Getting cattle out to grass: Farmers will be turning stock out to grass over the next few weeks and hoping for a decent spell of weather to start the grazing season. Aim to turn cattle out when grass covers are adequate. As a guide this is when there is about two weeks supply of grass in front of them. Avoid keeping cattle housed until there is an oversupply of grass as this can quickly lead to more difficult grassland management.
Most of you will by now have sown nitrogen (N) fertiliser on grazing areas and should be seeing the benefits of slurry applied in mid March. Urea fertiliser is the most cost effective form of N and can still be used where there is some grass cover and suitable moist conditions. In areas of low grass cover and drier conditions it is preferable to use other forms of nitrogen.
Protect against Grass Tetany
A major concern after turnout is Grass Tetany (‘staggers’) which is due to magnesium deficiency. The condition mainly affects cows suckling calves and lactating ewes and is often associated with high potash applications from fertiliser and slurry, particularly on soils that are already high in potash. The risk is greatest for animals under stress as a result of unpredictable weather and change of diet at this time of year.
Prevention involves ensuring animals have a daily supply of magnesium. This can be provided by:
Adding magnesium to drinking water while making sure no other sources of water are available.
Dusting magnesium (calcined magnesite) on the grazing pasture.
Treating with magnesium boluses.
Offering a 50:50 mix of calcined magnesite and molasses. Approximately 2.5 kg of the mix provides for 20 cows on a daily basis. Keep the mix stirred and top up regularly.
Magnesium licks or blocks and/or feeding a high magnesium meal daily.
Young growing cattle benefit most from an earlier start to the grazing season and can be turned out when grass covers are lighter (1900-2000 kg dry matter per hectare (7-8 cm in height). Start at a low stocking rate of 1000 kg per hectare.
Suckler cows and calves should be turned out to grass when ground conditions allow and ideally when average grass covers are 2200 kg dry matter per hectare (9 cm).
For most beef and sheep farms, moving stock every three days achieves efficient grass utilisation. This means for a 21 day rotational system, six to seven grazing areas are recommended. To manage grass covers efficiently you need to know how much grass is left on the grazing area on a weekly basis. In the early part of the season this can be achieved by grass measurements and by assessing the grazing days ahead. The grazing days ahead should be within the range of 12-15 days. The stocking level depends on the sward quality, growth rates and soil fertility levels. Table 1 provides a general guide on stocking levels.
Overstocking reduces grass growth and livestock performance. Understocking may maximise livestock performance in the early part of the grass year. However, sward quality quickly deteriorates as the season progresses resulting in poorer utilisation and reduced livestock performance later in the year.