FEEDING FOCUS May 2016 • Issue 15
Heifers at grass Getting heifers of the right weight and stature for 24 month calving requires an average weight gain of 0.80kg/day throughout the rearing period. Calving down at the right weight for age is critical for future performance. For every extra kg of bodyweight at calving, heifers will see an average increase of 14.5kg of milk in their first lactation. An additional 70kg of bodyweight equates to an extra 1,000kg of milk in the first lactation - see Figure 1. Figure 1 - Average increase of milk yield per kg BW.
Achieving this performance at grass can be a challenge, but it is entirely possible to obtain the desired weight gain whilst maximising use of grazed grass with the correct feeding and management systems in place. Dry Matter Intakes A heifer’s dry matter intake (kg/day) is relative to her body weight. For a heifer to achieve her required dry matter intake from grazed grass alone it makes sense that the required quantity of grass must be available. Measuring grass cover will highlight the amount of concentrate or forage required to buffer any shortfall.
Milk yield in first 300 DIM (kg)
Monitor energy intakes Depending on the age, weight and rearing environment of a heifer, she will require a daily intake of approximately 70MJ of energy in order to achieve a 0.8kg daily growth rate. There will be times during the grazing season when even the best quality grass will not provide the energy levels required to maintain desired daily growth rate targets. It is essential to assess the amount of energy heifers are obtaining from grass and buffer feed with concentrates when shortfalls in energy supplies are suspected. Bodyweight at calving (kg)
Meeting heifer growth targets As with all grazing cattle, dry matter intake is crucial for heifers at grass says Rachael Kennerley, ForFarmers Calf & Heifer Specialist. An average daily live weight gain (DLWG) of 0.80kg is required throughout the rearing period to allow heifers to calve at 24 months and achieving this level of performance at grass can be challenging. Ensure heifers are gradually transitioned on to a grazing diet to allow adaptation of the rumen. Do not expect a heifer to go out and immediately graze enough grass to meet all her energy requirements. Excess protein Heifer rations aim to have a protein content of around 16 per cent and with grazed grass often recording a crude protein (CP) content of more than 20 per cent, it is unlikely you will need to supplement heifers with high protein concentrates whilst they are at grass. If you do need to buffer feed with concentrates to help meet a heifer’s energy requirements, remember that low protein, high digestible fibre products are most suitable and have been specifically designed to complement heifers at grass. Maintain supply of vitamins and minerals Whilst deficiencies in vitamin and mineral provision don’t have an immediate and obvious impact on heifer performance, inadequate supplies do have a negative impact on the long-term health, growth rate and fertility of heifers. To ensure heifers are obtaining adequate levels of vitamins and minerals whilst they are at grass, regular supplementation is recommended. Grazing concentrates often have high vitamin and mineral content and can help maintain good levels of supplementation even when fed at low rates. Regular weighing Weighing your heifers throughout the grazing season is a good way to ensure that they are on track to achieve growth targets prior to being brought in for winter. By regularly monitoring weight gains, you can adapt supplementary feeding to ensure heifers are provided with the right level of nutritional support whilst maximising grass.
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It is not just about the amount of grass available to the youngstock, it’s also about the dry matter content. If grass dry matter is only 15%, there may be plenty of grass available, but a 12-month old heifer would need to eat 60kg fresh weight to meet her needs and this would be physically impossible. Dry matter can vary dramatically depending on weather and time of the year, so make sure you know the value of your grass and supplement as necessary. ForFarmers weighing trials demonstrated the following on grazing heifers: Feeding regime
Average DLWG
Grazing + 1kg VITA Heifer compound
0.96kg/day
Grazing only
0.44kg/day
Failing to achieve growth targets at grass could result in at least a one-month delay to service, resulting in an additional cost of up to £90 per heifer.
For more information about managing heifers at grass, please contact your ForFarmers account manager or calf and heifer specialist.
www.forfarmers.co.uk