Bava Metzia 78: Liability for Rented Animals when Something Goes Wrong

At the end of our the Gemara, we learn that one may hire another person to do the work of a labourer who has reneged.  That is, a donkey driver or a potter.  Rav Nachman teaches that these new workers can be paid up to the agreed upon wage with the initial labourers.  This makes me think of what might be done when workers strike due to poor working conditions.  I assume that the work-around in this scenario is the assumption that the labourers were breaking an agreed-upon contract when they decided to strike.  Because if an employer can hire new workers to do his work when his initially hired workers have legitimate concerns, this would be very concerning. And not in line with other rabbinical decisions regarding labourers and contracts.

A new Mishna teaches us about liability for an animal's injury or death while working.  If a person is hired to take a donkey up a mountain or down a valley and he takes the animal in the opposite direction, he is liable if the animal dies even if the distance is equal. If the animal was wrongly taken into the valley and it slipped on the terrain, he is exempt, but if the animal died of heatstroke he is liable, for the temperature is hotter in the valley.  If the animal was wrongly taken up a mountain, if the animal slipped he is liable and if the animal died due to the ascent, he is also liable.  If that animal died of heatstroke, he is exempt.  If a rented donkey becomes ill or is seized for public service, the owner can say, "That which is yours is before you".  However, if the donkey died or broke a leg, the owner must give the renter a replacement donkey.

The Gemara offers other examples to discuss concepts of leniency in the use of designated items, like wool being dyed different colours and the use of Purim funds.  The rabbis discuss the importance of the stated intention for the use of any particular item when it is borrowed, rented or sold.  Finally, we learn about the different implications of saying "That which is yours is before you".  It is exceedingly clear that the rabbis are intent upon creating and applying halachot in a balanced and fair-minded manner.