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Seasonal Targets

The grazing season can be divided into three periods.
spring
summer
autumn/winter

What is the Target Average Cover for your farm?

It is useful to set target average covers at key times throughout the season such as spring turnout, summer or main grazing season and at housing. For the main season a target can be calculated using the simple formula below and modified with local experience of your own farm. Targets can be used as guides to achieve a well balanced grazing system.
Target Cover =
daily herd requirement (kg DM) + [2 X residual cover]
       daily grazing area (ha)                                          
                                               2
e.g. 100 cows @ 5 cow/ha grazing stocking rate
Target Cover (for July)            = [(100cows X 16DMI / 1.0ha) + ( 2 x 1650)] / 2                                   
= ~ 2450 kg DM/ha
NB. Either increasing the daily area grazed or grazing harder will reduce the target average cover.

Spring (February to April)

How do you plan to maximise the amount of grazed grass in the cows diet in spring? How do you decide when to turn out? The latter will depend on grass supply, stocking rate, spring nitrogen, calving pattern and the other enterprises on your farm. A grass budget can be used to meet required targets for cow intake, milk production and grass covers. The grass supply should be monitored weekly during the spring period because of variable grass growth rates.
Early season grazing
Early season grazing

Managing turnout and budgeting early grass:-

  • Plan to turn out some of the herd when you reach target average grass cover of 1900-2000 KG DM/ha. The first paddocks' pre-grazing covers should be around 2500 kg DM/ha and daily grass allowance per cow should not be less than 5 kg/DM/cow/day.
  • Late turnout onto high average cover across the paddocks will lead to poor grass utilisation, poor grass quality in May-June and often unnecessary paddock silage being made!
  • With the help of a grass budget plan to finish the first rotation sometime in the latter half of April - when grass supply balances the herd's grass demand (this date will vary according to location, grass growth and your grazing stocking rate in spring)
  • Practices such as block grazing within paddocks and a good farm lane network are essential to reduce the risk of soil damage during this period.

Summer (May to September)

How do you plan to maximise milk from grass through summer? To achieve consistent herd performance on a virtually grass-only diet demands a consistent supply of high quality grass to the herd. Weekly monitoring of average grass cover and assessing residuals will help. Regularly updating your grass budget will help you to make timely decisions eg adjusting the rotation length and grazing area; introducing supplements and adjusting fertiliser applications.
Ideal pre-grazing cover
Ideal pre-grazing cover 3500KG DM/ha

Managing grazing through the main grazing season:-

  • Average grass cover should be maintained at 2200-2500 KG/DM/ha on the grazing area during the main grazing season (depending on the effective grazing stocking rate, from four to six cows/ha, and herd calving spread).
  • Avoid grazing down to very low residual covers(<1500 KG DM/ha) as this will result in poor grass intakes, reduced milk yields and percent milk protein and will slow down grass regrowth, especially in a dry spell.
  • Maintain your pre-grazing covers at 3300-3600 KG DM/ha. If necessary, top any paddocks with high residual covers (>1800 kg DM/ha). Commence topping, if required, in early (mid May) rather than late season. Aim to maintain the proportion of live-leaf in the sward immediately ahead of the cows at greater than 65 percent green leaf.
  • Use grass cover estimates to identify grass surpluses and deficits across the grazing area and take appropriate action.
  • Aim to build up average cover to 2600-2800 KG DM/ha (depending on stocking rate) by late September and increase rotation length 30 to 35 days (this will require some silage aftermaths to be brought in).
Learn to recognise a grass surplus on your farm, when:-
  • Average grass cover exceeds 2500 KG DM/ha (grazing stocking rate of four to five cow/ha) from late April to August.
  • There is a very steep "wedge" pattern of grass covers(1600-4500) on the grazing area.
Grazing cattle

Learn to recognise a grass deficit, when:-

  • Average grass cover is less than 2000 DM/ha and when pre-grazing yields are less than 2800 KG DM/ha (at grazing stocking rates of four to six cows/ha). Allowing covers to drop down to very low levels will result in reduced grass growth rates across the farm and will depress cow intakes.
  • Low average cover can be alleviated by increasing the grazing area and/or introducing supplements while maintaining rotation length at 20 to 25 days.

Can you adjust the grazing area to grass growth?

At different times of the year more or less grassland will need to be brought into the grazing area as growth and, to a lesser extent, herd demand fluctuate. The required grazing area can be estimated using your herd’s demand for grass and the present or predicted growth rate.
Area Required (Ha)=                                                       Herd demand (KG DM)    
Grass Growth Rate (KG DM/d)                                                                                                 
OR
Grass Growth Rate Required =                                    Herd demand (KG DM)
Area required for Grazing(ha)                                                                                                  
eg 80 March calvers; S.R. = 2.5 c/ha overall; 32 ha farm High Grass System
grazing area required in late May ... =                                80 cows X 17 KG DM =18 Ha
                75 kg/d                                                                                         
grazing area required in September ... =                         80 cows X 12 KG DM =32 Ha  
                 75 kg/d                                                                                   
eg 80 Winter calvers; S.R. = 2.5 c/ha overall; 32 ha farm… High Forage System ie where a greater area is closed off for silage in spring the target grass growth rates must be higher. These can be easily calculated for your farm and then compared with regular paddock cover estimates.
grazing area required in late May ... =                80 cows X 15 KG DM = 86 kg DM/ha/d     
                      14 ha                                                                             
This will dictate the fertiliser rate needed to support the required growth rates.
Autumn/ Winter (October to December)
Can you put autumn grass to good use? You must aim to optimise the amount of grass utilised by the herd through autumn and finish the grazing season close to target closing average cover so as to set the farm up for early spring grazing.
Block grazing cows
Block grazing cows in November

Managing autumn grazing and setting up for spring:-

  • Extend the grazing season by "pushing" the grass supply into October and November. Expand the grazing area and reduce the time spent grazing in accordance with average cover and ground/ weather conditions. Rotation length will increase to 50 days or more.
In the last rotation, the first paddocks should be rested from October 10 to 15 until spring grazing resumes. Avoid pre-grazing covers of greater than 3800 KG DM/ha. Heavy covers will be low quality and often result in poor utilisation by the cows. Furthermore they have a very detrimental effect on the following spring grass growth.
Plan to cease grazing in late November/early December at average cover of 1900-2100 DM/ha, with a range in paddock covers of 1600-2400 kg DM/ha.