If an animal whose details you have saved on the Moocall Breedmanager app is no longer in your herd, you do not need to delete them from your records on the app.
Instead you can mark them as sold. Here's how you do it.
Find your animal: In the smart lists menu, press search. It is in the top left. This opens up a list of all of your animals. When you find the sold animal, click in.
Register as deceased/slaughtered/sold: In the animal's profile, you can add 'events'. Scroll down to the bottom and tap 'add other'. From here, you can press 'slaughtered', 'deceased', or 'sold'.
Look up your deceased/slaughtered/sold animal: You can find the details of the animal in herd overview menu, in the 'Historic Animal' list. These are organised by dates sold or culled.