Grazing Dairy Cows Eating Soil

In recent weeks we have had telephone reports from practitioners about grazing dairy cows are eating soil.  This behaviour seems to affect multiple cattle that will manically dig at the ground, eat soil, stones and even rip up astroturf cow tracks!  No other clinical signs are reported and cows are otherwise well.

Nine farms have reported these clinical signs from different practices in different areas across Dumfries and Galloway. We have also heard of similar issues in herds in Northern Ireland. In addition, we have had three telephone reports of individual cows with post parturient haemoglobinuria.

We have received blood samples from affected cows and also seen results from practice in house biochemistry testing.  The most consistent biochemical finding has been hypophosphataemia with some cows also exhibiting marginal blood magnesium levels.

Most affected herds are spring, block calving New Zealand style grazing herds.  Grass availability has been reduced because of the dry conditions and in some herds additional silage feeding has been available, although cows were only eating limited amounts.  Parlour concentrates and minerals were available to all cows and water supply was not compromised.  Where available, fresh grass analysis indicated that the grass was very high dry matter (up to 35%), high sugar and low fibre.

In some herds there has been a clinical response to supplementation with extra phosphorus. This has either been given through the water or in the parlour concentrate. In some herds response has been within ten days of supplementation, in others it is taking longer. There have also been some limited rainfall and temperature rises since the first diagnosis.

This is considered a particularly unusual clinical presentation and we do not claim to have all the answers, but some information gleaned from the literature and from discussions with nutritionists and crops and soils colleagues is listed below:

  • It would seem that this presentation is linked to herds maximising the use of grass in prolonged dry conditions rarely seen in SW Scotland
  • The clinical signs of pica have been reported before in similar situations and have been linked to either hypophophataemia, hypomagnesaemia or acidosis and we have some evidence for these conditions
  • Of these, the hypophosphataemia would seem the most consistent finding and likely diagnosis and may also link to the reported cases of post-parturient haemogolbinuria as well
  • The dry weather along with very low overnight temperatures result in very low uptake of phosphate by grass
  • Compared to most other plant nutrients phosphate is not very mobile in the soil. Cold soil conditions make it even less mobile and cold soils in spring can lead to phosphate deficiency in most crops
  • Now that there have been higher temperatures, along with some rain, we are hopeful that there shouldn’t be an issue during the rest of the year

We would be really interested to hear of other reports of this condition and the associated herd histories

Posted by SRUC Veterinary Services on 12/06/2020

Tags: PCHS