Cum hiems venit, vaccis fenum damus, et palea quoque in stabulo manet.

Here cum means when.

It is introducing a time clause: Cum hiems venit = When winter comes.

This is not the preposition cum meaning with. You can tell because it is followed by a whole clause with a verb (venit), not by a noun in the ablative.

Because this is a straightforward temporal clause: when winter comes.

Latin often uses cum + indicative when it simply states when something happens as a fact. If cum were being used in a more causal or circumstantial way, especially in more advanced prose, you might see the subjunctive instead.

So here:

• cum hiems venit = when winter comes

It is simple and factual.

The present tense here expresses a general or habitual idea:

• When winter comes, we give hay to the cows...

In English, we also often use the present for this kind of thing: When winter comes, we... It does not have to mean this exact moment; it can mean whenever winter comes or as winter arrives each year.

Hiems is nominative singular, and it is the subject of venit.

So:

• hiems = winter
• venit = comes

Together: winter comes.

Because vaccis is the indirect object: the cows are the ones to whom the hay is given.

With do, dare (to give), Latin commonly uses:

• accusative for the thing given
• dative for the recipient

So in:

• vaccis fenum damus

we have:

• fenum = the thing given
• vaccis = to the cows
• damus = we give

Because Latin often expresses to by using the dative case, not by adding a separate word.

So English says:

• we give hay to the cows

Latin says:

• vaccis fenum damus

where vaccis already means to the cows because of its case ending.

Fenum is the direct object of damus, so it is accusative singular.

It is the thing being given:

• we give hay

A useful detail: fenum is a neuter noun, and in the singular its nominative and accusative forms look the same. So the form is fenum either way, but here its function is accusative because it is the object of damus.

Because the ending of the verb already tells you the subject.

• damus = we give

The -mus ending shows we, so Latin does not need nos unless it wants extra emphasis:

• damus = we give
• nos damus = we give / we are the ones who give

In ordinary sentences, Latin often leaves the subject pronoun out.

They are not the same thing.

• fenum = hay
• palea = straw

So the sentence is distinguishing two different materials:

• hay is given to the cows
• straw remains in the stable

That is a practical farm vocabulary distinction, and Latin keeps it clear.

Because palea is in the nominative singular, and manet is singular too.

So:

• palea manet = the straw remains

The structure of the second clause is:

• et = and
• palea = straw
• quoque = also / too
• in stabulo = in the stable
• manet = remains

Because palea is being treated as a singular mass noun here: straw.

English does the same thing. We usually say:

• the straw remains

not

• the straw remain

So Latin uses the singular verb:

• palea manet

Because in takes different cases depending on meaning:

• in + ablative = in / on a place, showing location
• in + accusative = into / onto a place, showing motion toward

Here the meaning is in the stable, meaning location, so Latin uses the ablative:

• in stabulo = in the stable

If it meant into the stable, you would expect in stabulum.

Quoque means also or too.

So:

• palea quoque = the straw too / straw also

The word et is still needed because it joins this clause to the previous one:

• ..., et palea quoque in stabulo manet
• ..., and the straw also remains in the stable

So the two words do different jobs:

• et = connects clauses: and
• quoque = adds emphasis: also / too

Because quoque is often placed after the word it emphasizes.

So:

• palea quoque = straw too

This is a very common Latin pattern. The placement helps show what is being marked as also.

Yes, the word order is normal Latin.

Latin word order is more flexible than English because the case endings show the grammatical roles. English depends much more on position.

A very literal order would be:

• When winter comes, to-the-cows hay we-give, and straw also in the stable remains.

That sounds strange in English, but it is perfectly natural in Latin.

A few things to notice:

• the verb often comes late in the clause
• important words can be moved for emphasis
• cases tell you who is doing what

Because Latin has no articles like English the and a/an.

So:

• hiems can mean winter or the winter, depending on context
• vaccis can mean to cows or to the cows
• in stabulo can mean in a stable or in the stable

English has to choose an article; Latin usually leaves that for the reader to understand from context.