Getting more from grass in 2011

While grazed grass, the cheapest feed available, has the potential to support daily milk yields of 25 to 28 litres per cow per day in April/May, many herds struggle to achieve this level of performance. However, in view of the significant increase in the price of concentrates, which looks set to continue in the immediate future, optimising the use of grazed grass in the diet of dairy cows should be a key target during 2011. In addition, as fertiliser prices look set to be approximately £100 per t higher than during 2010, it is critical that grass which is grown is utilised efficiently. This article examines a number of key measurements and targets, which if achieved, will allow you to make better use of one of the most valuable resources on your farm.

1. First grazing rotation target

A key target on most farms should be to have the core grazing area grazed by mid to late April. This will allow a grass wedge to be established, thus avoiding having too many fields at the optimal stage for grazing at the same time. Failing to finish the first rotation on target will mean that as grass growth hits its annual peak, it will be very difficult to achieve target pre-grazing and post-grazing grass covers. Grazing high covers of poor quality grass in early May will compromise herbage quality into mid and late season.

2. Grass cover targets

The target should be to graze swards whenever the yield of grass is 3,000 – 3,300 KG dry matter per hectare, or whenever it comes approximately ? of the way up your wellington boot. Swards should be grazed to achieve a post-grazing cover of 1,600 – 1,800 KG dry matter per hectare. If these targets are achieved the sward being grazed will be mainly leaf (little stem) and post-grazing the sward is likely to be ‘greener’ at the base, allowing for a quick regrowth.

3. Grazing rotation length targets

Controlling the length of the grazing rotation is a useful tool to help control grass supply within the grazing area. A rotation length of 18 - 21 days will normally be required during the period of peak growth in early May, with this normally being extended to 24 - 26 days in July/August and 26 - 30 plus days by September.

4. Grazing stocking rate target

Establishing stocking rate targets is an essential component of managing dairy cow grazing. The optimum early season stocking rate will be influenced by a number of factors including stage of lactation, meal feeding and potential grass growth. Although five cows per hectare maybe the target on many farms for April/May, stocking rates may be increased to six or seven cows per hectare when concentrate feed levels are between 4 and 8 KG per cow per day, or when additional silage is being fed. Failing to reduce the grazing area in situations where high levels of supplements are being fed will ultimately result in an oversupply of grass, and make managing the grazing area very difficult.

5. Measuring grass demand

Identifying the herds grass demand is an integral part of grass budgeting. The daily grass demand on a farm can be calculated by multiplying the number of cows grazing by their estimated grass intake, and by dividing this value by the area being grazed. For example, 100 cows with an average daily grass intake of 16 KG DM per cow, and grazing 25 hectares will have a grass demand of 64 KG DM per ha per day. Grass demand can be increased or decreased in response to changes in grass growth to minimise grass surpluses or deficits. For example, the herds daily grass demand can be reduced through an increase in the area being grazed or by feeding supplements to the cows.

6. Measuring grass growth

Maintaining an awareness of grass growth is critical, particularly in early season, as this allows timely and confident grassland management decisions to be made. The GrassCheck project provides a weekly update on actual grass growth rates at six locations across Northern Ireland, together with a prediction of grass growth for the following two weeks. While this information can be extremely useful in providing information on current and future growth rates at a regional level, a more accurate picture of actual grass growth rates on your own farm can be obtained by walking all the grazing paddocks on a weekly basis, and comparing one weeks data to that measured the week previously. Using a computer spreadsheet, this information can be presented in the form of a ‘Grass wedge,’ which will clearly highlight the extent of grass surpluses or deficits within the grazing platform.

Regardless of how growth rates are measured, it is important to react quickly to a potential surplus or deficit in grass supply. Ideally surplus paddocks should be cut immediately to maintain their position in the grazing cycle, allowing them to be grazed next time round. However, delaying cutting could cause the paddock to fall out of ‘sequence’, and as recovery will be much slower following the harvest of a heavier crop of grass, the surplus situation could easily become a deficit in the next rotation.

Summary

Achieving these grassland management targets and measuring grass demand and growth will require a weekly input of time, perhaps even twice weekly during periods of rapid increases/decreases in growth. However, the ability to produce high yields of high quality pasture and also achieve high levels of herbage utilisation will provide an excellent return on this time through improved cow performance, reduced requirements for supplements and an improved response to fertiliser nitrogen. Therefore, increasing herbage utilisation efficiency should be a key focus during the 2011 grass growing season.

by Dr Andrew Dale, Agri-Food and Biosciences Institute, Hillsborough


Target pre- and post-grazing sward covers

Andrew Dale and Michael Wills assessing grass cover and ground conditions in paddocks being grazed in early March at AFBI Hillsborough