Now, let us check the form of てみる again.
And from your original sentence,
and up to this point except for てみると is O.K to me.
Speaking of horsemeat, even though I think that it is kyushu and especially Kumamoto,
And you are wondering if the verb "try out" is needed.
By the way, since who checked which prefectures produced horsemeat many, it is not "you" but "I"
Speaking about the conclusion, the answer ( translation ) would be
After I checked ( may be here it is better for you to write what you checked up ( ex, dictionaries, books etc ) up ( again ( I think adding the word again would be nicer IMO ))
The reason is, from the source at the first line,
the てみる in question is
(1) Denote the action to try as a test to accomplish a purpose, I tried the new beer if it tastes well.
Now here is the problem. In your case you do not need to insert "try out", here in turn, English sounds strange to me.
So I personally recommend for you to use "after I checked up" instead.
The another reason would probably your sentence in question would rather sound near the definition (4)
Denote the action to find out something. I fount this place is good to live after I have lived for a while.
The nuance in question in Japanese sounds similar to the definition of (4).
The person who is interested in the production of horsemeat does not have a strong desire to "try to check" but only occasionally found out the amount of the production of the horsemeat in Aomori prefecture ranked in 3rd.
I hope you understand.