Breed differences in plasma calcium, phosphorus and magnesium concentrations of Merino, Dohne Merino and S.A. Mutton Merino sheep with relation to the bent-leg syndrome.

Plasma calcium, phosphorus and magnesium concentrations were determined in ewes and their single and twin lambs from birth for 120 days in Merino, Dohne Merino and South African Mutton Merino sheep. Mineral concentrations as well as the plasma calcium: phosphorus ratio were compared between breeds. Throughout the experimental period, plasma calcium and phosphorus concentrations were higher in both single and twin lambs than in the ewes of all 3 breeds. No breed differences in plasma calcium concentrations were found. Animals of the S.A. Mutton Merino breed had significantly higher (P less than 0.05) plasma phosphorus concentrations than the other 2 breeds. The plasma Ca:P ratio in the Merino and Dohne Merino ram lambs was approximately 1.1:1 and in the S.A. Mutton Merino 0.9:1. This converse plasma Ca:P ratio found in both the S.A. Mutton Merino ewes and lambs is believed to result in an induced plasma ionised calcium deficiency which leads to improper calcification of bone. This is believed to be a contributing factor in the bent-leg syndrome. No difference was recorded in body mass between ram lambs suffering from the bent-leg syndrome and unaffected ram lambs. Plasma magnesium concentrations were not affected by breed or age of the animals.