If your cows produce discolored urine when fed on avocados, then stop feeding them.
There are cows feeding on avocado leaves and fruits with no side effects, except choking when they swallow the seeds.
Avocados contain a chemical known as persin, which is responsible for most of the side effects seen when animals (including cows) consume large quantities.
All parts of avocado trees contain the chemical.
Some farmer have reported mastitis (leading to reduction in milk production), weakness, skin color change, exercise intolerance, difficulty in breathing and death in severe cases
There is no known amount of avocado one can give to the cow to have side effects and this could be due to variance in immune response in cattle, different varieties of avocados and parts consumed.
If you can avoid it in your rations, the better, but if you must, use small amounts.