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Forgotten age: Are developing heifers reaching full potential?

Gary Geisler Published on 27 February 2015
dairy cows feeding

Birth through 12 weeks old is a critical time in establishing the lifetime growth potential of a calf, and feeding strategies weeks 12 to 24 are essential to optimal rumen development.

As a result, it is not surprising that this age group is where resources are invested most heavily when it comes to raising calves.



But what about those heifers after they’ve reached 24 weeks old? This group of developing heifers are often referred to as the forgotten age, as many calf and heifer-raisers tend to put them on auto-pilot until they are ready to calve.

In the roughly 18 months post-grower stage, developing heifers undergo an incredible physiological transformation, transitioning from a focus on growth to preparing themselves for breeding, gestation and parturition, and lactation.

As heifers approach puberty, key nutrient demands increase. While less energy is needed in the diet for growth and maintenance, heifers do require essential vitamins, minerals, protein and amino acids to prepare for reproduction.

Developing heifers are more self-sufficient than younger calves, but there are a number of stresses introduced as heifers mature that can increase the need for these key nutrients.

Moving from calf pens to heifer breeding pens or pastures, commingling with new animals, running through cattle chutes, vaccinations and significant dietary changes can all contribute to a heifer’s increased stress.


Despite significant physical changes and added stress, heifers still must continue growing and developing so they are ready to enter the lactating herd. The key to extending the growth benefits achieved in superior calf feeding programs through breeding to prefresh is offering a convenient, consistent and balanced heifer ration.

Frequent heifer ration bottlenecks

Inadequate and inconsistent nutrient levels in heifer rations are seen more often than not. Feeding this group of heifers lactating herd “refusals” is a common and convenient practice on many dairies as it can seem like a short-term economical solution, since less feed is wasted.

However, a diet comprised of lactating ingredient refusals is not likely to have the essential nutrient profile developing heifers require. Improper delivery of an ideal nutrient profile may create nutrient shortages in the diet, which has the opportunity to reduce frame size, wither height and overall growth of the heifer.

Feed refusals typically do not have adequate protein and mineral levels to support heifer growth and development. Research has shown that organic trace minerals can help to increase growth rates, improve first-lactation milk yield and offer greater support for reproductive performance.

If growth rates can be improved, cost per kilogram of gain may be reduced, optimizing heifer-rearing cost and profitability.

It is unlikely that feed refusals will be thrown out, but consider offering them to another group, such as finishing steers, or even selling them to a neighbour.


If feed refusals must be fed to heifers, producers should evaluate the ration for nutrient content regularly and supplement accordingly, either with a mineral supplement, a lick tub or with a nutritional base mix that can be added directly to the ration. It is also important to set growth benchmarks and monitor growth rates to evaluate growth efficiency.

Heifers raised on pasture can also face nutritional shortages, especially as the quality of pastures begin to wane. Forages grown in drought conditions will have altered nutrient profiles and the protein-to-fibre ratio will be significantly decreased.

Lick tubs are quickly becoming a go-to item for dairy heifer-raisers who use pastures because they offer a convenient source of key nutrients formulated for developing dairy heifers.

A quality weather-resistant lick tub can help support grazing diets with added protein, vitamins and minerals to keep heifers growing efficiently. Many tubs are now available with larvicides, which if introduced early in the season, can help cut down on fly populations.

Impact of nutrition on reproduction

Dairy heifers tend to be the most fertile group of animals on the majority of operations. For many dairies, the number one priority once heifers are large enough to breed is to get them pregnant. Offering adequate crude protein, energy, vitamins and trace minerals has been shown to influence ovarian function, fertility and embryo quality in dairy animals.

A summary of five research studies showed that providing a supplement of zinc, magnesium, copper and cobalt resulted in fewer days open, higher pregnancy rates and fewer services per conception.

Heifer nutrition also plays a role in helping support greater hoof and claw health, which has been shown to influence heifer reproduction. Hoof health issues that originate in heifers may not become apparent until those animals enter the lactating herd.

Nearly 95 percent of large dairies (greater than 500 head) have reported digital dermatitis infections. Supplementing developing heifers with trace minerals has been shown to decrease the incidence and severity of white line separation by up to 35 percent, sole ulcers by up to 80 percent and claw lesions by up to 17 percent at 60 days after calving.

To ensure heifers are receiving the vitamins and trace minerals needed for efficient reproduction, include a mineral supplement (bagged or lick tub formulated for developing dairy heifers) into the ration.

Providing adequate supplemental protein is also recommended to help support reproductive development. Extra protein can be integrated into heifer diets in the form of a protein lick tub or by supplementing the heifer ration with a high-protein base mix.

Prefresh heifer nutrition

In the months leading up to calving, it is important to focus on body condition. Prefresh heifers should be fed a ration that allows them to achieve a body condition score of 3 to 3.5 to reduce the incidence of metabolic disorders post-calving.

Fat heifers (body condition score of 3.75 or greater) often experience lower dry matter intakes pre-calving and post-calving, and increased incidence of energy-related disorders such as ketosis and displaced abomasum.

Thin heifers (body condition score below 2.75) often underperform because they extend the period of time they are in a negative energy balance, and their calves typically are less vigorous and can have a reduced ability to absorb immunoglobulins.

To allow for continued growth and development, consistent dietary protein should be available in the prefresh heifer ration. Increased levels of protein in the diet have shown to support increased milk production and more 3.5 percent fat-corrected milk during the first 120 days of lactation.

Calf and heifer raisers spend the majority of their time working through calf nutrition strategies, but heifers spend 75 percent of their life in the developing heifer stage before entering the lactating herd. The key to moving heifers through this growth phase efficiently is to keep stress levels low and developmental needs top of mind when considering ration changes.

The cheapest ration doesn’t always mean it is the most economical one. First-calf heifers make up 30 to 50 percent of calvings on many dairies; making sure these heifers are developed and ready to hit the ground running once they calve will help them reach their full genetic potential so dairy producers can receive a healthy return on their calf and heifer nutrition investment.  PD

References omitted due to space but are available upon request. Click here to email an editor.

This group of developing heifers are often referred to as the forgotten age, as many calf and heifer raisers tend to put them on auto-pilot until they are ready to calve. Photo by PD staff.

Gary Geisler
  • Gary Geisler
  • Calf and Heifer Specialist
  • Purina Animal Nutrition