15:45Improvement through grassland management

Rearing heifers at grassRearing spring-calved heifers to calve at around two years of age from grazed grass is the specific challenge addressed by these advisory notes, although the issues are relevant to all rearing regimes.

For the greatest economic value, heifers need to be grown to an adequate size for successful bulling at 15 months of age to calve down at about two years old.

This is essential in block-calving herds and desirable for those with a greater spread of calvings.

Practical grass-based heifer rearing systems achieving this target, developed primarily in Ireland and New Zealand, are operated successfully by many UK herds.

Setting Growth Targets

Clear liveweight targets, with gains required to achieve them over the rearing period, are essential to ensure maturity is reached in time to serve the animals and get them in good enough condition to calve down (Tables 1 & 2).

The critical weight targets to achieve are at the end of the first six months of life and at 15 months of age when the heifers need to be bulled.

Table 1: Heifer Rearing Targets for the Main Dairy Breed

Holstein Friesian Jersey

Age (months) Weight (kg)Withers

Height (cm)Weight (kg)

Withers Height (cm)

Weight (kg)Withers

Height (cm)

2 76 87 72 84 55 78

3 110 93 100 88 75 82

4 127 96 120 93 95 89

6 180 104 162 100 130 94

12 340 124 285 118 220 109

15 (mating) 420 129 350 122 265 114

16 440 131 370 126 280 117

18 490 133 405 130 305 119

21 545 137 470 132 355 120

22 586 138 490 133 362 121

24 (pre-calving) 636 140 535 134 395 122

24 (post-calving) 568 140 485 134 350 122

Factsheet 14

15:46 Improvement through grassland management

Table 2: Heifer Growth Targets

Age/stageProportion of Mature

Weight (%)

6 months 30

9 months 40

Mating 55-60

Pre-calving 90

Post-calving 85

Second calving 92

A simple line graph can be drawn to establish weight for age targets for any type of heifer using the calf birth weight at one end and desired calving weight at the other (approximately 90% of the mature weight).

Specific levels of daily grass intake are required to achieve these targets (Table 3).

Table 3: Heifer Intakes of Good Quality Grazing for Target Growth Rates (Table 2)

Rearing Period

Calving at 500kg

Calving at 600kg

Dry Matter Intake (kg/day)

1.5-3 months 2.7 3.1

3-6 months 4.2 4.9

6-12 months 6.6 7.1

12-15 months (bulling)

7.9 8.6

15-23 months 9.9 10.5

23 months - Calving

10.7 11.5

If these levels of consumption prove impossible, supplementary feeding will be needed to ensure the required weight for age targets are met.

Concentrate supplementation may be necessary if target growth rates are not being achieved.

Feeding Calves

Heifer calves should be given at least 2 litres of colostrum at birth and reared on a regular system to about 4-6 weeks of age.

The calves can then be turned out into a sheltered field and fed cold milk once a day from a ‘milk bar’ (approx 4.5 litres/head/day) with good hay always on offer.

Young calves settle more rapidly to this system and do not wander far away.

They should always be offered the best grass and moved-on daily, ideally being kept about a week ahead of the cows in the grazing rotation and well separated from them to avoid disturbance.

When the calves reach about 90kg liveweight (at around three months of age) they should be weaned on to grass-only diets.

Concentrate feeding should be unnecessary but it is advisable to check weights frequently to ensure growth rates are being sustained (perhaps using weigh bands).

Managing Grazing

To give them top quality grass sufficient to sustain the required growth rates, calves should be rotationally grazed ahead of the cows until mid-summer.

At this stage they should be well-grown and can stand slightly tougher grazing conditions.

From August of their first summer the calves can be block-grazed and moved less frequently.

They will not suffer from having a slightly slower growth rate at this stage of their lives.

15:47Improvement through grassland management

Providing they are meeting their target growth rates the young-stock can safely be kept outside over their first winter on block grazing or forage crops.

They do, however, need to be offered adequate dry matter and may need to be moved regularly to ensure they do not poach fields badly.

Some hay or big bale silage may need to be offered and clean water must be freely available.

Young-stock should be weighed regularly to ensure target growth rates are being achieved.

During the second year of their lives, heifers can be block-grazed, utilising outlying or difficult-to-access fields.

They can also be used as a management tool to clean up grass left in paddocks when the cows are moved on.

This helps to reduce the labour required, and can keep the bunch settled.

Yearlings have large appetites and are capable of achieving good dry matter intakes.

Providing they are not under-fed for long, compensatory growth will be achieved when they are moved to fresh grazing.

While pastures used for young calves need to be of very high quality, grass provided to yearlings can usefully be allowed to become slightly more mature with a slightly higher fibre content to aid the growth of frame and development of gut capacity.

Minimising Disease Problems

Parasites and other disease problems can be an issue for young calves, seriously compromising performance.

Calves should always be given access to clean paddocks by grazing them ahead of other stock and a careful watch should be kept for coccidiosis.

As the calves are turned out early, it is not possible to vaccinate for lungworm.

Regardless of the standard of grazing management, calves will be exposed to a growing challenge from worms.

As soon as coughing or scouring starts, a worming programme should be instigated and maintained on a regular cycle (approximately 4-6 weeks depending on products used) through the remainder of the grazing season.

Young-stock should be adequately protected against lungworm and fluke as well as other internal and external parasites with a health programme developed with veterinary advice.

Managing Fences, Water and Shelter

For ease of management, field and track fences can usefully have an additional electric wire at a lower level to prevent calves from escaping.

It is important to ensure calves can reach into water troughs and are not at risk of falling in.

With small calves it may pay to place a temporary trough of smaller dimensions in their fields and move it with them.

Some field shelter may also be required for smaller calves.

If there are no good hedges or convenient buildings available, shelters can be constructed from big bales covered with sheeting.

The Pd+ Farm Improvement Programme provides practical advice on managing heifer-rearing for the greatest fertility.