Grazing Kikuyu

Oxalate chemicals are contained in the leaves of rapidly growing tropical grasses. One common grass we have in NZ is Kikuyu. Originally introduced from South Africa due to its drought tolerance and it has spread widely. 

When consumed by horses, oxalates bind to calcium extracted from feeds or supplements during digestion in the small intestine. These oxalates form a calcium-oxalate complex which is not digested, normally up 90%, in the small intestine by enzymes. The complex then carries the calcium into the large intestine where it is liberated during microbial digestion. The calcium-oxalate complex is not digested resulting in inadequate calcium being absorbed to maintain blood levels for muscle and tissue function.

The importance of calcium in the diet of horses and ponies is crucial. When coupled with phosphorus, the two minerals compose up to 70% of the total mineral content in the body. Calcium is necessary for skeletal, cardiac, and smooth muscle function, nerve conduction, and a host of other metabolic reactions.

Oxalates are most detrimental to weanlings, yearlings, and lactating mares because of the substantial calcium requirements of these horses. Furthermore, these horses usually need considerably more feed than their adult sedentary counterparts, so the quantity of oxalates ingested will likely be greater. Proper skeletal growth of young horses is impossible in the face of calcium deficiency. Similarly, lactating mares fed oxalate-rich forages will produce calcium-deficient milk for their foals, which may contribute to developmental orthopedic problems.

Ensuring calcium intake is greater than the oxalate level in pasture is essential, and horse owners should also be aware that this substance can impede proper absorption of calcium. 

Forms such as Dolomite is not a suitable form to feed to horses due to its lack of bio-availability. Bio-available chelated forms are the safest option. Duwell Compete N Grow contains chelated Calcium and Magnesium in a balanced ration with phosphorus and vitamin D. Boron is also added for extra absorption.   

Another point of caution with Kikuyu grass can also spike in potassium, bind up other important minerals and so coupled with the oxalate issues care should be taken with this grass. Ideally reduce access, increase hay feeding and supplement with good levels of a balanced minerals, vitamins and plain salt.