Translation:The specimen has been fully consumed.
The reason why not natlhchu'pu' chovnatlh is that in your sentence the specimen consumed something. But in the original sentence, the specimen was consumed by something.
To express that, you have two choices.
chovnatlh natlhchu'pu' vay'
or else use the suffix for an unknown doer, -lu', to get the passive voice sentence in English of the specimen was consumed by some unmentioned subject.
chovnatlh natlhlu'chu'pu'. Here the subject is never mentioned. You can only do that using lu'.
One thing that might help with these kinds of sentences until they become second nature is to notice that there is something in the object position but nothing in the subject position. That should alert you that it is a -lu' suffix sentence. But that will not be the case when the subject is only indicated by a prefix or in complicated sentences perhaps with bogh or something. I can't think of an example but I can imagine there could be cases. Maybe the best thing is to keep an eye out for the -lu' suffix (not lu- prefix!) and remind yourself that the subject of the English sentence is actually the object of the Klingon sentence and that you need to fix that discrepancy by translating it into the English passive voice.
Basically if you see the English passive voice, you need -lu'. If you see -lu', you need the English passive voice. This can get a bit confusing because often English copulas look like the passive voice.
"She is happy" is a copula type sentence and she is the subject in both the English and Klingon sentence. Quch ghaH or Quch.
"She is found" is a passive sentence with she as the subject but not the doer in the English sentence but the object in the Klingon sentence. ghaH Samlu' or Samlu'.
With English sentences that use 'to be', pay attention to who is doing the action of the verb. Is it the subject of the sentence or some unnamed person/thing. Then you know what Klingon construction to use.
I paused at this sentence when I first encountered it as well. They key point is that natlh is defined strictly as a transitive verb in Klingon, such that "to be consumed" implies that something else did the consuming. This is a bit different than in English, where "consume" can be used either transitively or intransitively (to mean "waste or burn away"). See: https://www.merriam-webster.com/dictionary/consume
This is true. When a verb can take an object, it doesn't have to. Use the appropriate no-object prefix to indicate a sort of "general object."
jISop I eat (things in general).
jISuv I fight (things in general).
As for natlh, this verb means use up, not be used up. Those are two different concepts, and the distinction in important in Klingon.
chovnatlh natlh tej
The scientist uses up the specimen.
The specimen is being used up.
chovnatlh natlhpu' tej
The scientist used up the specimen (It's all gone now.)
The specimen is used up (it's all gone now).
I changed something in what I wrote above so reread it please. I want it to be as clear and accurate as possible to not misdirect people.
I had said that one thing to look for is the clue of there not being a subject, but that is not true when the prefix is the only indicator of the subject in a sentence. So really, looking for suffix -lu' is the best thing to do.
Awesome. Oh, yes, I see that you have a lot of Spanish XP. It has the subject sort of included in the verb. I just started learning it. I am not very far. Greek does the same thing so you don't have to use pronouns in Greek either. It is sort of cool. Concise. Efficient. Eliminates redundancy. I like it.