M I N E R a L Status of Beef Cows a N D Sheep on Spring Pasture

The uti l ization of minerals in orchardgrass (Dactylis glomerata L.) fertilized with kieserite (2,240 kg/ha) was examined in spring with lactating beef cows and wether lambs. Kieserite increased the concentration of Mg in vegetative herbage from .22 to .29% (P<.01) and of S from .20 to .29% (P<.01), with little effect on other minerals. Fert i l ization also increased (P<.01) apparent absorptions of Mg and S by lambs fed cut orchardgrass, from 24.5 to 36.5% and from 58.6 to 66.9%, respectively, and increased (P<.01) apparent Mg retention from +.16 to +.33 g/day. Fertil ization did not affect dry matter digestibility or apparent absorption of N, Ca or P by lambs. Composition of blood and saliva of beef cows grazing fertilized and unfertilized pastures was determined during a 2-week period in early spring. Cows grazing kieserite-treated pastures showed a small increase (P>.05) in serum Mg, ultrafihrable Mg and red blood cell (RBC) Mg, and fewer cows on the fertilized pastures showed severe hypomagnesemia (<1.0 mg/100 ml) after the first day of grazing. The decline in blood Mg concentrations was not accompanied by hypocalcemia or by changes in serum Na or K concentrations, but serum inorganic P decreased (P<.01) markedly during the first 10 days of grazing. Uhrafiltrable Ca in blood was affected by fertilizer and period, but it is questionable