Growth targets

The target is to maintain the linear growth achieved during the grower phase.

The target body weight is 55 – 60% of the mature body weight (MBW). For a Holstein cow with a mature body weight of 650kg this means a weight of 375kg at 13 months of age, achieving an average daily gain (ADG) of approximately 800g per day.

Month 13
Weight at 13 months, % MBW
55 – 60%
Weight at 13 months, kg *
375 kg
ADG, g/day
800-850 g
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Minerals and vitamins

A heifer’s mineral requirement remains roughly the same during phases 4, 5 and 6 – the grower, puberty and pregnancy phases. It’s extremely important to meet the needs of these young and growing animals. In many cases, the uptake of vitamins and minerals from the base ration is insufficient. Shortages of important trace minerals and vitamins are often the main cause of fertility problems and hoof problems. Minerals like selenium and copper are crucial to support fertility, as is vitamin E. Also, biotin and zinc have important roles in strengthening the hoof.

Mineral requirements for heifers (per kg of dry matter (DM))

< 8 months
8 – 12 months
> 12 months
Ca (g)
K (g)
Na (g)
Mg (g)
P (g)
Fe (mg)
100 – 150
50 – 100
50 – 100
Cu (mg)
10 – 15
10 – 15
15 – 20
Zn (mg)
50 – 100
50 – 100
50 – 100
Mn (mg)
50 – 100
50 – 100
50 – 100
Se (mg)
0,15 – 0,25
0,15 – 0,25
0,2 – 0,25
I (mg)
0,6 – 1
0,6 – 1
0,6 – 1
Co (mg)
0,25 – 0,5
0,25 – 0,5
0,25 – 0,5
Vit A (IU)
3000 – 4000
3000 – 4000
3000 – 4000
Vit D3 (IU)
300 – 500
300 – 500
300 – 500
Vit E (IU)
20 – 30
20 – 30
20 – 30


The mineral needs of the growing heifer are met with Rupromin Heifer. This mineral complements the young stock ration by offering a complete package of vitamins and minerals, combined in one bag, to support hoof health and bone and bodyframe development.

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It’s important to remember that heifers reach the puberty phase based on weight rather than at a pre-determined age. In practice, puberty can be reached anywhere between eight and 16 months, depending on growth rates.

Maintaining growth to achieve the growth targets based on percentage of mature body weight will help make sure that puberty is reached more than two months before breeding. As fertility improves up to the third oestrus cycle after puberty, they need to have grown sufficiently to reach puberty before the start of serving.

Maintaining the right energy and protein level is critical during this phase to ensure successful implantation of the embryo. Therefore, it’s important to calculate rations and analyse roughages. The heifer’s mineral requirements can be met by feeding a mineral that’s top dressed on the ration or mixed in the TMR, or by giving the heifers access to a mineral bucket.

Bull selection for easy calving and fast genetic improvement

Unfortunately, dystocia poses a major risk for future milk production, fertility and survival of first lactation heifers. Excessive calf birth weight is the largest contributing factor to dystocia, so careful bull selection is really important during this phase of the heifer’s development.

Heifers are the most ‘genetically advanced’ animals within the herd, so consideration should also be given to using these animals to breed future replacements.

Controlled breeding

It is worth considering the use of controlled breeding techniques during this phase to help improve fertility, ease management and to help control the time at which heifers will eventually enter the milking herd. Controlled breeding allows artificial insemination (AI) to take place at a convenient time for the unit, when labour and handling facilities are available.


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In a grazing system, heifers should experience going out on grass before they enter the main milking herd to avoid the stress of a new environment at this time.

From five or six months of age, calves can be grazed. It’s important to follow basic guidelines when they first go out to grass:

Heifers, like cows, like quality grassland. To achieve an age of first calving (AFC) of 24 months, they must get high quality feed – even when grazing.

Overall, grazing heifers offers benefits and an AFC of 24 months is achievable. It relies on high quality grass being made available that can provide the nutrients to match the heifer’s requirements at this stage. A successful grazing strategy for heifers will is good preparation for grazing as part of the milking herd at a later stage.













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General considerations

Good housing conditions contribute to efficient youngstock rearing and ensures their potential growth from the nutrients in the diet is achieved and not wasted by spending energy on staying warm or fighting off high pathogen loads. Poor housing conditions, such as poor ventilation, can lead to poor feed intakes, low growth rates and poor feed efficiencies. It can also have serious long term effects on lifetime lactation.

In general terms there are three simple principles for good housing conditions for each stage of the rearing period

(Low) Moisture

Excess moisture, originating from the animals and bedding, combined with heat is an ideal breeding ground for pathogens. This increases the risk of pneumonia so should be avoided. Excess moisture from leaking gutters, water troughs or broken buckets should also be avoided.

Fresh Air

The air around calves should be similar to the outside air. Stale air has a much higher viable airborne pathogen load.

Air speed

Fresh air is important but draughts are very dangerous. The right air speed will depend on the age and number of animals in the building. The air speed itself, within a barn, is the product of the air inlet and air outlet size and position. A smoke test will help to determine air movement in buildings.

All three principles can be controlled by The Stack Effect


The Stack Effect

The stack effect works by air flowing past the animals, which is warmed up through heat generated by the animals, and rising to the top where it leaves the building through the outlet. As the warm air leaves, negative pressure draws in fresh air from the inlets.

However, this only works if there is enough heat generated by the animals to create the effect. Youngstock create less heat than adult dairy cows and this needs to be taken into account. If, for example, the building is too wide for the number of stock being housed, the cool air can drop instead of leaving through the outlet. A smoke test can help determine whether the stack effect is working.


Appropriate lighting is important, especially during the breeding phase to stimulate the oestrus cycle. For housed animals, 10% of the natural light should be able to reach the pens from clear roofing panels. For artificial lighting conditions, the intensity should be between 100 and 200 lux. Artificial light should resemble natural lighting and follow the daily pattern of natural light.

Housing requirement for heifers

Ideally air should always flow from the youngest to the oldest animals and sick animals should be kept separately.

Heifers should be grouped according to size and weight and not just by age. Cubicles need to be designed to suit the animals at both the start and the end of the housing period. Animals must be able to lie down in the cubicles at any time. For younger animals is it advised to provide some bedding in the cubicles as concrete is cold.

Pregnant heifer should be introduced to the main dry cow group at least four weeks prior to calving. More tips on housing and a smooth transition into the dairy herd.


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Key element in phase
Target % MBW
Acquire passive immunity
Day 1 – 3
Initaite rumen development
Day 3 – 56
Maximise dry matter intake
Month 3
Optimise growth rate
Month 4 – 9
Control growth to improve fertility
Month 10 – 15
55 – 60
Maintain growth and nutrition
Month 16 – 23
Prepare for calving and lactation
Month 24
94 (7 days pre-calving)

*Mature Body Weight (MBW) of Holstein heifers is 650kg