The Common Agricultural Policy was funded with about €400 billion in the current 2021-2027 multiannual budget, but about €100 billion has been taken from it, leaving about €300 billion.

Omissions

• The first part of the claim is approximately correct: the CAP for 2021-2027 is €386.6 billion, close to 'about €400 billion'.
• The €100 billion figure appears in discussions of the next multiannual budget (2028-2034), where the Commission proposes mobilising €100 billion for Ukraine and where over €100 billion in spending cuts, including to farm and regional funding, are under discussion.
• The €300 billion figure does not match the total CAP 2021-2027 allocation; it is closer to the first-pillar EAGF allocation (about €291 billion), so the speaker may be comparing different budget categories or misreading the split between the EAGF and the EAFRD.
• No source found shows a €100 billion reduction from the CAP within the current 2021-2027 MFF.

Sources

• PrimaryEU CAP Network — The Common Agricultural Policy: an overviewA total of €386.6 billion is available for the CAP from the EU budget (2021-2027).
• PrimaryAustrian Federal Ministry of Agriculture, Forestry, Regions and Water Management — The reform processThe agricultural budget for 2021-2027 amounts to 386.6 billion euros. ... This is 21.6 billion euros more than the European Commission had originally ...
• PrimaryEuropean Commission — EU budget 2028-2034To underpin the Union's unwavering support for Ukraine, EUR 100 billion may be mobilised for Ukraine over 2028-2034.
• SecondaryPolitico — Governments brace for €100B cut to EU budget proposalThe next long-term EU budget proposal is expected to include spending cuts of over €100 billion, including to farm and regional funding (2028-2034).