Producing quality grass

In spring aim to turn out as early as possible, monitor the average cover regularly, graze more of the farm in the first rotation, be prepared to tolerate some poaching, graze paddocks well to ensure high quality production for the rest of the season, and set the farm up for the second rotation.

In summer aim to maximise the intake of grass whilst achieving the target average cover for the grazing area, adjust rotation length to grass growth rate (by the area used for grazing), and then build up grass cover to feed out through the long autumn rotation.

In autumn as growth slows down try to "push forward" the grass grown in September/October for grazing in November/early December by restricting the area grazed and reducing the hours spent grazing per day. In winter grass covers should be monitored every two to three weeks with a view to turning out early in spring to a target average cover.

A feed budget simply estimates the feed required over a given period of time and compares it with the feed available. It will help you identify any short or long term shortfalls in the feed balance in time for some positive action to occur, such as adjusting the grazing area or fertiliser application. The key element is flexibility - as weather and growth fluctuate and, to a lesser extent herd demand, the budget must be revised.

Two key assessments that impact on the performance in any grazing system are:-

a. Average grass cover
b. Sward quality

Both are closely linked in that if you have the ideal quantity of grass ahead of the cows and each paddock is well grazed, good grass quality will be maintained.

Average grass cover is a measure of the total supply of grass on all the paddocks which are available for grazing. To calculate the average cover you need: i) an accurate farm map with the area of each field: ii) a recent assessment of the amount of grass on each paddock.

i) Farm map

It is essential that you have an accurate farm map of the effective area available for grazing. On many farms it is not the grass cover assessment that is limiting accuracy, but the lack of accurate information on paddock size.

ii) Estimate of grass cover in each paddock

The method adopted at Greenmount Campus is based on platemeter measurements along with visual estimates. You should try to calibrate your own visual assessment by "getting your eye in" with other farmers as part of a Development Group farm walk.

To measure covers you will need a rising plate meter and some recording sheets. Ultimately you need to be able to regularly estimate covers for individual paddocks and across the whole grazing area at key times throughout the year, in order to improve the performance of your grazing system. Does grass growth change on your farm? Of course, and this directly affects the quantity and quality of grass ahead of your cows.

Example: If you estimated the grass cover in a paddock at ~2400 KG DM/ha but the paddock is only 0.8ha, can you calculate the total grass DM in the paddock?

Total DM = paddock size x KG DM/ha.
= 1.3 x 2400
= 3120 KG DM.

To establish the average farm cover do the same calculation for each paddock on the farm and divide through by the total area.(see Table 1)

Table 1 Calculating average grass cover for 10.6 ha grazing.

*using platemeter

Average cover = Total cover / total grazing area
= 24390 / 10.6
= 2300 KG DM/ha

Using the plate meter to estimate the grass cover

Do you regularly assess what grass your cows leave on a paddock? What do you do about it?

It is important to assess post-grazing or residual grass cover as it tell you how well the cows have been fed and it has an effect in the next rotation on sward quality and the speed of regrowth.

Residual cover (KG DM/ha)

Which of the following swards have been well grazed without affecting intakes?

Ideal residual cover 1600 kg DM/ha                                      

Too high residual cover >1800

Residuals for well-fed cows grazing high quality, leafy swards should be 1500-1700 KG DM/ha, ie when a few clumps are left untouched and grazing residual between clumps is low. Residuals will inevitably vary between seasons. In summer with higher dry matter grass and more dead material in the base of the sward, the residual will often be higher than in spring.

b. Sward Quality

Do you assess grass quality ahead of the cows?

The more live, green leaf down through the sward the better the digestibility (D value) and feed quality will be. There is a strong correlation between the sward quality and its milk production potential. Furthermore the previous grazing residual, rotation length, ryegrass proportion, presence of clover and frequency of grass topping will all affect this.

75 D value grass

67 D value grass

Aim for at least 65 percent of live leaf in the sward to maintain high grass digestibility. Where paddocks are grazed tightly in spring, stem development is controlled and this promotes vigorous growth in mid and late season.(Table 2)

Table 2 Effect of spring grazing severity on sward quality and milk yields in August