Cattle farming is a big contributor to the nitrate pollution. Land erosion too as well. They cause quite a lot of problems with the drinking water, for instance, methemoglobinemia. Some people may be familiar with it by the name, "blue-baby syndrome".
There's also the Cryptosporidium, E. coli, fecal coliform and Salmonella. They are found in manure and yes, they can be transferred. Heck, you can even get tetanus from touching manure or soil-based materials. All the more reasons for getting a tetanus shot.
Remember Walkerton? It was caused by the cattle farms, not a well-known fact. But that's because the cattle farmers do everything they can to keep it quiet. If you were to look into the history of problems with drinking water in several places across North America, you will discover that cattle farms were often the cause of the problem.
During the 1990s, there was a spill of manure at a hog farm. I believe it was around 20 to 25 million gallons of manure, it went into a river and killed 10 million fish. As a result, they had to close a large amount of the wetlands to shellfishing. Something like close to 400,000 acres from what I remember. I believe it took place in North Carolina. It happens quite more than people would be aware of. It's amazing how they manage to keep it under wraps.
Even the manure itself can develop dead zones in the lakes and oceans. Farms are responsible for a large number of dead fishes. Scary, eh?
It's my most favourite thing to drink, asides from water (and ok, whiskey 
