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School of Agriculture, Aberdeen, Scotland and , and West Virginia University, Morgantown 26506
Abstract
The utilization 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. Fertilization 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. Fertilization 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, ultrafiltrable 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. Ultrafiltrable Ca in blood was affected by fertilizer and period, but it is questionable whether either ultrafiltrable Mg or Ca would provide a more sensitive index of mineral status than serum concentrations. Concentrations of K, Na and P in saliva were more susceptible to fertilizer and period effects than were concentrations in blood, although all values fell within a normal range. There was no evidence of an inverse relationship between serum Mg and concentration of K in saliva of cows after a change from a winter-type diet to spring herbage containing high levels of N and K.
1 Published with the approval of the Director of the West Virginia Agr. Exp. Sta. as Scientific Paper No. 1642.
2 The authors acknowledge the assistance of Mr. J. Hedges and Ms. Linda Vona in the conduct of the feeding trials and in the analysis of samples, and thank Dr. W. V. Thayne for statistical guidance. They also wish to thank Potash Import and Chemical Corp., New York, for donation of kieserite fertilizer.
3 School of Agriculture, Aberdeen, Scotland.
4 Div. of Anim. and Vet. Sci., West Virginia Univ., Morgantown.
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