Some are chained to the walls or floors of their enclosure for the duration of their lives. They are artificially inseminated and they must suckle their young through the bars of the stall until they are cruelly taken away after a short time. If we truly are a caring species, then our compassion must extend to the other sentient beings who inhabit our planet. Battery hens are kept in tiny cages and can't even spread their wings. They are often debeaked, as chicks, with a hot wire guillotine.
Pigs suffer in the most appalling conditions to satisfy the bellies of humans.
Please know with certainty that there has never been any major scientific advances achieved through testing on animals. There ARE alternatives to wearing animal by-products, and you WON'T die if you do not eat your 'meat'. Not only will you not die if you give up meat eating, you will find that you feel MUCH better. There's a wonderful lightness of being and you will find that all of your bodily functions will improve. We all want a world with less strife and more compassion.