Our recent sheep article discussed the option of creep feeding lambs to increase lamb performance and its targeted use in overcoming a grass deficit.

Grass supplies are improving quickly on marginal lands but for many flock owners – especially those at high stocking rates – grass supplies are still running behind demand. The situation is very different on farms with better grass growth potential. Swards have responded well to fertilizer with a rise in temperatures leading to grass growth rates matching or exceeding typical rates for the time of year.

Farmers measuring weekly grass growth have recorded growth rates of 30kg dry matter (DM) per hectare (ha) to over 60kg DM/ha on their better performing swards in the last week with swards that were already grazed, rested for a few weeks and recently fertilized performing best. For others with a high percentage of permanent pasture and on poorer soils, growth rates range from 20kg DM/ha to 30kg DM/ha.

Meeting demand

Quoting growth rate in kilogrammes of dry matter per hectare may not mean much to farmers not accustomed to measuring grass growth in this manner.

To put a growth rate of 30kg DM/ha into context, a ewe and her twin suckling lambs in week five of lactation and offered a plentiful supply of grass (5m+), will consume 3.8kg grass DM/day.

Therefore, a hectare of grass growing at 30kg DM/day will provide sufficient grass growth for about eight ewes per hectare or just over three ewes per acre.

This does not consider the grass already available in the field and calculates solely on growth versus daily demand. Table 1 details the daily grass intake requirement for lactating ewes from week one post-lambing up until weaning. As can be seen, a twin suckling ewe’s grass requirement increases until week seven of lactation and follows a declining path thereafter.

However, grass demand remains constant as daily grass intake of lambs increases by about 0.1kg DM per week. Demand will therefore remain constant above 4.4kg DM/ha from week seven onwards.

Influencing performance

Daily intake will be influenced by grass supply and quality. This, in turn, will have a significant impact on lamb performance.

Providing highly digestible grass is generally not difficult early in the season, with lower volumes of grass present and spring growth of very high quality.

Having a sufficient supply of grass is usually the greater concern. Weather will also have an influence, with dry matter in grass significantly higher during weather similar to that experienced in recent weeks.

In prolonged wet periods, ewes will need to consume higher volumes of grass to sustain their required intake requirement.

Difficulties in maintaining grass quality normally materialise as the season progresses with growth rates peaking in May and June and often leading to an oversupply of grass.

If management practices are not put in place to maintain grass quality, lamb growth rates can quickly suffer.

This is of greatest concern as lambs approach weaning with lamb growth rate at this stage influenced primarily by grass intake as opposed to milk yield.

Grazing management

The aim with grassland management is to match grass supply and quality to demand.

As the season progresses, maintaining a high quality sward will be determined by grazing management with the key aim of preventing a build-up of poorer quality grass at the base of the sward.

This will be easiest to achieve with a rotational grazing system that ensures swards are grazed out quickly and managed to promote a high leaf to stem ratio in re-growths.

Even with high levels of management, it will be difficult to keep swards grazed to 3.5cm to 4cm (in the absence of topping) as the season progresses and, therefore, recommended pre- and post-grazing heights will increase.

Table 2 details recommended post-grazing sward heights as formulated from Teagasc research. Post-grazing heights will influence recommended pre-grazing heights (which should not exceed 10cm to 11cm).

Rotational grazing

The two most straightforward ways of implementing a rotational grazing system are to increase group size or split larger fields into a number of divisions that better suit the size of the group.

The latter can be permanent or temporary, depending on the layout of the farm or future plans. Temporary divisions can be implemented even where the farm is fragmented and can be put in place at a relatively low cost.

For the past two seasons, the Athenry demo flock has operated a system of temporarily splitting larger paddocks as grass growth increases.

This was carried out through a mixture of electrified, netted fencing and three strands of electrified wire. It serves in providing highly digestible grass for grazing but also allows surplus grass to be saved as baled silage.

A high percentage of last winter’s silage allocation was saved in this manner with bales harvested from surplus grass in May recording a dry matter digestibility (DMD) in excess of 70DMD. A similar system has also been implemented on farms participating in the Teagasc BETTER Farm sheep programme.

Fertilizer use

Targeted use of fertilizer will also help in boosting grass quality. It is clear to see the benefits of this early in the season with fertilizer use more likely to be concentrated on improving grass supplies rather than focusing on grass quality. As the grazing season progresses, applying even a small allocation of 10kg to 15kg nitrogen per hectare will help to maintain grass quality.

Monitoring of soil sample results analysed in recent years shows continued deterioration in fertility levels with phosphorus, potassium and pH all on a declining trend. As such, there will be a benefit in applying a compound rather than a straight nitrogen fertilizer.

TAMS approvals

Quick approvals from the Department of Agriculture on the final tranche of the TAMS sheep fencing and handling equipment scheme would greatly aid in improving infrastructure on farms.

There are currently high levels of confidence and positivity in the sector following an improvement in lamb price this spring and higher lamb crops. Delaying approvals until later in the season will be a missed opportunity to get developments started and the benefits in terms of reduced labour to be realised.