Short answer. Likely yes, if they were bought as a team. Article 1572 presumes you would not have bought the sound animals without the defective one when a team, yoke pair, or set is purchased, even if each animal had a separate price, letting you return the whole group rather than just the defective one.
What the law says
the redhibitory defect of one shall only give rise to its redhibition, and not that of the others; unless it should appear that the vendee would not have purchased the sound animal or animals without the defective one
Civil Code, Article 1572 — Redhibitory Defect When Several Animals Are Sold. Read the full provision →
What the law says
The latter case shall be presumed when a team, yoke pair, or set is bought, even if a separate price has been fixed for each one of the animals composing the same.
Civil Code, Article 1572 — Redhibitory Defect When Several Animals Are Sold. Read the full provision →
The general rule: only the defective animal is returned
Article 1572 starts from a default that limits redhibition to the animal actually affected. It provides that when two or more animals are sold together, the redhibitory defect of one shall only give rise to its redhibition, and not that of the others, whether the animals were bought for a lump sum or at separate prices. Ordinarily, a hidden defect in one animal does not let you undo the purchase of the healthy animals bought alongside it; each animal's soundness is treated as its own separate matter.
The exception when the healthy animals were bought for the defective one's sake
The article immediately qualifies that default rule: the outcome changes unless it should appear that the vendee would not have purchased the sound animal or animals without the defective one. If the real reason you bought the healthy animals was that they came together with, or worked together with, the one that turned out defective, the defect is treated as affecting the whole purchase, and you are not limited to returning only the flawed animal.
Buying a team or pair triggers a presumption in your favor
Article 1572 makes this exception much easier to invoke in exactly your situation: The latter case shall be presumed when a team, yoke pair, or set is bought, even if a separate price has been fixed for each one of the animals composing the same. Work animals bought together as a team or pair are presumed to have been bought precisely because they function together, so you do not have to separately prove you would not have bought the sound one alone; the law assumes it once the animals were purchased as a team.
What this means for your defective work animal
Because your animals were bought as a team, the presumption under Article 1572 works in your favor: you are entitled to return the whole team, not merely the one with the hidden defect, unless something in the facts overcomes that presumption, such as clear evidence the animals were really independent purchases that happened to occur at the same time rather than a genuine working pair or set.