There is one important thing about that video. Did you notice that these are all dairy cows? Yes, that company specializes in processing dairy cattle for meat, but why so many dairy cows and why are they in such bad shape?
While possible disease like mad cow can only be ruled out with a blood test, there are other reasons that dairy cows end up like this. Basically, they get worn out. The whole "happy cow" thing is a myth for the majority of these animals. From the Humane Society's site:
This is one of the many reasons that I pay more for local milk from grassfed cows, who are not given hormones. The choice is one that I know is best for the cows, and, very likely a much healthier choice for my family. I hope that this type of natural dairy sees a return to more local food systems so that we all can have a better choice.
In addition to breeding them for astronomical rates of milk production, producers often inject cows with hormones to further increase their unnaturally large milk yield. One animal scientist compares the modern dairy cow's metabolic stress stemming from hyper-productivity to a human jogging six hours a day, every day. Dairy cows are milked for ten months a year (including seven of their nine months of pregnancy) until their worn-out bodies begin to give in and they're slaughtered. Approximately 15 percent of the hamburger meat in the United States comes from "spent" dairy cows.
Although cows can live to be 15 or even older, they're typically slaughtered around four years of age. And as The HSUS's investigation revealed, dairy cows who are too sick or injured to walk to their own slaughter ("downers") can endure terrible abuses.