Your Border collie is breathing hard because he/she might be in pain or having fever. Normal causes of heavy breathing in dogs are exercise and hot weather. Dogs also have difficulty in breathing when not getting sufficient oxygen. Some common causes of lack of oxygen can be
1. Heartworm
2. Heart diseases
3. Lungs diseases
4. Trauma
5. Pneumonia
6. Fluid in lungs
7. Bleeding in lungs
8. Obstruction of air passage
So, your dog needs to be investigated by the vet to know cause of heavy breathing and treatment. This can be done by taking him to vet.
1. Heartworm
2. Heart diseases
3. Lungs diseases
4. Trauma
5. Pneumonia
6. Fluid in lungs
7. Bleeding in lungs
8. Obstruction of air passage
So, your dog needs to be investigated by the vet to know cause of heavy breathing and treatment. This can be done by taking him to vet.