I had a mule a few years ago
that when I got her, would have a meltdown at the mere sight of a
syringe. I started working with her everyday. I used carrot baby food
in the syringe. At first I would show her the syringe and as she was
getting ready to explode, I would have a treat ready. I would not get
the syringe any closer to her and she would eventually take the treat.
After a few days, she finally started associating the treat with the
sight of the syringe. So, after about a week, I could get the syringe
close to her. Finally, I just brushed the syringe across her mouth with
the baby food carrots all over it. She got nervous the first few times
but liked the baby food carrots. By the end of the second weeks, All I
had to do was hold the syringe out and she would literlly grab it and
if I didn't hold on tight, she would nearly eat the syringe!!!!
I did this so I could worm her without a fight. And the wormings were
fine once I worked her though this. I would just make sure to
occasionally offer her baby food carrots between wormings so she would
keep expecting that MOST of the time the syringe was something good.