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PG . 43 heavily on the calcium reserves stored in her own skeleton and mares on borderline or low calcium intakes have lower blood calcium and reduced bone density and strength . Mares gradually lose bone density during the first 3 months of lactation , but by 6 months after foaling , bone strength is restored if dietary calcium intake is correct . Mares on below recommended calcium intakes had still not restored their bone density at 10 months after foaling . And , foals of mares on sub-optimal calcium intakes had thinner , weaker cannon bones even at 10 months of age .
Magnesium ( Mg ) deficiency occurs when dietary levels are too low or when demand for magnesium increases - such as during long distance transportation , pregnancy and lactation . Low blood magnesium is more likely in highproducing mares , especially if transported long distances without feed . It is recommended that pregnant and lactating mares receive 10-15g of magnesium each day . Typical diets often do not meet magnesium requirements and deficiency has been linked to developmental bone diseases in growing horses . Supplementing foals with magnesium from birth to 12 months of age resulted in a 50 % reduction in OC of the hock and fetlock at 5 months of age and a 14 % reduction in stifle OC at 12 months of age . There are other veterinary clinical conditions in pregnant and lactating mares that are associated with calcium and magnesium . Blood calcium and magnesium levels have been found to be low in mares who retain the placenta and in some colic cases . Broodmares are at increased risk of colic – especially from 7 days before to 90 days after foaling . Low levels of blood calcium and magnesium can alter gut motility and a recent study found that mares with post-foaling colic showed signs of acute , sudden dietary energy deficiency and lower blood calcium for 2-4 weeks before and after foaling .
Low levels of blood calcium and magnesium can occur simultaneously in transported horses and in pregnant and lactating mares . Compared to other species , mares aren ’ t very prone to ‘ lactation tetany ’ ( also called ‘ milk fever ’ and pre-eclampsia ), which occurs when the calcium demand
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2024 AQHA ~ NOVEMBER / DECEMBER ISSUE