The ruling on fattening sheep to make them swell before selling them

Question:
A person who has sheep and is preparing them for sale fattens them and feeds them before offering them for sale. Is there anything prohibited in that?

Answer:
And what is the obstacle? He fattens them until they become fat and benefit him. As for milk, he must not deceive people with milk. But as for fattening them and leaving them for two or three weeks so that they increase in weight, there is nothing wrong with that.
Q: Some of them give them water and salt so that they swell?
The Shaykh: No, the thing that involves deception is not permissible. But fattening is normal; there is nothing wrong with it. He fattens them; it is required of him to fatten them so that they benefit him... But deception is not permissible. The thing that makes them swell is not permissible, or... likewise, he collects milk in them and says it is from the morning, when it is not from the morning; it is yesterday's milk, this morning's milk, and the day before yesterday's milk. This is not permissible; it is deception.