Short answer. Only in narrow circumstances. Article 1578 of the Civil Code makes the seller liable if the animal died within three days after the purchase and the disease that caused the death already existed when the contract was made. Outside that window you fall back on the ordinary hidden-defect rules.
What the law says
If the animal should die within three days after its purchase, the vendor shall be liable if the disease which cause the death existed at the time of the contract.
Civil Code, Article 1578 — Death of the Animal Within Three Days. Read the full provision →
Two conditions, and both must hold
The provision is short and exacting: If the animal should die within three days after its purchase, the vendor shall be liable if the disease which cause the death existed at the time of the contract. That is one rule with two separate requirements. The death must fall inside the three-day period, and the cause of death must be a disease that the animal was already carrying when you bought it. Miss either and this particular article gives you nothing. It is a rule about latent sickness in livestock, framed to stop a seller from passing off an already-diseased animal and then blaming the buyer's handling once the animal is off his premises.
The clock runs from the purchase, not the delivery
This catches many buyers out. The article counts three days after its purchase — the perfection of the sale — and not from the day the animal reached your farm or yard. Where the sale was agreed on one day and the animal arrived several days later, the three-day period may already have run out by the time you took possession. If purchase and delivery happened together, the two dates coincide and the point does not arise. Either way, fix the date of the contract from a document — a receipt, a delivery note, a message thread, a bank transfer — before you argue about anything else.
Proving the disease was there before the sale
The liability turns on the animal's condition at the time of the contract, so the evidence has to reach backwards. A post-mortem examination by a veterinarian is the single most useful step, and it has to be done quickly, because a carcass left for days may tell nobody anything. A veterinarian can often say whether the incubation or progression of the illness is consistent with infection before the sale. Vaccination and treatment records from the seller's herd, the health of the other animals he sold, and any transport or quarantine papers all help. Photographs and dated messages describing the animal's condition on arrival are worth keeping too.
What the article does not cover
It does not make a seller an insurer of the animal's survival. A death from an accident, from mishandling, from the stress of transport arranged by you, or from feeding or housing after delivery falls outside it entirely. It also does not cover an animal that merely turns out to be weak, unproductive or not what you expected — a live animal with a hidden defect is dealt with under the Civil Code's general rules on hidden defects in a sale, which give the buyer a choice between undoing the sale and keeping the animal with a reduction of the price. Those rules carry short deadlines of their own, so raise the complaint in writing at once rather than waiting.