Build Grass Cover in Autumn

Building grass cover during August is essential in extending the grazing season. This has benefits form an environmental and animal performance perspective. Extended grazing results in less silage in the diet reducing methane production, while achieving cheaper gains from grazed grass. Where animals have shorter housed periods, less slurry is generated reducing costs and less ammonia emissions from manure storage.Arrabawn Signpost Farmer’s Conor and Vincent O’Brien are Milking 130 cows in Tynagh Co. Galway. With a stocking rate of 3.2 Livestock Units on the milking platform, the O’Brien’s have been building grass cover on the farm since mid-August. The sole purpose of building grass cover at this time of year is to keep grass in the diet for as long as possible, which is generally until mid-November on the O’Brien’s farm. When building grass cover demand is within control; however, growth is highly dependent on weather conditions and land type. Flexibility is required throughout the autumn and the measuring of grass is of upmost importance to know how much grass you have on the farm and how much you need to have in front of cows. If at any stage average farm cover drops below target, corrective action needs to happen quickly. Animals will be required to enter grass covers above 1400kg/DM/ha which is the target for summer months. In managing this the O’Brien’s focus on allocating grass using strip wires to ensure paddock damage is minimised and that residuals of 4 cm are achieved. Recent clover scoring on the O’Brien’s farm showed 37% of the farm having a high clover level, 18% with a medium clover level and 32% with a low clover level. This has aided in decision making around fertiliser application with only 15 units of protected urea applied in mid-August on paddocks with no clover and slurry from the collecting yard targeted to grazed paddocks. This along with bringing silage ground back into the rotation has aided the building of grass cover on the O’Brien’s farm.

Nitrogen Response

Matching Nitrogen (N) application to grass growth optimises the efficiency of N and reduces greenhouse gas emissions. Response to Nitrogen declines as we progress through the autumn. Teagasc Research carried out over a 3-year period at four sites in Wexford, Cork, Louth & Mayo within the Agricultural Catchments show the average response to per kilo of N applied during August, September and October were 27kg, 19kg and 10kg respectively (Figure 1).

Grazing Targets

PastureBase figures for the O’Brien’s Farm currently stand with an average farm cover of 1000kg/DM/ha and a cover per livestock unit of 304. These are good guideline figures to follow for the mid-September period however, regular measurement is required to identify where deficits may occur. Supplementation may be required to fill deficits but keeping grass in the diet should be priority for all farmers at this stage. It is important to note that grazing targets differ depending on stocking rate and land type.


Chemical fertiliser (Nitrogen and Phosphorous) must be spread before the 15th of September.

Slurry must be applied before the 1st of October and ensure slurry tanks are completely empty before the housed period.


In summary cows should be fed using the cheapest feed available, which is grass, while also setting up the farm for spring grazing. Autumn management of grass has a large influence on the supply and quality of grass available for the following spring and so it is vital to get autumn grass management correct. Grass budgeting tools are available to farmers on PastureBase and are useful in keeping the farm on track for the autumn period. Have your fertiliser applied before the 15th of September and make sure slurry tanks are empty by the 1st of October.

Lameness in Dairy Cows

Lameness is a major issue within dairy herds and is the second major cow health concern following closely behind mastitis. 20-35% of herds suffer from some degree of lameness.

Digital Dermatitis or more commonly known as “Mortellaro” is the main cause. A combination of bacteria is picked up by the hoof and an infection sets in on the soft tissue at the heel. The lesion is very painful and can have major knock on effects on the cow. Her feed intake will be reduced along with restricted mobility due to the pain.  The end result for farmers is a decreased milk yield, veterinary bills and dumped milk, extra labour, reduced fertility and reduced net margins. A 20% infection rate in a herd will cost €98/cow. In the average 100 cow herd that is a loss of €9,800 losses on lameness alone. Treatment for Mortellaro often involves antibiotic and pain relief. The bacteria can become highly infectious and easily passed from one cow to another. The cow must be isolated close to the parlour to reduce distance walked and prevent further spread.

