Greg,

I read the quote to mean that slaves were considered expensive livestock - remember that to the slavers/slave holders the slaves WEREN'T considered human (a standard slave shippers' term, I believe, was "black cattle") and that the slave holder would try to look after what was considered an investment, not necessarily from any feeling for the slave, but simply that a sick or ill nurished slave was less productive and/or had a lower resale value.

Ducking back behind the parapet

Regards

Walrus