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Autumn management mustn't jeopardise minimum grass cover needed for spring

From a straight flush to going bust! Managing grass growth as we transitioned from August to September has been rather like a game of Blackjack. Many farm covers have changed from having massive increases to big losses, depending on where you're farming.

This has been very noticeable on free-draining soils where low rainfall levels have been coupled with a spell of colder weather.

These farmers are facing a challenge of extending the grazing rotation and building up grass cover. Not an ideal scenario if you are likely to go over quota – in this situation you really need to be able to produce milk from grass alone.

When faced with the undesirable, it's important to align decisions with the key priorities of autumn management. We extend the rotation length to extend the grazing season. But the key objective is to leave the farm fit for next season. This means leaving the farm with sufficient good quality pasture for the spring that will maximise grass growth for cows calving down in a condition score of greater than 3 (3.25-3.5 for heifers).

So autumn management must not jeopardise the minimum amount of grass cover required for the spring. In addition, it must avoid poaching, leaving poor residuals or excessively heavy covers that will impair grass growth in spring. Milking or underfeeding certain categories of cows for too long that results in thin in-calf cows is also a no-no.

On top of all these physical targets is the challenge of managing the risk of a super-levy fine on over-quota milk.

To illustrate, consider a 30ha farm milking 96cows at a stocking rate of 3.2LU/ha and currently producing 1.2kg of milk solids per cow per day. Let's say that this farm has 40,000l of quota remaining. When feeding 1kg meal per head the cows require around 15kg grass. So this would equate to a daily grass demand of 1,440kg drymatter (96 cows x 15kg). To work out the demand per hectare, we divide 1,440kg by 30ha to get 48kgDM/ha. In this situation the farm needs a growth rate of greater than 48kgDM/ha/day to increase the grass cover.

Say the farmer aimed to have an average pasture cover of 1,050kgDM/ha by September 30, and hoped to see this accumulate throughout September starting from an average cover of 825kgDM/ha on September 1 (825/3.2=258kgDM/LU). This would have required a grass growth rate of only 7.5kgDM/ha/day above pasture demand over a 30-day period or 55kgDM/ha/day, which is very plausible for the first half of September.

However, the calculation changes if the dry and cold weather resulted in an unexpected fall in pasture cover to 700kgDM/ha by September 15. This would now require a grass growth rate of 23kgDM/ha/day over grass demand to reach the target of 1,050kgDM/ha by September 30. At a demand of 48kgDM/ha/day, this would equate to a grass growth rate of 71kgDM/ha (48+23), which is highly unlikely. Doing nothing, and hoping that it will come right when faced with this set of circumstances is not an option. Effectively, the farm would run very short of pasture as the rotation length would be faster than desired.

So the key decision when you run short of pasture is to slow grazing down, and in this situation I would advise pushing to at least a 40-day rotation, if not 45 days which equates to 0.75ha/day (30ha/40day). With an average cover of 700kgDM/ha this is only going to provide the cows with around 1,050kgDM (700kg x 2 x 0.75ha) of the 1,400kgDM/ha required. This is a deficit of 3.6kgDM/cow. The easiest option in this situation is to increase concentrate feeding from 1kg to 5kg/head.

But this is far from ideal if the available quota is used up by the end of October with nothing remaining for spring milk.

For a farmer in an over quota position, I would say that it's imperative that every litre of additional milk should be produced with no extra variable costs.

But how do you milk on this autumn with no brought-in concentrates if you are short on grass?

The feed deficit can be filled by one of three options:

1. Surplus stocks of conserved forages (ideally high quality round baled silage) or an existing forage crop;

2. Bring in extra ground such as silage ground, either by grazing or zero grazing;

3. Systematically drying cows off and moving stock off the milking platform.

As surplus stocks of fodder are not as common as they were 12 months ago, the use of scanning and milk recording to determine the number of cows to be milked next year, along with a winter feed budget, may be the first step in this process before diving into silage stocks.

Scanning results and milk recording can also help with the strategic drying off of empty cows with high SCC at this stage.

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For example, in this situation 96 cows would require 2-2.5 bales of silage per day to fill the 3.6kgDM deficit per cow.

Alternatively, drying off 23 cows would also reduce this feed deficit by the same amount and require no extra feed per day.

Drying off 23 cows may seem somewhat extreme in September as it is a permanent decision that cannot be reversed if there is a flush in grass growth. However, it would reduce grass demand to 36kgDM/ha/day which should be attainable in September and may allow the cover to increase and reduce exposure to superlevy.

Whatever you do, I would suggest that if you are in a feed deficit make sure that you attain a 45-day rotation, since this rate of pasture use from the beginning of October will close up your grazing platform nicely and help protect next year's pasture cover.

Dr Mary Kinston is a discussion group facilitator and consultant in Co Kerry. Email:

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