Besides the variety and the management, the main reason is feedfactor.
而奶牛单产低的原因除了品种和管理外，主要就是饲料因素。
2
Another factor is the squeeze that conventional dairy farmers have felt as the price of grain they feed their cows has gone up, tightening their profit margins.
另一个因素是，传统的奶农在他们喂养奶牛的谷物价格上涨时感到了压力，他们的利润空间也被压缩。
3
Furthermore, in the effort to feed the hosts of people on this planet, the focus on factory and intensive farming methods is being cited as a key factor in climate change.