Since the last century, animal testing is going on. (Your tense here doesn't make sense; "since" is past, "is" is present. Decide which you want and then stick with it.) Animal testing is a test done by the researchers in the laboratories with animals. Some people believe that it is a cruel and inhumane practice. While others believe animal research is needed to advance, especially in the medical field, also important in improving human health. Deaths through research are absolutely unnecessary and are morally no different from murder. When locked up they suffer tremendous stress. Can we know they do not feel pain? However, animal testing has helped to develop vaccines against diseases like rabies, polio, measles, mumps, rubella and TB. Operations on animals helped to develop organ transplant and open-heart surgery techniques. So in our new technological society, I believe that animals should only be used for research when absolutely necessary. (Watch random and inappropriate capitalization.)
Because animals are like humans. There is no doubt they experience a life. Like us, animals can feel pain and fear, but also excitement and satisfaction. Certainly animals do not have abilities as humans like talking, driving cars, or writing books. But regardless of intelligence, their life still has value to them. Exactly same is true of animals. (This is a redundant sentence; you just finished writing about how they have feelings but not the cognitive development humnas have. If you are not speaking about animals, who are you speaking about?) Animals are having stress (Tense; are you going to write this essay in past or present tense?) , when they are used for research including artificial marking and tagging procedures for biomedical and wildlife experimentation. The US department of the Agriculture livestock behavior research unit's Dr. Heng-Wei Cheng and graduate researchers Rachel L. Dennis and Alan