Iron levels drop 5 hours after the onset of inflammation and can further drop by as much as 75% in comparison to normal levels, after just 24 hours. The lower the level of iron the greater the chances are of organ failure including failure of the hoof, iron levels appear to be an accurate prediction of the severity of the symptoms. Usually fibrinogen is the most commonly measured level to indicate inflammation but fibrinogen can take 24 hours to rise and may not peak for 2-3 days. Free iron levels appear to drop even ahead of the first neutrophil response of the immune system.
Systemic Inflammation causes multiple organ failure and is also a cause of laminitis, horses with laminitis caused by SIRS often suffer the most devastating failures of the structures of the foot.
The lowered iron levels are thought to be due to less being absorbed from the gut and also less being released by the cells, this occurs rapidly after the onset of inflammation as the body seeks to defend itself against the replication of invading pathogens. The ability of pathogens to obtain iron from their host is central to whether they live or die. To combat invading bacteria, horses go into an iron-withholding mode and use a special protein to generate reactive oxygen species in an attempt to kill the pathogens. Some invading bacteria respond by producing specific iron extractors and transporters—that remove the iron from the host sources, whilst other bacteria rely on direct contact with host iron proteins.
As anaemia in horses is said to be rare and low iron levels are indicative of an infection or inflammation, does this mean that supplementation/injection of iron is dangerous, because iron actually helps to proliferate the endotoxins?
Of the 97 horses with systemic inflammation that were included in a trial, 28 had acute 19 had subacute and 50 had chronic inflammatory conditions. Horses with subacute and chronic inflammation also had significantly raised fibrinogen levels.
Visual signs of (pre SIRS) and pro-inflammatory states are
Prominent growth rings on the hoof wall
Dished hoof wall with flared out long toes (and often low compacted heals)
Low grade seedy toe, sub solar haematomas, and or an abscess
Crumbly white line.
Flaky soles and hoof edges broken away
Sore or pottery front feet which is more evident on hard ground
Shortened gait that doesn't improve with exercise and worsens with fast and hard work.
There are some factors which might affect the accuracy of using iron levels to detect inflammation –these include liver disease and internal bleeding events such as EEIPH"