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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #89024
Title: USE OF AN EXPERIMENTAL HIGH-MAGNESIUM TALL FESCUE TO REDUCE GRASS TETANY IN CATTLE

Author
item CRAWFORD, R. - UNIVERSITY OF MISSOURI
item MASSIE, M. - UNIVERSITY OF MISSOURI
item SLEPER, D. - UNIVERSITY OF MISSOURI
item Mayland, Henry

Submitted to: Journal of Production Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Grass tetany is a non-infectious, complex magnesium (Mg) deficiency of ruminants grazing cool season grasses around the world. It causes an estimated $150 million death loss annually in the U.S. Losses are partially reduced by fertilization, liming acid soils and animal supplementation. Added benefits might be realized by grazing plants containing higher Mg concentrations. HiMag and four other tall fescues were planted in southwestern Missouri and forage mineral levels and grazing animal blood sera and weight gains were monitored over five grazing periods. HiMag contained more Mg than other cultivars and animals grazing HiMag had equal or greater weight gains and had equal or greater blood sera Mg. Environmental conditions did not produce stressful conditions leading to signs of grass tetany in these animals. The Mg in HiMag is available to cattle and would likely provide some protection when cattle are nutritionally stressed for Mg.

Technical Abstract: Grass tetany (hypomagnesemia) continues to be a problem for the livestock industry. An experimental cultivar of tall fescue (Festuca arundinacea Shreb.) selected for high magnesium concentration, HiMag, was compared agai four other cultivars for its ability to reduce the risk of grass tetany. Forage from HiMag contained 22% higher Mg, 18.5% higher Ca, and 9% higher P Pcompared to other cultivars; K levels were not different. Regardless of cultivar, Ca and Mg were lower while K and P were higher during the spring compared to the fall season. The tetany ratio [K/(Ca + Mg) on Moles (+) basis] was lower for HiMag than for other cultivars (1.34 vs 1.65); all cultivars had a higher ratio during spring than fall (1.91 vs 1.31). Blood sera from steers (Bos taurus) grazing HiMag contained 8% higher Mg in fall 1993 but were not different in spring 1994. Blood serum Mg was not differe for cows (either dry or nursing calves) during fall grazing, but approached dsignificance (P=0.09) during the spring 1995 calving season (2.32 vs 2.07 mg/dL for HiMag vs. other cultivars). Animal weight gains were not affecte by cultivar. Normal forage Mg concentrations (>0.20%) and tetany ratios be 2.2 for all cultivars in every season except spring 1995 may explain the la of consistent animal response. No clinical symptoms of grass tetany were observed at any time during these studies. However, the higher Mg concentration and lower tetany ratio suggest that HiMag could provide a mea of reducing the incidence of grass tetany in livestock during periods when risk of the disorder is high.