.
One of the first interesting results of this study was documentation of the significant trend toward younger ages at first calving (see Table 1). It’s been most pronounced for Jerseys.
Table 1. Percentages falling into each age-at-first-calving (AFC) category in 1997 and 2012. (Data condensed from Hutchison et al. 2017.)
| AFC (months) |
Holstein
1997 2012 |
Jersey
1997 2012 |
Brown Swiss
1997 2012 |
| 18–22 |
7.9 |
33.5 |
18.5 |
65.2 |
3.0 |
12.8 |
| 23–27 |
66.8 |
58.3 |
64.2 |
31.1 |
53.5 |
59.2 |
| 28–35 |
25.3 |
8.2 |
17.3 |
3.7 |
43.5 |
28.0 |
Age at first calving may serve as an indirect indicator of general productivity and survivability, as lower ages at first calving correlate with higher lifetime production and fertility. That is, heifers capable of getting pregnant at younger ages may just be more robust animals in general. In order to capitalize on those individuals, one shouldn’t start breeding too late. The data support a target age of 21-22 months for Holsteins and Brown Swiss to deliver their first calves and 20-21 months for Jerseys. However, breeding at ages younger than 11-13 months is not recommended because younger heifers are more likely to have stillborn calves. The authors of the study suggest that AFC be incorporated in bull selection indexes, which would enable population-level selection for an AFC that increases profitability.
the article: Hutchison et al. Genomic evaluation of age at first calving. Journal of Dairy Science. August 2017. 100:6853–6861.
ges to the Margin Protection Program for dairy producers were made in the Bipartisan Budget Act of 2018. The Farm Service Agency has recently announced new implementation rules to accommodate the changes. Mark Stephenson and Andrew Novakovic, from the University of Wisconsin and Cornell University, will conduct a webinar to walk you through these changes and to assess impacts on producers who participate.
