Comparison of fresh grass samples and soil samples to determine its effect on Pica cases at Nantglas Dairy demonstration site.

During the spring and early summer this year, Nantglas cows were yet again eating stones and rubble, known as Pica. This is an ongoing issue for Iwan Francis, having previously lost cows to blocked stomachs, therefore a decision was made to investigate further.

Nigel Howells (Nigel Howells Consultancy Ltd) is one of two consultants working with Iwan to improve forage management, with Nigel specialising on grass and soil management. He advised to take detailed soil samples and fresh grass samples from two fields to compare; one field at Nantglas (a) and one at neighbouring rented land (b). 

The nutritional grass quality on both grass samples for protein/D value and energy were good.

  • 80+ D value
  • ME at 12.5MJ/kg or more
  • Protein ranged between 15-16.5%
  • Sugars were high at 26-28%

Mineral and trace element analysis was carried out on the fresh grass samples to determine what nutrition was readily available to the cows when grazing. 

Historically, Pica is assumed to be linked with phosphorus deficiency, however in this case, magnesium was the antagonist. In both samples, magnesium levels were very low, along with low levels of most major trace elements including copper, zinc, selenium and cobalt. This low magnesium result corresponds with other mineral grass analysis Nigel has done on other farms, also suffering with Pica this year.

With these results, soil samples from the same fields were taken and analysed to determine a correlation between the available nutrients and minerals in the fresh grass samples and the residual availability in the soil.

It could be seen that magnesium and phosphorous where adequate at indices of 2 but, for the soil to work at its most productive, ideally both levels should be slightly higher at 3.

Residual calcium levels were adequate in field a and low in field b. 

Sample b showed low residual calcium level in the soil but had a high available calcium level in the fresh grass sample. Whether this is a true result can only be backed up by taking another sample.

Both soil samples had a high residual level of sulphur which may be as a result of the levels of organic matter. This may need to be considered when fertiliser type is used as a lot of fertilisers contain a sulphur element.

The levels of calcium and magnesium in the soils should be looked at to improve the soil activity in optimising available minerals. An imbalance of low magnesium and high calcium can lead to less availability of minerals and trace elements to the stock. The ideal balance in the soil for calcium to magnesium is 7:1. Whereas with these results, the level is closer to 15:1. A possible short term consideration is to discuss trace element supplements with the farm vet to balance out any current deficiencies in the soil/grass until the correct balance of minerals is available from grass.

In conclusion, monitoring the available nutrients and minerals in the diet will continue and fresh grass samples will be taken next spring when growth is at its peak (after the first rotation has been finished and into the second rotation in mid/late April to early May).