maintaining horse weight

[guest@endurance.net]

leah mellott royleah@desupernet.net
     I have a very young 16 year old morgan mare.  She is a "hotter" mare
with a high natural heart rate and metabolism.
I have been conditioning her for two years for longer rides.  Her fitness
and endurance is fine but I am having a
problem keeping weight on.   I have had a vet out to cover all the bases;
parasites are negative, blood work came out
fine, and thyroid is also normal.  I have her on grass and hay, she is
getting almost 9lbs of feed a day  (A mix of 10%
alfalfa pellets, and pennfield enduraevent).  She keeps getting thin in
the flank area and sometimes some along the
topline and ribs. Any help is appreciated.