Other causes of lameness are sole bruises, sole ulcers, white line disease and laminitis. These are caused from an injury rather than an infection. With 90% of cases affecting hind limbs, generally affecting the outer claw. Walking on rough roadways and wet conditions will weaken the hoof wall. For 30% cases, within the first hour, water is absorbed into the hoof, softening the hoof. Care must be taken in the coming days/week as rain falls, hoofs will absorb the water, while ground remains rough/uneven, possibly causing damage to cow’s feet introducing lameness

Signs to look for: Hunched back, stiff joints, one limb moving slower, short steps, standing with front legs crossed and swinging hind leg out or inwards.

Lameness prevention is very minimal on Irish Farms and usually only begins when there is a problem. Prevention is much better than cure, can be managed through regular foot bathing, clean yards and cubicles and hoof pairing when required.

Also as part of a prevention programme, feeding a mineral supplement, such as the Trace Pak range from Arrabawn, which contains chelated zinc, will help strengthen the hoof wall making the hoof more durable.

Foot Bath : Fill to a depth of 6-8 inches to cover entire hoof and 8-10 feet long. Never leave the volume drop below 5 inches. A top up between milking’s or towards the end of milking. Ensure product chosen works well in organic matter and dirty water. Such as Provita Hoofsure Endurance. In general solutions need to be changed every 200 walk-throughs. Once a week is plenty enough for a non-affected herd as a prevention.

June Fertiliser Application
  1. Adjust N application rates based on growth rates. One unit of N per day of rotation is recommended. Protected Urea can be used during dry conditions. Once soil moisture deficits are restored, nitrogen mineralisation from the soil will occur and 8 – 16 units/ac can be released which will help kick start growth. Spreading excess N will not be used up by the plant.
  2. The following regime should be at the present time; < 25kg DM/ha growth – hold N spreading until weather changes. Growth of 25 – 50 Kg DM/ha – continue to spread reduced N level (15 kg N/ha) and growth of 50 + Kg DM/ha – continue to spread as normal.
  3. Following your soil results or Nutrient Management Plan, applying Phosphorus and Potash where needed. This will help with root recovery, water uptake and grass recovery.
  4. Sulphur is important for Nitrogen update and efficiency. Sulphur aids in plant protein production and grass that has sulphur will remain higher in protein and retain feeding quality later into the season. Include at a rate of 12:1 for grazing.
  5. Paddocks that have a high moisture deficits or are burnt/brown in colour, the advice is to hold off fertiliser application until rain is forecasted.
  6. Palatability may be an issue with the sudden uptake of Nitrogen. Using products with sodium will help increase palatability of the plant.
  7. Good time to apply Lime on bare paddocks. May not get another chance this year. Apply the recommended rate depending on your soil results.
  8. Silage ground for second cut needs to applied as soon as possible if not already done to maximise growth and potential yield. If silage ground is bare consider splitting the application by applying 50% now and the remainder in a few weeks.
  9. Cattle slurry is the best way to replenish the nutrients taken off in the first cut. Apply 2500 gallons to the acre. Again watch out for the weather forecast and apply using a low emission system if possible.
  10. Second cut silage requires 80 units of N, 12 units of P, and 80 units of K and 16 units of S.
Grass Shortage and Cow Performance

With the current dry conditions and reduced growth of grass there is the risk of cows not having enough grass to meet their requirements. Under dry conditions, grass will tend to ‘shoot out’, get stemmy and go to seed, with a dramatic fall off in feed quality. This will be evident in lower milk yield and lower milk solids, especially milk protein and butterfat. Milk protein is directly related to the amount of energy the cow is consuming – low grass / feed intake => low milk protein. That is why it is important to feed the cow as much grass as she can eat and grass with the highest possible energy content (DMD). The typical Friesian cow will consume approx. 18 kg dry matter per day – but often this level of intake is not available to her due to poor grass growth or a low allocation of grass – it is possible that some cows have as little as 12-13 kg dry matter available to them!

We are just over the peak milk yield but if milk yield is declining by more than 2% per week it is a sign that the cow is not eating enough and if milk protein is low also she is not getting enough energy for milk protein production.

