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Cathal Irwin November/December 2023



  • The silage results are in…
  • Management of young bulls in November


  • How did the farm perform in 2023?
  • Getting heavy covers grazed off


In order , to make improvements in the quality of the silage, Cathal reseeded the main silage field. The field had a high percentage of weeds and docks and the ryegrass was disappearing. This year, he fertilised the silage group in the first week of April to target an earlier cutting date in May. Despite a wet enough May , Cathal got a window of a few dry days and got the silage made. He tested this silage in mid –October and below are the results.

Cathal will judge the silage based on the following parameters;

Dry matter %

The quantity of material left in a feed after the water has been removed by drying. The value is corrected to allow for losses of volatile but nutrionally valulable nutrients during drying, e.g volatile fatty acids 

Low dry matter silages tend to extensively fermented wan will be high in acids and low in rumen structure, reducing intakes. High dry matter silages are more suceptible to spoilage (bacterial and fungal)


25 -35%
pH A meaure of the acidity or alkalinity of the silage; pH<7= Acidic, pH 7= Neutral, pH>7 = Alkaline. Where the pH of grass is above this range, typically as a result of poor or secondary fermentation, underdesirable VFA's may have been formed and production may be reduced. Feeding more acidic silages may impair rumen performance, resulting in acidosis, lower intakes and production. 3.5 -5.0 (depending on DM)
Ammonia High values are indicative of butyric fermentation and may be associated with high blood and milk urea levels; high blood urea has been directly and indirectly linked to infertility. Care should be take in interpreting this term as it is a percent of total N and not a percent of the dry matter. <15% of Total N
Protein If high, additional protein tends to be rapidly degradable and may be poorly utilised, especially if there is inadequate rumen available energy in the diet. High blood and blood urea levels have been associated with feeding this type of silage; the latter can have a direct and indirect impact on fertility.  7-20% DM
Metabolisable Energy (ME) The most important measure of the energy content of silage when fed to ruminants, represtenting the amount of energy available to the animal after accounting for losses in digestion, gases and urine.  8.0 -12.0 MJ/Kg DM
Ash Indicates the mineral content of silage. A high value (>10%DM) may indicate soil contamination, which will reduce intake and is likely to have resulted in a silage with poorer fermentation qualities, such as high acetic and butyric acids and ammonia. High ash conten in legume silages is normal due to their higher mineral content.  <8%DM
Dry Matter Digestibility (DMD) DMD is the content of digestible organic matter in the DM. It decreases progressively as the forage matures and becomes more "stemmy". It is a good guide to the overal nutritive value.

55 -75% DM (depending on the type of stock to be fed)

Lactic Acid Give an indication of the quality of the forage fermentation, being produced almost exclusively by the lactobacilli responsible for good silage fermentation and effective preservation. Grass silages typically have lactic acid contents of 60- 150g/kg, higher values suggesting more rapid fermentations, better protein preservation and less likelihood of other, undesirable by products.

80- 120g/kg DM

Volatile Fatty Acids (VFA's) Will be high when there is a poor fermentation. The undesirable VFA's are butyric and to a lesser extent acetic acid. These are associated with high total VFA's and give a distinctive and persisting smell to badly made silage.

Range: 10 -90/kg DM (keep as low as possible)

Acid Detergent Is a meaure of the cellulose, lignin and lignified nitrogen (heat damaged protein) content of the silage. It can be used to esitmate digestibility. 

300g/kg DM

In summary , Cathal’s  silage is very good . Ideally he would like the dry matter to be close to 25 per cent but it was cut in a window when the weather was wet. This silage will be targeted to the growing stock over the winter  ie weanling bulls and heifers and to cows post-calving in late January and February. This silage will not be fed to cows pre-calving as they will be in excellent condition coming in off grass and Cathal does not wants the cows getting too fat pre-calving. He has second cut silage kept for dry suckler cows which will maintain their body condition.

Making this type of top quality silage will save Cathal money. Eg his weanling heifers will need no meal to gain the target of 0.6kgs weight gain per day. If the silage was below 70%DMD, he would need to feed 1.5 to 2 kgs of meal/head/day to gain the same 0.6kgs liveweight per day.  Cathal has 14 weanling heifers. So 2 kgs of meal x 14 = 28kgs of meal per day saved.


Management of Young Bulls

Picture: The bulls will be getting 6kgs of meal/day until Christmas

The bulls are also getting the top quality silage ad-lib. They are fully dosed and vaccinated. When the remainder of the suckler herd is housed , he will move the bulls to a straw bedded lean – to . The bulls are performing very well , gaining 1.49kgs/day at the last weighing. On October 1st the average weight was 400 kgs . Cathal will weigh the bulls again in November to track their performance.




From a grassland point of view , 2023 could be described as a challenge , largely due to weather. Spring was late, June was very dry and then the rest of the year was relatively wet. While grass growth was  normal, poor ground conditions was  the main  issue on most farm in the west of Ireland.

As Cathal is using pasture base, he can generate a farm summary report which highlights how the farm performed from a grass point of view.

The main points from the report are;

  • Cathal made 33 recordings on Pasturebase which was excellent
  • The farm grew 10.3 ton/DM of grass to date which is very good and is well above the average drystock farm.
  • Overall the grass grown on the farm evenly matched the demand from the herd ie 46kgs/DM/ha grown v demand at 42kgs/DM/ha


The main points from the second part of the report are;

  • Cathal spread 85 units of N/acre to grow the 10.3ton of grass DM/ha (grazing + silage)
  • Grazing started on the 27th of February
  • The good weather in June suited the farm where the peak growth was recorded at 114kgs DM/ha.

Cathal has a closing measure to input which will give a closing cover. During October there was a lot of grass and the very wet spell towards the end of October will mean the closing cover will be above the target of 500kgs/DM/ha .  This is outside Cathal’s  control and will be hoping for a dry February and March to target an early turnout.

Picture Cathal achieved over 220 days at grass in 2023