The target is to maintain the linear growth achieved during the pregnancy phase.
The target body weight is 94% of the mature body at weaning (MBW). For a Holstein cow with a mature body weight of 650kg this means a weight of 611kg at 24 months of age, achieving an average daily gain (ADG) of approximately 800g per day.
The unborn calf is growing 75% of its total body weight in the last three months, meaning 300g/day. Keep in mind to feed the heifer sufficient nutrients, as both the heifer as well as the unborn calf need to grow.
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Calving for a heifer can be a stressful period. Producers can follow these tips to help smooth the transition from calving to the start of the lactation:
Within the lactation herd:
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
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.
The air around calves should be similar to the outside air. Stale air has a much higher viable airborne pathogen load.
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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*Mature Body Weight (MBW) of Holstein heifers is 650kg