Updated: June 9, 2021
By Sarah Potts

Do your heifers measure up? Tips for Evaluating your Heifer Program

Raising a replacement heifer to first calving is often the second or third largest expense on the dairy. Thus, it is important to fine-tune the heifer program to optimize heifer productivity and economic return. While the pre-weaned calf management program is a critical component of good heifer management, remember that management after weaning is also important.

Heifer Management Benchmarks

As with any business, benchmarks can help provide performance targets to aim for. However, it is important to keep in mind that every farm is different and operates under different circumstances and constraints. While it is tempting, avoid using benchmarks merely to compare your farm to your neighbor’s. Use them instead as guidelines to establish goals for your farm and tools to evaluate your progress toward those goals.

Age at first calving

Most producers have some knowledge of how old their heifers are at first calving, which is a metric that can provide valuable first-glance insight to the success of the heifer program. The Dairy Calf and Heifer Association indicates that Holstein heifers should calve at 21-24 months and Jersey heifers should calve at 20-22 months for optimal economic return. Research shows that for Holsteins, first lactation milk yield is maximized when heifers calve between 22 and 25 months of age.  There is no evidence that calving beyond 25 months improves first lactation milk yield or productive life.  If you want to reduce your age at first calving, you will need to determine if your heifers are large enough to be bred at an earlier age.  If they aren’t, then you may need to make adjustments to your nutrition and management to get them to the appropriate size by the desired breeding age. 

First lactation peak milk

Focal point

Heifer Benchmarks:

  • Heifers should be at least 85% of mature weight at first calving and 55% of mature weight at breeding
  • Holsteins: 21-24 months old at first calving; Jerseys 20 - 22 months old at first calving
  • First lactation peak milk at least 75% of peak milk for 3rd+ lactation cows

Tips for Success:

  1. Record age at first calving
  2. Weigh mature cows
  3. Weigh heifers at weaning, breeding, and calving


Like age at first calving, peak milk, which is the highest milk production test for a cow during the first 150 days of lactation, should also be a used in the initial assessment of the heifer program.  As a rule of thumb, peak milk production for first lactation cows should be at least 75% of peak milk for mature cows (3rd and greater lactations).  If it is not, then some investigating into the heifer program is warranted.  Heifers may not be large enough at first calving, have low body condition, or have mastitis or other health issues.

Size at First Calving

The ideal size at first calving will vary from herd to herd.  The Dairy Calf and Heifer Association recommends heifers calve in at approximately 85% of mature weight.  For a Holstein herd whose average mature cow weighs approximately 1,500 pounds, this is a target of 1,275 pounds.  For a Jersey herd whose average mature cow weighs approximately 1,000 pounds, this is a target of 850 pounds. 

It has been well-established that heifers that are bigger at calving tend to produce more milk during their first lactation.  However, a recent collaborative study between Penn State University and University of Florida showed that although weight at first calving did tend to be related to first lactation milk production, there was no significant difference in cumulative milk production throughout the first and second lactations.  Additionally, heifers who calved in at the heaviest weights lost substantially more weight in the first 30 days in milk and were 50% more likely to be culled relative to their lighter-weight counterparts.  The researchers concluded that the ideal weight at first calving which balances high milk production potential with health and longevity may be closer to 72 to 77% of mature weight.

Size at Breeding

The ideal size at breeding will vary from farm to farm depending on the mature size of the cows.  To ensure that they are physiologically capable of sustaining a healthy pregnancy and rate of growth to achieve an appropriate size at first calving, the Dairy Calf and Heifer Association recommends that heifers be at least 55% of mature weight before they are bred.  For a Holstein herd whose average mature cow weighs approximately 1,500 pounds, this is a target of approximately 825 pounds.  For a Jersey herd whose average mature cow weighs approximately 1,000 pounds, this is a target of approximately 550 pounds.

Setting Yourself up for Success

Below are three steps you can take that will set you up to easily evaluate your program, identify areas of opportunity, and set goals.

  1. Record age at first calving if you aren’t already.  This is a relatively simple metric that can be tremendously useful.  Your desired age at first calving will dictate breeding age.  If you wish to adjust your age at first calving, note your new goal and determine how you will get there.
  2. Record the size of your mature cows which are those that are 3rd lactation or greater.  This is an important metric that will help you estimate appropriate heifer sizes for breeding and calving.  If you do not have access to a scale, a weigh-tape measurement is better than no measurement at all.  Once you know how big your heifers should be at breeding and calving, then you have an idea of the growth rates needed in order to attain the those weights by your desired breeding and calving ages.
  3. Weigh your heifers (or use an appropriate weigh-tape) at weaning, breeding, and first calving.  These are useful measurements than can be used to evaluate the program and identify any shortcomings.  This practice can help you to determine whether heifers are meeting the growth targets you’ve set.  If targets aren’t being met, then having these measurements can help you identify which specific parts of the heifer program need work.

Putting it into Practice

Once you have established your goal for age at first calving, you must then estimate ideal heifer size at breeding and first calving.  If a Holstein herd has an average mature cow size of 1,600 pounds, then on average, heifers should be at least 880 pounds at breeding (0.55 × 1,600 pounds) and 1,360 pounds at first calving (0.85 × 1,600 pounds).  If the target age at first calving is 24 months, then the target age at breeding would be somewhere around 14 to 15 months (24 months of age – 9.2 months for pregnancy).

Equation 1: Daily gain required from weaning to breeding
    Target breeding weight - Weaning weight       
Age at breeding (days) - Age at weaning (days)
Equation 2: Daily gain required from breeding to calving
Target calving weight - Breeding weight
                           280 days

Two simple equations can then be used to determine the growth rate(s) required to achieve these targets.  Equation 1 calculates the rate of gain required after weaning to reach an appropriate breeding weight while equation 2 calculates the rate of gain required to after breeding to reach an appropriate calving weight.  Equation 1 does require you to know the average age and weight of calves at weaning.

In our example, if the target weight at breeding is 880 pounds and calves weigh 190 pounds at weaning at 8 weeks of age, then heifers need to gain 1.73 pounds per day after weaning to reach this target by 15 months [(880 lb – 190 lb) ÷ (456 days – 56 days)].  If the target weight at calving is 1,360 pounds, then heifers need to gain 1.7 pounds per day after breeding to reach this target [(1,360 lb – 880 lb) ÷ 280 days]. 

Take Home Message

The old adage “you can’t improve what you don’t measure” definitely holds true here.  Because raising heifers is an expensive part of dairy farming, it is a good idea to periodically evaluate the program to see if improvements can be made.  Paying attention to age at first calving and size at calving and breeding relative to mature cow size are useful metrics that can help provide a snapshot of the heifer program.


This article appears on the June 8, 2021, Volume 2, Issue 2 of the Maryland Milk Moo's newsletter.

Maryland Milk Moo's, June 8, 2021, Vol.2, Issue 2

Maryland Milk Moos is a quarterly newsletter published by the University of Maryland Extension that focuses on dairy topics related to Nutrition and Production, Herd Management, and Forage Production. To subscribe to this newsletter, click the button below to enter your contact information.