My partner won't compromise?

We just brought a house together, been with each other for 6 years.

I am a huge animal lover and I have pets at home, cats, dogs, rabbits and guinea pigs that me and my mom raise.
When we brought the house my mom said she will pay for the food we get (big bag of food shavings etc…) and we can just use hers if I want to take s couple of the guinea pigs with me as we may struggle for money at the start and she doesn't mind as she buys the food and the shavings etc, every month anyway.

I told my boyfriend this and he said no I'm not taking any, even though it's a joint mortgage and the shed is already build in the back garden and the animals won't cost us a penny, I'll just have to maintain them myself which I love and have time for, I feel like he's not giving up anything for me but I'm expected to give up things for him, advice please?

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