DÃ rflein had to sleep on a mattress next to the cub at night because Knut needed care . DÃ rflein also had to play with , bathe , and feed the cub every day . Knut 's need for round-the-clock care required that DÃ rflein not only sleep on a mattress next to Knut 's sleeping crate at night , but also play with , bathe , and feed the cub daily .