Quote:
In plants, generally the leafy parts are relatively high in calcium and low in phosphorus, whereas the reverse is true of the seeds or grain. Legumes, in general, have a higher calcium content than grasses. As grasses mature, phosphorus is transferred to the seed (grain). Furthermore, the phosphorus content of the plant is influenced markedly by the availability of phosphorus in the soil. Therefore, low-quality pasture devoid of legumes and range plants tends to be naturally low in phosphorus, particularly as the forage matures and the seeds fall.
Sheep subsisting on mature, brown, summer forage and winter range sometimes develop a phosphorus deficiency. Sheep kept on such forages or fed low-quality hay with no grain should be provided a phosphorus supplement (ie, defluorinated rock phosphate) added to a salt-trace mineral mixture. Because most forages have a relatively high calcium content, particularly if there is a mixture of legumes, diets usually meet maintenance requirements for this element. However, when corn silage or other feeds from the cereal grains are fed exclusively, ground limestone should be fed daily at the rate of 0.02–0.03 lb (9–14 g).
Sheep seem to be able to tolerate wide calcium:phosphorus ratios as long as their diets contain more calcium than phosphorus. However, an excess of phosphorus may be conducive to development of urinary calculi or osteodystrophy. A calcium:phosphorus ratio of 1.5:1 is appropriate for feedlot lambs. For pregnant ewes, the diet should contain ≥0.18% and, for lactating ewes, ≥0.27%. A content of 0.2%–0.4% calcium is considered adequate, as long as the ratio is maintained between 1:1 and 2:1.
Ground limestone fed...
