Life for the animals at Manor Farm resembles a third world agricultural exploitation which would not be eligible to receive the "Fair Trade" seal of approval: the labourers work long hours and under difficult conditions. Moreover, they are not sufficiently paid (in this case, not at all!), as the real profit goes into the pockets of the Big Boss. Everybody else just eeks out a living, but they have nowhere else to go and must survive somehow.
As to specific reference in Animal Farm, Old Major explains graphically enough during the secret meeting in the barn the manner in which they are exploited: the workhorses work overtime in the fields; the cows give their milk to the farm instead of to their young, as they are soon separated from them; most of the chickens' eggs are sold and never become chicks; the sheep are shorn for their wool, then slaughtered along with the cattle,chickens and pigs. For the farm animals, there is no respite from their labour, and often they are beaten. They go underfed unless they are being fattened up for the kill - the only deliverance they know is death. The only way "out" of this 'closed circuit' system is rebellion.
This allegory is very much like the real life distress of labourers (both agricultural and industrial) in that respect for the individual does not exist; the worker enployed is not considered a separate entity (with needs, such as a family life or personal gratification outside of a work context) but only a part of the system: his or her efficiency and contribution to general productivity are the only things which count.