title: Efficacy of a large magnesium alloy rumen bolus in the prevention of hypomagnesemic tetany in cows.
abstract: Two cow-calf grazing studies and 2 rate-of-disappearance trials in steers surgically prepared with rumen fistula were conducted to evaluate the efficacy of a large Mg alloy rumen bolus in preventing hypomagnesemic tetany (grass tetany). The mineral composition of the forage and results of study of 2 cows in the cow-calf studies indicated that an environment conducive to the occurrence of grass tetany existed. Grass tetany occurred in a cow that was given a Mg bolus and in a control cow. Administration of 1 or 2 mg boluses did not affect blood serum Mg, Ca, P, and K concentrations. Bolus treatment did not affect cow-calf performance or conception rate. The rate of weight loss of the boluses in the surgically prepared steers (rumen fistula) ranged from 0.71 to 1.43 g/day or 0.66 to 1.33 g of Mg/day. Steer differences affected the rates of disappearance patterns of the boluses. The rate of disappearance was relatively constant over a 175-day period and regurgitation or passage was not a problem. Although administration of the boluses could have prevented tetany in some animals (borderline), the rate of Mg release appears too slow to be highly effective in preventing grass tetany.
mesh_terms: D000497:Alloys / Q000008:administration & dosage / Q000627:therapeutic use; D000821:Animal Feed; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D005260:Female; D007774:Lactation / Q000187:drug effects; D008274:Magnesium / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use; D008275:Magnesium Deficiency / Q000150:complications / Q000517:prevention & control / Q000662:veterinary*; D011247:Pregnancy; D012417:Rumen / Q000378:metabolism; D013746:Tetany / Q000209:etiology / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D000497:Alloys; D008274:Magnesium