Magnesium – Seventy percent of the total body magnesium is found in bone . It also plays a role in muscle contraction , energy metabolism , and calcium metabolism . 5 Serum levels are not under close hormonal control , but vary with dietary intake and renal excretion . Requirements for magnesium are highest in lactating animals . The availability is lower in forages than grains . Multiple factors affect absorption including serum calcium and rumen pH . Serum magnesium levels depend on constant dietary absorption . Magnesium is primarily absorbed in the rumen , and efficiency of absorption tends to decrease with age in ruminants . Clinical signs of hypomagnesemia are seen when levels drop below 18 ppm in cattle . 1 There may be a considerable lag between development of hypomagnesemia and appearance of clinical signs . Signs of tetany often coincide with development of acute hypocalcemia with preexisting hypomagnesemia . 1
Acute signs are observed with a rapid decline in serum magnesium , such as when a ruminant is put on lush pasture (“ grass staggers ”). Chronic hypomagnesemia usually develops over months ( typically in the winter ) in response to a marginal diet . 5 Clinical signs include reduced growth rate or body condition , nervous signs ( twitching ears , kicking at abdomen , hyperexcitability , chomping jaws , frothy salivation ), tetany and seizures . Signs can be precipitated by stress , and may progress to death . Although the whole herd may be involved , usually only a few animals show clinical signs during any given period .
Role of feed management – Rumen acidosis can be a cause of mineral imbalances . Improper feed management can lead to subacute and chronic rumen acidosis . Decreased rumen pH is associated with intake of fermentable carbohydrates , decreased effective fiber intake , stress ( heat , illness ), and overall decreased feed intake . 2 Signs associated with rumen acidosis are : laminitis , poor body condition , variable daily feed intake , abnormal rumen motility , and changes in fecal consistency ( diarrhea , or foamy undigested feed ). Factors that may prevent chronic rumen acidosis include : avoiding limited access time to feed concentrates or competition for feeders ; providing adequate roughage ( long stem hay ); addition of buffers and fiber to the diet ; providing environmental changes to decrease heat stress ; providing a balanced diet ; and minimizing stress .
Data collection
Serum samples for mineral analyses were submitted to Michigan State Animal Health Diagnostic Laboratory ( Lansing , MI 48909 ). A database encompassing four years of data was compiled . Most ungulates were fed a commercial pelleted diet ( Mazuri ADF 16 or 25 , St . Louis , MO ), small amounts of produce , alfalfa and / or Bermuda grass hay , and fresh cut browse . Animals were fed in barns or holding areas . In addition , animals had access during the day to a habitat containing multiple species of grasses , shrubs , and trees . Although data regarding consumption of diet fed is available , amount of habitat vegetation consumed is unknown .
Results
Initially , results were compiled to determine this collection ’ s reference ranges for each species . Periodically a low magnesium was noticed in an individual sample obtained during a routine procedure . The first indication of possible clinical signs associated with hypomagnesemia occurred in an adult female kudu ( Tragelaphus strepsiceros ) in January 1999 . Initially this animal presented for weight loss , rough hair coat , and retained placenta following birth of a weak calf . She later had an acute onset of muscle fasciculations , hunched posture with stiff gait , and lethargy . Her values at that time showed hypocalcemia and hypomagnesemia ( Ca = 4.8 mg / dl , P = 8.2 mg / dl , Mg = 12 ppm ).
A second female kudu showed tetanic muscle contractions during the first trimester of pregnancy . This animal had serum Ca = 6.0 mg / dl , P = 10.0 mg / dl , and Mg = 8.06 ppm . A review of records showed that six months previously this animal had a dystocia and bloodwork at that time revealed serum Ca = 7.1 mg / dl , P = 8.7 mg / dl , and Mg = 9.34 ppm . Animal care staff noticed bilaterally symmetric facial and cervical alopecia on three adult male kudu . These animals
2018 MAY 15