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Analysis of silages shows impact of dismal weather

the extremely wet and poor grass growing conditions over the past summer/ autumn are really showing up in the general poor quality of silage that has been analysed so far this autumn.

Obviously poor fermentation and low dry matters are visible as soon as pits or bales are opened.

Further analysis is showing poor energy levels, low proteins and low pH levels. These factors will not only make formulating balanced rations very difficult this winter but the wet conditions encountered over the past two summers are also posing specific mineral challenges in silage stocks.

Soil compaction resulting from the use of heavy machinery or by intensive stocking density over numerous seasons has many consequences.

As well as reducing grass growth, soils that are heavily compacted are anaerobic in nature as a result of the air being driven out.

Under these soil conditions iron and molybdenum become very soluble and are rapidly sucked up by the plant.

This results in grass silage which is very high in molybdenum, which locks up available copper, reduces cow fertility and results in classic copper deficiency.

These silages may also be very high in iron which not only locks out copper but also zinc and manganese which are essential for hoof health and also fertility.

High levels of iron in silage also creates a big demand for immune antioxidants such as selenium and vitamin E.

These antioxidants are needed to make iron 'safe', with the result that the animal's immune system is effectively compromised. Unless boosted by targeted mineral supplementation this will leave animals more susceptible to health issues and infections.

The second consequence of the wet growing and harvesting conditions is an increase in soil contamination and this is a particular problem with later cut silage that again will become very evident as pits and bales of silages are opened.

Soil contamination will not only reduce palatability but further increases the level of iron and all its negative consequences.

Aluminium levels will increase in this situation which in turn can lock up the available phosphorus that is so essential for energy and growth, particularly in the finishing period.

The final key mineral to focus on this winter is sulphur. As well as being an essential component of microbial protein synthesis, sulphur is also an essential requirement for rumen fungi.

These unique rumen microbes are instrumental in 'drilling' into chewy fibre and opening the way for fibre bacteria to extract as much nutrients as possible from the mature chewy silage that is likely to be around this winter.

Other points of note:

nPhosphorus up by 10-20pc on 2011 levels. This increase came on the back of warm early spring weather and increased soil temperatures;

nPotassium at some of the highest levels for the last four years. These increased levels lead to increased risk of milk fever;

nMolybdenum levels are 30pc higher than 2011 and 35pc higher than 2010. This is an extremely significant increase. As stated earlier, molybdenum is antagonistic to copper availability in cattle. Separate to its depressive effect on copper it will also directly interfere with fertility by depressing oestrus activity. It is essential to tailor dietary copper levels to match forage molybdenum.

nTrace minerals have hugely variable levels when compared with 2011. Iron and manganese are greatly reduced with no major change in zinc or cobalt levels. Erratic grass growth patterns led to these hugely variable levels. However, these changes are not particularly significant in animal health.

Therefore carrying out a detailed mineral check of your forage is essential to ensure that performance, cow health and fertility are not compromised in your herd.

Receiving specialist advice on supplying a correctly balanced mineral supplement to suit the category of stock you are feeding is essential this winter.

There also needs to be an action plan to reduce soil compaction for the next silage season that will improve soil fertility and forage mineral balance.

Gerry Giggins is an animal nutritionist. Email:

Indo Farming