To calve at two years old, heifers must achieve an average daily liveweight gain of 0.8kg throughout the rearing period. This rate of growth requires a daily energy intake of around 70MJ, but this varies according to heifer age, weight and rearing environment.
If heifer growth rates fall behind at grazing it can be difficult to ‘catch up’, resulting in delaying first calving and significant additional costs. Taking time to ensure heifers are performing well at grass is key to keeping them on track so they hit their target weight and stature to calve at 24 months old.
Target heifer growth chart
| Weight (kg) | DLWG 0.5kg | DLWG 0.6kg | DLWG 0.7kg | DLWG 0.8kg | DLWG 0.9kg | DLWG 1kg |
|---|---|---|---|---|---|---|
| 100 - 150 | 32 | 34 | 37 | 40 | 44 | 48 |
| 150 - 200 | 39 | 42 | 46 | 49 | 53 | 58 |
| 200 - 250 | 45 | 50 | 54 | 58 | 62 | 67 |
| 250 - 300 | 53 | 57 | 61 | 66 | 71 | 77 |
| 300 - 350 | 59 | 63 | 68 | 73 | 79 | 85 |
| 350 - 400 | 65 | 70 | 75 | 81 | 87 | 94 |
| 400 - 450 | 71 | 73 | 82 | 88 | 95 | 102 |
| 450 - 500 | 77 | 82 | 88 | 85 | 102 | 110 |
Heifer performance
Understanding grass quantity and quality is the first step in monitoring heifer performance at grazing. Measuring grass covers and dry matter content will help ensure grazing is meeting heifers’ energy requirements.
Ley performance, as well as heifers, should be monitored throughout the grazing season. Remember, in some instances, even high-quality leys may not sustain heifer growth rates of 0.8kg/day throughout the grazing season.
Regularly weighing heifers will not only monitor their growth rates but will also help to understand their energy requirements. The energy required for heifers to meet target growth rates and sustain a daily liveweight gain of 0.8kg will change as heifer liveweights increase. Keeping track of heifer weights will allow producers to check that intakes are meeting heifer requirements, or whether additional feed is needed.
Buffer feeding
If grass intakes alone are not meeting heifer requirements, then any shortfall should be buffered with either forage or concentrate. Grazing measurements and heifer weights should be used to determine how much buffer feed is required to sustain a growth rate of 0.8 kg/day.
Grazing small groups of heifers based on their age or size can also help manage their intakes.
As the effects of any deficiencies may not be seen immediately, it can be easy to forget about vitamins and minerals. However, they play an important role in supporting heifer health, growth rates and fertility. By using a grazing concentrate, you can ensure that your heifers are receiving the right levels of supplementation, even when fed at low rates.
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Quality grazing of grass leys relies on good grazing management by keeping the plants leafy and actively growing while matching the supply of the livestock needs. Utilisation of grass is often below 50% but can be up to 80% with good management.
Calculating utilised dry matter (UDM) can offer a quick guide to the forage dry matter that the animal actually uses per hectare. Expensive equipment is not required to assess the grass growth, walking the paddocks and checking growth will help assess grass stocks.
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