We try to deworm in spring and fall, due to the heat being the main reason, but if they need it and are in poor condition give it to them, regard less time of the year.
Injectable vs. pour-on
Pour -on was developed out of the way of convince for the producer. Personally I would use inject able for these reasons.
1. When you inject the dewormer Subqtanilly you know that it is in there.
2. I don't want anything that could penetrate a cow’s tough hide to be near my skin.
3. With pour-on you tend to waste some
4. Also with pour on they need to be fenced out of a pond or creek for a while.
But you do what is best for you and your operation. Answer these questions and they will tell you which is better suited for you.
What type of facility do I have?
What is the behavior of my herd? Calm or wild as a buck
How much time do I have?
If you have a good facility disregard the behavior question an use the injectable, but if you just have an ok facility and some nervous cows you might look at pour-on. The best advice I can give you is try it both ways and with the experience you will be able to decide which is best for you.
Best of Luck