The inability of horses to absorb calcium from calcium oxalate

Abstract
SUMMARY: Six horses were fed Setaria sphacelata var. sericea cv. Narok hay in a mineral balance experiment and were in negative calcium balance. This should have ensured maximum efficiency of calcium absorption. Only 6·3% of calcium from a single dose of 1·32 kg calcium oxalate was retained by the horses, which supports the suggestion that horses cannot utilize calcium in tropical grasses if it is present as calcium oxalate crystals.