This is a very serious situation and requires immediate veterinary assistance. Trying to assist a cow in labor yourself can be extremely dangerous for both the cow and the calf, and can even result in injury or death.
Here's what you should do immediately:
1. Call a veterinarian. This is the most important step. A vet can assess the situation, determine the best course of action, and provide the necessary assistance.
2. Observe the cow closely. Note any signs of distress, such as excessive straining, restlessness, or bleeding.
3. Do not attempt to pull the calf. This can cause serious injury to both the cow and the calf.
4. Keep the cow calm. A calm environment can help her relax and make the birthing process easier.
Remember, a breech birth is a medical emergency that requires professional help. Waiting for a vet to arrive could mean the difference between a healthy calf and a tragic outcome.