The UK has had problems trying to get the EU to raise its minimum animal welfare standards. We have lost a lot of agricultural output to cheap imports from the continent.
The UK rightly imposes higher standards in some cases. For example, we ban sow stalls completely where the EU allows them for four weeks of use.
The EU allows the export of live animals within and outside the EU, permitting long and unregulated journeys beyond its borders.
When we leave the EU we will be free to set our own standards, which will be higher than EU minimum requirements. This makes animal welfare an odd argument for people to use who want us to stay in the EU system.