Wa `alaykum as-salam wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother in Islam, thanks a lot for raising this important question, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
The concept of halal meat in Islam is not only confined to the way the animal has been slaughtered. It goes beyond that to include the way it is raised.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto,Ontario, Canada, states,
You have raised an important question. The concept of halal meat in Islam must go beyond the rituals of slaughtering to include the way the animals are raised. For, according to the Qur'anic notion of fitrah, and nature of things, the cattle aren't meant to feed on animal bits; rather, they are by nature created to be nourished by plants and grains (other than animal feed). By changing this basic nature of animals, we are distorting the creation of Allah; such is a project of Satan, as Allah has explicitly stated in the Qur'an.
We don't have to be scientists to know that when we interfere with such basic laws of nature (known in the Qur'an as sunnat Allah), we don't really know the consequences. And the questions are indeed grave as we can tell from the causes of mad cow disease!
It is therefore imperative for Muslims to look into the ways the animals are nurtured and raised in determining the criteria of halal slaughter. This is a greater priority for us, Muslims, than simple rituals of dhabihah we are obsessed with.
By considering this as an important priority, we also contribute to saving the environment and Allah's creation, for the Qur'an teaches us that our mandate is to shepherd the earth and its creatures; let us not be shepherds who burn the herd and the pasture altogether.
I commend raising this vital issue. May Allah make us all instruments of good, amen.
Allah Almighty knows best.