Laminitis: the most common problem caused by UK pasture, mainly due to former cattle pasture dense in high-calorie rye grass and lush, rapid-growing grass on overfertile soil.
Mineral deficiencies: rare in the UK, but some trace elements (for example, copper, iodine, selenium, magnesium, cobalt) can be lost either from leaching in overdraining soils or incorrect management of heavy soils (overliming). Copper deficiency shows symptoms very similar to Cushing’s disease. Mineral deficiencies are associated with bone development problems in foals, nervous system issues, and horses in hard training may have performance impaired by slight imbalances.
Mud fever: typical of south-east England clay soils, which are poor draining and acidic, but also in very peaty areas. The bacteria responsible are acid-loving and live in waterlogged soil.
Hoof infections: more common where pasture is on underlying clay than in sandy, chalky or limestone areas. Constantly wet hooves become soft and more easily damaged. Muddy ground with flints or small stones is the most dangerous, since the flints penetrate the hoof and allow infection to enter.
Thyroid problems: associated with low levels of iodine, can be recognised by “goitre” swelling on the neck. Occurs in free-draining areas but can also be due to over-liming of pasture.
Azoturia: very rich, low-lying pasture prone to rapid growth, high in carbohydrate, can cause azoturia cramps even in grass-kept animals.
For the full feature on making the most of your grazing, see the current issue of Horse & Hound (5 May, 2011)