Some symptoms of 5 Horses prior to being euthanized: diarrhea, colic, comminuted fractures of 5th and 6th lumbar vertebrae, rupture of five torn ligaments and tendons, rupture of fetlock joint capsule, complete fracture of the humerus, cartilage erosion... This is horseracing.

Through a FOIA request to the California Horse Racing Board, I have
obtained the following details on some of that state’s kills last
year (more can be found here:
Death Reports, California).
My Patate, Jun 28, Santa Anita S
“Gelding had diarrhea Jun 27, displayed signs of colic overnight,
died spontaneously during early morning Jun 28.” My Patate was ten
years old.
Flying Cowgirl 321, Aug 12, Los Alamitos R (euth Aug 14)
“Ran Aug 12, came back ‘tied up’ per trainer. Aug 14, found down in
stall unable to rise: complete, displaced, comminuted fractures of
the 5th and 6th lumbar vertebrae with subsequent compression of the
adjacent spinal cord.” Flying, just two years old, had broken her
back – and wasn’t euthanized for two days.
Thundering Eagle, Sep 10, Los Alamitos R
“[Multiple] open, displaced, comminuted fractures; [multiple] torn
ligaments and tendons; complete rupture of fetlock joint capsule;
severe hemorrhage; severe laceration.” Thundering was but two years
old.
Hangin At Haven, Oct 4, Golden Gate T
“Horse fell while galloping: complete fracture of the humerus.”
Also: “cartilage erosion [both front limbs]; multiple stomach
ulcers.” Hangin was just two years old.
Geaux Rocket Ride, Oct 28, Santa Anita T (euth Nov 1)
“Open [through the skin], displaced, comminuted fracture with
rupture of several [I counted at least five] tendons and ligaments.”
With this obvious catastrophic injury, they still tried to operate.
Of course: Geaux was an intact (could still be used for stud), $1M,
Grade 1 horse. The surgery involved, among other things, a
compression plate, 15 screws, and a tension-band wire. After that
surgery on the 29th, “horse could not stand and was treated for
bilateral muscle myopathy and bilateral nerve paralysis.” Still
unable to stand (“even with sling support”) on the 1st, Geaux,
three, was finally euthanized. Evil.