An-225, why do you have to bring your Clintonite political ideas into every single thread in this forum?
Cattle do indeed usually lie down to sleep, but they are often so domesticated that they are easy to approach (cattle are not the brightest of animals...). Tipping one over might be possible for a strong person.
As Voyager noted, it can be dangerous for the animal, so please don't do it. Vets are very carefull to give animals low enough doses when using tranquiliser darts that the animal has time to lie down and go to sleep. This is for a reason!
Those are expensive animals, a grown cow can cost a farmer tens of thousands to replace if she has to be put down (lost income, bringing up a new calf, etc.), a bull even more.
Cattle are also unpredictable, some may be safe to approach, others are extremely dangerous and you cannot tell in advance unless you know the individual animal well.
I wish I were flying