The only time I ever had a problem with an injection was when the vet
gave it in the pectoral. After a few days, the sight swelled & the horse
was sore for several days. When the hard swelling went down the area was “baggy”
for a few weeks or more. . I did some research, and read that often this
swelling leaves a permanent baggy chest area and so is not used often for
injections.
Kathy
The other choice is the pectoral muscles--easy for the one giving the
shot, and ideal downward drainage in the event of abcessation.