Eu alimento o filhote com ração.

Yes. In Brazilian Portuguese, eu is often optional because the verb form alimento already shows that the subject is I.

So both of these are natural:

• Eu alimento o filhote com ração.
• Alimento o filhote com ração.

Including eu can add emphasis, contrast, or clarity.

For example:

• Eu alimento o filhote, e ela dá água.
  = I feed the baby animal, and she gives water.

Yes. Alimento here is the first-person singular present tense of the verb alimentar.

• alimentar = to feed / to nourish
• eu alimento = I feed

Be careful: alimento can also be a noun meaning food in other contexts.

Examples:

• Eu alimento o filhote. = alimento is a verb.
• Este alimento é saudável. = alimento is a noun meaning food.

Portuguese often uses definite articles more than English does. So o filhote literally means the baby animal / the young one, but in many contexts English would simply say the puppy, the cub, or even just it, depending on what is already known.

Using o usually means the speaker has a specific animal in mind.

Compare:

• Eu alimento o filhote. = I feed the baby animal.
• Eu alimento um filhote. = I feed a baby animal.

No. Filhote is a general word for the young of an animal. Depending on context, it can mean:

• puppy
• cub
• chick
• baby animal
• young one

So it is broader than English puppy, which is specifically a young dog.

If the context is a dog, filhote can absolutely refer to a puppy. But by itself, the word is not limited to dogs.

Ração usually means animal feed, pet food, or feed. In Brazilian Portuguese, it is very commonly used for dry pet food or prepared animal food.

So com ração means with pet food / using feed.

Examples:

• ração para cachorro = dog food
• ração para gato = cat food
• ração para galinhas = chicken feed

It sounds more specific than a general word like comida.

• comida = food in general
• ração = feed/pet food/animal food

Both are possible, but they mean slightly different things.

• com ração = with pet food / using feed in general
• com a ração = with the pet food / with that specific feed

In your sentence, com ração sounds natural because it refers to the type of food, not a specific portion or bag.

Compare:

• Eu alimento o filhote com ração. = I feed the baby animal with pet food.
• Eu alimento o filhote com a ração que o veterinário recomendou. = I feed the baby animal with the pet food that the vet recommended.

The most natural order is:

• Eu alimento o filhote com ração.

That follows a very common pattern: subject + verb + object + complement

You can move things around in Portuguese, but some orders sound more formal, marked, or less natural in everyday speech.

• Eu alimento com ração o filhote is understandable, but it sounds less natural in normal conversation.
• Com ração, eu alimento o filhote is possible if you want to emphasize ração.

So for a learner, the original word order is the best default.

It is the present indicative.

In Portuguese, the simple present can cover several ideas that English splits up:

• I feed
• I do feed
• sometimes even I am feeding, depending on context

But if you specifically want to emphasize an action happening right now, Brazilian Portuguese often uses:

• Estou alimentando o filhote com ração.
  = I am feeding the baby animal with pet food.

So:

• Eu alimento o filhote com ração. often sounds habitual or general.
• Estou alimentando o filhote com ração. sounds clearly in progress right now.

The article and sometimes the noun change according to gender and number.

Singular masculine:

• o filhote

Singular feminine:

• a filhote
  This can be used when the animal is female.

Plural masculine or mixed:

• os filhotes

Plural feminine:

• as filhotes

Examples:

• Eu alimento a filhote com ração. = I feed the female baby animal with pet food.
• Eu alimento os filhotes com ração. = I feed the baby animals with pet food.

Alimentar is correct and natural, but in everyday speech Brazilians may also use more informal expressions, especially with pets.

Common alternatives:

• dar ração para o filhote = to give pet food to the baby animal
• dar comida para o filhote = to give food to the baby animal

Examples:

• Eu alimento o filhote com ração.
  Correct, clear, slightly more formal or neutral.
• Eu dou ração para o filhote.
  Very common in everyday speech.

So your sentence is perfectly good, but it is useful to know that spoken Brazilian Portuguese often prefers dar in this kind of context.

A rough pronunciation is:

• ração ≈ ha-SOWN, with a nasal ending

A few important points:

• The r at the start of ração is pronounced like an English h in most Brazilian accents.
• ç sounds like s.
• ão is a nasal sound that does not exist exactly in English.

So:

• ração sounds roughly like ha-SOWN, but with the final sound nasalized rather than fully pronounced like English own.

Also, the stress is on the last syllable:

• ra-ÇÃO

Yes, that is exactly how com works here: it introduces the means or substance used to feed the animal.

In English, with can also do this:

• I feed the puppy with kibble.

Portuguese uses com very naturally in this structure.

You could also rephrase the sentence:

• Eu dou ração ao filhote.
• Eu alimento o filhote usando ração.

But com ração is simple and idiomatic.