The campaign, by WPP Group's 141 Worldwide/London, is targeting warm donors and focuses on the need to raise money to help find homes for pairs of dogs and avoid the need to split them up.
The mailshot features jigsaw images of one pair of dogs, Holly and Duke, with the slogan, "your kindness... will keep us together".
It goes on to tell the story of Holly and Duke whose owners were unable to look after them. The trust says that they have to re-homed together because Holly is deaf and relies on Duke to listen out for danger, but this costs more because it takes longer than re-homing a single dog.
The mail shot also includes two jigsaw pieces featuring Holly and Duke on the outside of the mailer and the enclosed reply envelope with the words "with your help, we'll always be happy together".
Steve Harding, 141 CEO, said: "Just like people dogs can become emotionally attached to each other. We decided that Valentine's Day was the perfect occasion to remind the target audience of this."
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