Equine Science Update
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Pasture mineral supplements needed.
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Mineral levels in pasture may be insufficient to supply the requirements of growing foals according to work presented at the recent equine nutrition conference in Hannover. Louise Jones described the findings of an investigation carried out in the UK with colleagues at Dodson and Horrell . They assessed the mineral content of pastures in areas where foals were commonly reared and compared the differences between spring and summer pasture.

Adequate mineral intake is especially important for growing animals. The mineral content of pasture is affected by factors such as the underlying soil type, species of grasses in the pasture, and whether fertiliser has been used.

The investigators found that overall there was a wide variation in mineral content. Some pasture samples contained minerals levels that would not meet the requirements of fast growing 6 month old horses. (NRC minimum requirements)

They also noticed variation between pasture at different times of the year. Spring (March to June) and summer ( July to September) pastures differed significantly in their mineral content. Summer pasture had lower levels of potassium, copper, zinc and phosphorus. And spring pasture had lower calcium levels compared with summer pasture.

Several factors might be responsible for the higher calcium levels found in the summer. Clover, with relatively high calcium content, is more abundant in the summer. Perhaps the most significant factor was that half of the summer samples were collected in the Newmarket area, where the underlying soil has a high calcium content.

At top end of range all major minerals were present in excess of requirements. However, some samples had levels of calcium, phosphorus and potassium that were so low that they would not supply the minimum requirements for growing horses. The investigators advise that foals should be fed a supplement to ensure they receive adequate minerals if they are reared on pasture.

The range of mineral levels published for cattle pasture (especially calcium, phosphorus, copper, and zinc) do not accurately describe pasture used for horses. Jones suggests that further investigation is needed to assess the various factors that influence the mineral content of pasture used for grazing growing horses.

Further reading.

The mineral content of spring and summer pasture grazed by young growing Thoroughbred in the UK. Louise Jones, Jennifer Lax, Teresa Hollands.Proceedings Equine Nutrition Conference. Pferdeheilkunde (2005) 21, 21 - 23..
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