Effect of dietary phosphorus and roughage levels on calcium, magnesium and potassium utilization by sheep.

Three levels of dietary P (.12%, .24% and .48% of dry matter) and three levels of roughage as ground corn cobs (25% 50% and 75% of dry matter) were fed in a 3 X 3 factorial metabolism trial, utilizing 36 crossbred (Hampshire X Columbia) intact male lambs, 6 to 9 mo of age. All diets contained cane molasses (5%), blood meal (13.5%), urea (1%), corn oil (1%) and salt (.5%). Limestone supplied supplemental Ca and treatment P levels were supplied by monosodium phosphate. Equal levels of corn starch and cerelose supplied the remainder of the diet. The diet was fed ad libitum, once daily. The highest P level (.48% P) resulted in a negative (P less than .01) Ca balance (-.23 g/d vs .12 g/d for .12% P and .31 g/d for .24% P groups), and apparent digestibility (P less than .01) of Ca (1.65% vs 17.18 and 22.2% for the two respective lower P dietary levels). Blood serum concentrations of Ca and Mg decreased (P less than .01) as dietary P level was increased. Apparent digestibility of Mg was decreased (P less than .05) by the highest P level (6.9% vs 21.58% and 18.80% for the two lower levels of dietary P). Level of roughage had no effect on Ca and Mg utilization; however, the highest level (75% corn cobs) resulted in improved (P less than .05) K balance (.85 g/d vs .30 and .50 g/d for the two lower levels of roughage).(ABSTRACT TRUNCATED AT 250 WORDS)