究其原因是现代生产工艺限制了猪群的某些行为习性，使猪的抗逆性、抵抗力和免疫力下降，造成对环境的要求越来越严。

The reason is that the modern production technics limit some behavior habits and decrease the resistance and immunity, so the require for environment become more and more severe.

youdao

究其原因是现代生产工艺限制了猪群的某些行为习性，使猪的抗逆性、抵抗力和免疫力下降，造成对环境的要求越来越严。

The reason is that the modern production technics limit some behavior habits and decrease the resistance and immunity, so the require for environment become more and more severe.

youdao