Making use of high quality grass is very efficient for growth in youngstock if managed correctly, helping reduce rearing costs. However, ensuring that young heifers achieve the desired growth rate at grass relies on good grass management and knowing when to target supplementary feed.
Young heifers will benefit from being fed concentrates in their first season at grass, especially in the first few weeks following turnout and later in the season as grass quality and availability declines. Ideally heifers should be a minimum of 6 months old before going to grass and if less than 6 months, supplementary feeding in the region of 1 – 2 kg will benefit growth rates and the ability to cope with the challenges of grazing. The change from a controlled indoor environment and consistent diet, based on straw or conserved forage, to the variables of weather and fresh grass can be stressful. The younger the heifer, the less able they are to cope, resulting in more of a growth check. Supplementary feeding will also enable heifers to deal with any disease/parasite challenges.
According to AHDB Dairy’s latest Forage for Knowledge data from farms across the UK, grass quality averaged 12.7 ME and 23.4% crude protein on a dry matter basis in the first week of April. This is considerably more protein than is required for growth. Therefore, a high protein feed at grass is not necessary and low protein feeds including barley, beet pulp and soya hulls would be a cheaper option. A maximum 15% protein feed would be more than sufficient. To avoid digestive upsets do not feed more than 2 kg/head in one feed, especially if cereal is a major component, to reduce the risk of acidosis and maintain rumen health.
Aim to graze heifers at a height of no more than 4 inches or 10 cm, where the D value should be around 75%. This should be around a cover of 2,800 kg DM/ha. If turning out onto higher covers and heifers do not graze down to the desired residual, grass quality will suffer later in the season. When weather conditions are favourable, heifers will achieve good dry matter intakes and receive sufficient energy and protein to sustain growth rates of over 0.8 kg/day. However on wet days and unfavourable weather conditions, dry matter intake will suffer and it will be energy that is in short supply.
Stocking rates are important to make sure that grass is effectively utilised, especially early in the grazing season when grass growth rates are high. This will ensure quality is maintained throughout the summer. Suggested stock rates per hectare are shown in the table below:
|Heifer Weight (kg)
|April to June
|June to August
|September & October
Although more work and investment is required for fencing and water, rotational grazing as opposed to set stocking will not only achieve higher liveweight gains, it will also increase grass growth per hectare and improve utilisation. Being able to match grass supply to heifer requirements relies on measuring grass to know how much is available and estimated dry matter intakes (work on the basis of 2.5% of body weight in dry matter for heifers below 400kg).
Mineral supplementation will be necessary as grass will unlikely meet the requirements for trace elements alone. Many trace elements are involved in feed conversion and immunity and feeding minerals at grass will generally result in improved liveweight gains in the region of 10 – 15%.
Lorna MacPherson, email@example.com
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