Atlara temiz kuru ot sermek onların rahat uyumasını sağlar.

Atlara is at + plural -lar + dative -a, so it means to the horses / for the horses.

With sermek here, the thing being spread is ot (hay / grass), and the horses are the ones it is spread for. So:

• Atlara ... ot sermek = to spread hay for the horses
• Ot is the thing being laid out
• Atlara shows the target/beneficiary

If you said atları, that would be the accusative form the horses, which would make it sound like the horses themselves are the direct object.

Sermek means to spread, lay out, strew.

In this sentence, it refers to laying out bedding material or hay for the horses. So temiz kuru ot sermek is something like:

• to spread clean, dry hay
• to lay down clean, dry hay

It is not about feeding them here; it is about preparing a comfortable place.

No word is missing. In Turkish, multiple adjectives can simply be placed one after another before the noun.

So:

• temiz kuru ot = clean dry hay

This is very normal in Turkish. You do not need ve (and) between adjectives in this kind of description.

Yes. The whole phrase Atlara temiz kuru ot sermek functions as the subject of the sentence.

Literally, it is:

• Spreading clean dry hay for the horses ... ensures ...

In Turkish, an infinitive in -mek / -mak can act like an English -ing form or infinitive noun phrase:

• yüzmek = swimming / to swim
• okumak = reading / to read
• sermek = spreading / to spread

So here, sermek turns the action into something that can be the subject.

Onların means their or of them.

It refers back to the horses. Turkish often uses a pronoun instead of repeating the noun, just like English can say:

• Spreading hay for the horses ensures their comfortable sleep

Instead of repeating the horses’, Turkish uses onların.

You could also say atların rahat uyumasını sağlar, but onların is perfectly natural when the reference is already clear.

Because Turkish often uses a nominalized verb instead of a full that-clause.

English says:

• ensures that they sleep comfortably

Turkish often turns sleep into a noun-like form:

• onların rahat uyuması = their sleeping comfortably

Then because it is the object of sağlar, it becomes:

• onların rahat uyumasını

So Turkish is using a noun-like subordinate structure where English often uses that + subject + verb.

Yes:

• uyu- = verb stem from uyumak (to sleep)
• -ma = verbal noun / nominalizer
• -sı = 3rd person possessive
• -nı = accusative case

So:

• uyuması = his/her/its/their sleeping
• uyumasını = his/her/its/their sleeping as a definite direct object

Because it follows onların, the pattern is:

• onların uyuması = their sleeping
• onların uyumasını = their sleeping as the object of sağlar

This is a very common Turkish structure.

In subordinate clauses of this kind, Turkish often uses:

• a genitive possessor: onların = their
• a possessed nominalized verb: uyuması = their sleeping

Then, if that whole phrase is the object of another verb, it also takes the accusative:

• onların rahat uyumasını sağlar
• literally: it ensures their sleeping comfortably

So the possessive ending is part of the subordinate clause structure, and the accusative shows that the whole thing is the object of sağlar.

Rahat can function very naturally in Turkish as an adverb-like word meaning comfortably / in comfort.

So:

• rahat uyumak = to sleep comfortably

You may also see rahatça in some contexts, but rahat uyumak is extremely common and natural.

Sağlar comes from sağlamak, which means:

• to provide
• to ensure
• to make possible
• to enable

In this sentence, ensures is the best fit.

So:

• ... sağlar = ... ensures / makes it possible

Sağlar is the aorist / simple present form.

In Turkish, the aorist is often used for:

• general truths
• habitual actions
• statements of what something typically does

Here it means something like:

• Spreading clean dry hay for the horses ensures ...
• ... tends to ensure ...
• ... is something that ensures ...

This is a very natural choice for general statements.

Yes, Turkish word order is flexible, although some versions sound more neutral than others.

This sentence is quite natural as it is:

• Atlara temiz kuru ot sermek onların rahat uyumasını sağlar.

It could also be rearranged for emphasis, for example:

• Onların rahat uyumasını atlara temiz kuru ot sermek sağlar.

But that sounds more marked or emphatic. The original version is a straightforward neutral sentence.

Good question. Ot can mean:

• grass
• herb
• sometimes hay / fodder, depending on context

In this sentence, because the hay is being spread out so the horses can sleep comfortably, ot is best understood as bedding material or dry fodder-like grass. So hay is a natural translation here, even though ot is a broader word than English hay.

A fairly literal translation would be:

• To spread clean dry hay for the horses ensures their sleeping comfortably.

That is understandable, but not natural English.

A more natural English translation is:

• Laying clean, dry hay out for the horses helps them sleep comfortably.
• Spreading clean, dry hay for the horses ensures that they sleep comfortably.

So the Turkish structure is a little more noun-based than natural English.

Because Turkish usually does not need a separate word like English that in this kind of sentence.

Instead of:

• ensures that they sleep comfortably

Turkish builds:

• their sleeping comfortably

So the that-clause idea is expressed through the nominalized form uyumasını, not through a separate word.