Question:  I have a 4 year old PRE mare that I bought as a 2 year old. I have recently noticed that her hind pasterns seem to be 'softer' so that her fetlocks sink lower in movement than I have noticed in the past. This is something I have experienced with another PRE horse that I 3 years he seemed fine, but as he got older the fetlocks seemed to sink. I also notice periodic collapsing of the mare's stifles, and have had other horses diagnosed as neurologic so find this worrisome. Could this possibly be due to a nutritional deficiency? Or perhaps excess potassium or nitrates in the pasture or hay interfering with calcium, phosphorus, magnesium and salt balance? I have worked with a local nutritionist and believe that I am feeding a balanced diet of mostly grass hay (15 lbs) with a flake of alfalfa (5 lbs) supplemented by a few cups alfalfa pellets mixed with California Trace, ground flax seed, salt and a natural liquid form of vitamin E. I worry about the possibility of DSLD as well as some sort of neurological condition. The previous horse was ultrasounded, but the study was inconclusive for DSLD and I was told it may be to soon to tell. I would like to be proactive. I read about the possible benefits of arginine and jiaogulan. Would it be safe and reasonable to try supplementing with these? Which product and amounts do you recommend? Is there another supplement I should be feeding such as amino acids or magnesium oxide? This horse is a good weight, has very good hoof form and is not IR in my opinion. Thank you so much for your help.

Dr. Kellon: It's not unusual for this breed to show quite a bit of "give" in their fetlocks, which may contribute to their fluid and elastic gaits. This will become more obvious as the horse matures and gains weight and it is not necessarily indicating a problem. If there is any question, fetlock flexion tests will be markedly positive with DSLD and ultrasounds are the best diagnostic tool. There is a diagnostic protocol that employs actual ultrasound measurements detailed here:   
There are many nutrients involved in tendon and ligament health and production.  Your diet is a good start but I would advise hay analysis to make sure your mineral supplement is adequate. You can also use Uckele Tri-Amino to assure adequate essential amino acids. If there is any indication of swelling, heat or pain I would use LaminOx.