  • Fresh grass is likely to be limited in the near future – some farmers are extending the rotation to 30-35 days. This will have implications for daily dry matter and energy intake, so it is crucial that energy and feed intake is maintained to avoid a steep fall off in milk and milk solids production.

So keep an eye on Dry Matter Intake and presume that the cow is only getting about 1/3 her requirements from fresh grass – 6 kg out of 18 kg! How do you make up the difference? There are a number of options involving balanced dairy concentrate, silage, straights and roughage such as straw

  • Concentrates – during this stressful time it might be a good idea to feed 4 – 6 kg dairy nut per day. 16 or 18 % Protein? If the grass is not very leafy go for the higher protein – higher protein will also help stimulate appetite, maximising feed intake.
  • Silage – if you have bales taken from paddocks a few weeks back they might be the best option, not eating into your winter stash. Silage with a reasonable level of stem will also contribute to maintaining butter fat while also promoting good digestion through increased saliva production. 20 kg silage will supply approx. 5 kg dry matter
  • Feeding straights, palm kernel, soya hulls, maize meal, is a good way to fill the void – straights alone are not the answer as they will not be fortified with adequate minerals and vitamins. When choosing straights, it is best to have a variety of ingredients, starch and fibre, based on their digestion rates so that there is an even supply of energy until the next feed. For convenience, straights could be introduced if the diet requires more than 8 kg concentrates in the parlour (4 kg morning and evening).
  • Roughage, such as straw is important, it gives good gut-fill, promotes cud chewing and saliva production which is important for good rumen function. Generally roughage is low in readily available energy, not too much is needed as it may dilute the cow’s energy intake. 1 kg/day. If silage is likely to be limited straw could be fed up to 4 kg /day, with concentrates, to dry cows and replacement heifers.

So when putting a diet together, keep the above in mind and you might consider a mix such as:-

  • 4- 6 kg Dairynuts (16% or 18%) BreederMax 16
  • 4 kg Straights (palm kernel/ soyahulls/ maize meal / rolled barley)
  • 20 kg Silage (5 kg DM)
  • 25 kg Fresh Grass (5 kg DM)

There are reports of cows licking stones etc.  – feeding an adequate amount of balanced ration could remedy the situation as it may be a craving for minerals and/or salt.

It appears that this phenomenon is related to the salt/phosphorus/magnesium complex and is exacerbated by a shortage of feed. So the licking of stones etc. could be the first sign that the cows are underfed, especially with regards to mineral/vitamins. A cow getting 4 kg balance concentrate is unlikely to be very deficient in phosphorus. Likewise, a cow on the recommended diet of dairy cubes, magnesium included, will be getting sufficient magnesium to meet her requirements.

The recent very warm weather will have caused a lot of perspiring with the loss of salt from the cow’s system – making salt licks available may help. Salt is like lime on land, it helps a lot of other things to function properly

  • Salt helps in the regulation and balancing of bodily fluids and electrolytes
  • Salt will supply sodium which is used in the production of saliva for optimum rumen function.

A useful product to have accessible to the cows might be the Trace Pak Fertility/ High Mag block. It contains a full range minerals and vitamins including 3 % phos, sodium (salt) and Magnesium.

Grass fertiliser as a sources of sodium, e.g. Sweetgrass, Sweet 18’s, – Sodium is essential in optimising sugar content, improving palatability and dry matter intakes. In conserved grass,

sugars convert to acids which aid fermentation and preservation.

Sodium plays a key role in optimising mineral balances and reducing the risk of hypomagnesaemia.

After this period of relative grass shortage, there will be a rapid growth of lush leafy grass. This is highly digestible, low fibre grass which will be conducive to Rumen Acidosis (SARA), poor digestion resulting in lower milk solids. It will be important to include a good source of fibre and buffer in the cow’s diet to counteract this – a good indication of any acidosis will be the cows scouring.

Summary: – be careful not to underfeed cows at this time. It will have implications for

  • Milk yield – a steep decline due to low dry matter intake.
  • Milk Quality – low milk solids due to low energy intake
  • Fertility – maintaining pregnancy
  • Make salt/ mineral/ vitamins available to cows, especially during period of warm dry weather.