From the website:
The pigs are transgenic, created by adding genetic material from jellyfish into a normal pig embryo. [...]
Taiwan is not claiming a world first. Others have bred partially fluorescent pigs before; but the researchers insist the three pigs they have produced are better. [...]
In daylight, the researchers say the pigs' eyes, teeth and trotters look green. Their skin has a greenish tinge.
In the dark, shine a blue light on them and they glow torch-light bright.
The scientists will use the transgenic pigs to study human disease. Because the pig's genetic material encodes a protein that shows up as green, it is easy to spot.
Link - via Tom Smith's The Other Blog