elipses in comparisons

[capnx]

in SC 1000 #32, the correct answer reads:

A study commissioned by... showed that if calves excercise and associate with other calves, they require less medication and gain weight more quickly than those raised in confinement.

so essentially the comparison reads:
They require less than those.

why is the second "require" omitted? Why not:

They require less than those require or
They require less than those do

Is this not the same as in the case:
French wines taste better than Australian wines do.

slightly confused here. Please give the governing principle for this one. Thanks

[heshamelaziry]

in SC 1000 #32, the correct answer reads:

A study commissioned by... showed that if calves excercise and associate with other calves, they require less medication and gain weight more quickly than those raised in confinement.

so essentially the comparison reads:
They require less than those.

why is the second "require" omitted? Why not:

They require less than those require or
They require less than those do

The comparison here is between "calves" so "do" is not needed here. However, the second part is intimedating for us to put calves, but "those" work the same as calves

Is this not the same as in the case:
French wines taste better than Australian wines do.

slightly confused here. Please give the governing principle for this one. Thanks