Management of calving and grazing yields multiple benefits

In this article experts from the College of Agriculture, Food and Rural Enterprise and the Agri-Food and Biosciences Institute outline how setting the age at which heifers calve can and management of grazing systems have multiple benefits.

Manage grass to ensure high intakes, good utilisation of the sward and to meet target growth rates for replacement heifers.

Rearing dairy heifer replacements represents significant expense. Analysis of 2018 - 19 CAFRE benchmarking data has indicated that the average cost associated with rearing a dairy heifer is around £1,800.  

This is a very difficult time for dairy farmers with the Coronavirus pandemic and keeping this cost as low as possible is paramount. Costs can be reduced by managing these heifers to calve down at two years old, at between 540 kg and 580 kg live weight.  

Research has shown other benefits, in that heifers calving at two years of age have less calving difficulty, higher lifetime milk yield and are more likely to be milking at five years of age, than heifers calved at over 30 months.

Careful planning is required when managing heifer replacements at grass to ensure that they achieve growth and weight targets to successfully calve at two years of age.  Issues to consider include identifying appropriate performance targets, monitoring animal performance and setting up grazing systems to cope with difficult grazing conditions.  

Live weight targets are often used to assess the development of heifer replacements during the rearing process and ensure that they calve down successfully at two years of age.  Key targets for heifer replacements at various stages of development include:

• Spring born calves (3 – 4 months age) should be 100 – 125 kg live weight
• Autumn born calves (6 – 8 months age) should be 170 – 220 kg live weight
• Heifers approaching 15 months of age should be 360 – 400 kg live weight
• Typical live weight gain targets for heifer replacements at grass are 0.7 - 0.8 kg/ heifer/ day

The management strategy adopted will largely depend on the stage of development of young stock, grass availability and weather conditions.  Aim to put the heifer replacements into areas that have a pre-grazing grass cover approaching 3,000 kg DM/ha (average grazing cover over the grazing platform of around 2,100 kg DM/ha).

Turn out yearlings and older animals before younger calves.  Identify sheltered sites close to the farm yard for younger animals during their first grazing season. March born calves and younger calves not achieving target live weights should continue to be kept indoors for at least the early part of the grazing season.  

Dr Steven Morrison, researcher at AFBI, highlights the benefits of rotational grazing pointing to a study where heifers aged three to seven months were allocated to either a continual grazing system, six-day rotation system, or three-day rotation system. The heifers managed on the continual grazing system gained 0.64 kg/day whilst the rotationally grazed heifers achieved an extra 0.04 – 0.16 kg/day without concentrate supplementation.

If grazing in the same area as older animals, implement a leader-follower rotational system where young animals are allowed onto a paddock before the older animals as this will allow them to get the best grass and help minimise the risk of picking up gastrointestinal parasites. As calves are selective grazers, they should be offered fresh leafy grass and not remain in the same paddock for long periods.  A “calf paddock” where calves remain for the summer is not recommended. Calves should be offered grass with a pre-grazing cover of 2,500 to 3,000 kg DM/ha or 8 to 10 cm in height. 

Aim for grass intakes of approximately 2.4 per cent of body weight in dry matter (8.5 kg DM/head/day for 350 kg heifers).  A recent AFBI study of heifers managed in a rotational grazing system and allocated to pasture allowances of either 1.8, 2.4 or 3 per cent of bodyweight showed that grass utilisation decreased as pasture allowance increased and live weight gain increased. The study indicated that offering pasture at a rate of 2.4 per cent of live weight helps achieve a good balance between heifer performance and grass utilisation. See link https://www.afbini.gov.uk/news/pasture-allowance-guidance-replacement-heifers for further information on allocation of grass.

Following on from this, daily grass dry matter intakes to meet target growth rates are:

• Calves 3 to 4 months of age should consume 4.5 kg
• Calves 6 months of age should consume 6.5 kg
• Heifers at 15 months of age should consume 8kg
• Heifers at calving (24 months) should consume 11kg

If these levels of grass intake are not achieved then supplementary feeding will be needed to ensure the required weight for age targets are met.

Monitoring performance is important to ensure that live weight targets set at the start of rearing are being met.  Heifers should be weighed several times a year.  If suitable weighing facilities are not available, a weigh-band can be used.  Always ensure that there are adequate handling facilities to allow measurements to be taken in a safe manner.

Target wither height for Holstein/Friesian heifers at key stages:

• Calves 3 – 4 months of age should be around 85 – 95 cm
• Calves 6 months of age should be around 100 – 105 cm
• Heifers at 15 months of age should be around 115 – 125 cm
• Heifers at calving (24 months) should be around 125 – 135 cm

Decisions on supplementary feeding can be taken from the performance results.

If supplementation is needed, the level of meal feeding should be between 1 and 2 kg of concentrate (on a fresh weight basis) per head per day for younger calves. Where a calf is not keeping pace with the rest of the group, it should be transferred to a more appropriate group. The level of concentrate supplementation should be altered according to grazing, soil and weather conditions to ensure that target growth rates continue to be met. 

Young stock should be offered high quality, leafy grass swards throughout the grazing season. To allow this, topping may be necessary to remove dead, stemmy material, especially later in the grass season, to ensure high grass intakes and heifer live-weight gains.   Grass should be topped to a height of 5-6cm, similar to swards that are well grazed down.  Topping should be carried out immediately after heifers are removed from a grazing area as later topping will check the re-growth.

It is good practice mid-season to take out heifer paddocks, mow and round bale.  This removes stemmy material and enables a high quality, leafy regrowth capable of supporting a high level of animal performance. It also minimises the risk of a significant worm burden developing in the young stock. 

Plan effective vaccination and worm dosing to minimize the risk associated with clostridial diseases and intestinal parasites for heifer replacements at pasture. This is particularly important if ‘clean’ grazing is not available due to farm layout.

In the coming busy months, ensure the replacement heifer enterprise is given good attention and try to keep the costs of rearing as low as possible with emphasis on grassland management.

Discuss all aspects of heifer management with your local CAFRE Dairying Adviser who is available by telephone and email. Remember to keep yourself and family as safe as possible in the present difficult time.

Manage grass to ensure high intakes, good utilisation of the sward and to meet target growth rates for replacement heifers.

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