That's easy:
0.6mg/kg X 410kg/1 X 1tab/15 mg = 16.4 tablets
[this type of mathematical procedure is called unit analysis; using the units to set up the problem correctly.]
Given that 0.4 of a tablet is only about 2% of that overall dose, you could go with 16 tablets and not worry about cutting/breaking one.
The real question, though, is if the dosage is the same for horses as for people. Different animals metabolize thing differently, and might have a different dosage requirements. For example: an 'average' sized (~4-5 lbs) chicken can have an 81 mg. aspirin tablet. If I took 81 mg. tablets (1 per 5 lbs), I would be taking over 3,000 mg of aspirin. That is way too much for a human dose. (i.e. for a 150 lb. person, that would be 30- 81 mg tabs, or 2,430 mgs! The supposed human dose is 300 - 650 mg. Clearly there is a real disconnect there between human dosing and chicken dosing.
I have no idea regarding equestrian dosing - just wanted you to make sure the dosing is the same BEFORE giving her some!
Okay, I hopped on here because I saw @Ponypoor tagged me, but I have to get back to work on my course now.
I got to read a few pages, but gosh am I behind. Hopefully the 'issues' with the new LMS will let up and I can catch up this weekend.
Hope everyone is well. My momma hen is doing great with her 5 babies (now, if I could only get her to tone down her scratching and get her to stop flinging her feed dish while doing so,
all would be well with the chicken world here!
(P.S. I have a BR girl who thinks she wants to hatch...she has picked a good nest box, but it is empty! She has sat on nothing for 3 days now. I'll give her a few eggs tomorrow if I get a chance - else it will be this weekend. I do hate having her broody for almost a full week before getting eggs, though. It is hard enough on them as it is, without making the 'to hatch' time even longer.)