Goats and cattle are used in gene pharming because

Goats and cattle produce milk and are very important to mankind. They are used in gene pharming in order to increase milk and other useful products' production. Gene pharming also allows easy collection and purification of these products. Gene for overproduction or desired trait are inserted into the genes of these animals, and the proteins responsible for expression of these desired characters, are expressed.

B] nitrogen fixationmight be wrong, so correct me.want extra on your answers? just go on my account and go on questions and answer, or ask in the comments!