ABSTRACT
Magnesium is a nutrient required for all animals, but it is especially critical for ruminants. Its functions primarily as an enzyme cofactor, it also competes with Ca ++ in excitation secretion coupling processes. Toxicity of magnesium is not known to be practical problem. However, one of the major effects of excess magnesium intake is diarrhea and excessive loss of body fluids. On the other h and, excessive sulfur may overload the urinary excretion system, also interferes with the metabolism of certain other minerals, especially selenium. Acute toxicity resulting from ingestion of large amount of magnesium sulfate causes gastrointestinal irritation, manifested clinically by severe abdominal pain, watery or bloody diarrhea accompanied by severe dehydration, muscle twitching depression of cardiac contractility, lung congestion and respiratory failure of death from anoxia. Owing to frequent and haphazard use of this drug and its side effect, this work was done in an attempt to study further fundamental basis of magnesium sulfate in animals, calves were used to study the effect of prolonged administration of magnesium sulfate on general health condition and some biochemical constituents particularly those related to kidney function, so that oral administration of magnesium sulfate was continued for eight days. The dose was increased gradually. Initial dose [100 g], medium [150 g], higher [200 g], then final doses [250 g/day], respectively. Each dose was repeated for two successive days. The obtained results revealed that the initial dose failed to produce laxative effect at first two days which began to appear at the third and fourth days after administration of 150 g [medium dose]. The higher dose [200 g] produced a purgative effect at fifth and sixth days. Superpurgation, manifested by frequent painful evacuation of bowel which by turn leads to excessive loss of body fluids and biochemical disturbances, was clear at the seventh and eighth days by using 250 gm [final dose]. The excessive loss of body fluids manifested clinically by profuse water diarrhea, sunken eyes, dryness of skin, oral cavity and muzzle as well as severe dehydration, bradycardia and decreases of respiratory rate. Biochemically, significant decrease in the level of both serum sodium, chloride and glucose was observed while levels of total serum protein, creatinine, serum urea nitrogen and potassium were significantly increased. Alteration of serum magnesium level was clear. It could be concluded that, continuous oral administration of magnesium sulfate till overpurgation is contraindicated owing to its dangerous effect on the general health condition, also to avoid frequent body fluids losses, dehydration and renal dysfunction as revealed from clinical symptoms and results of biochemical analysis