They give it to cattle before slaughter to beef them up. Theres your answer right there.
doing some reading on the cattle use and my impression was it was for the sparing effect once their already beefed up... since there is various blends with most containing various doses of estrogen, the higher dosed estrogen blends are used further out from slaughter for the beefing up and the closer they get to slaughter they taper down the estrogen and leave the tren high or raise it higher since feeding is restricted the closer they get to slaughter due to transporting and staging for market sale etc
doing some reading on the cattle use and my impression was it was for the sparing effect once their already beefed up... since there is various blends with most containing various doses of estrogen, the higher dosed estrogen blends are used further out from slaughter for the beefing up and the closer they get to slaughter they taper down the estrogen and leave the tren high or raise it higher since feeding is restricted the closer they get to slaughter due to transporting and staging for market sale etc
of course due to its effects on the thyroid and raising of IGF1 it would also promote muscle building as nothuman stated...
That totaly depends on what is heavier , a pound of lead or pound of feathers?