The train ride in the work, Night, is a very symbolic moment. This is the train that the Nazi's put the Jews on and ultimately brought them to the dreadful concentration camp, Auschwitz.
Wiesel describes the train ride as a cattle ride. The Jews are put onto the trains and they can barely breathe. They are treated like animals. They are not only packed in, but they also do not know where they are going. On the train some Jews begin to flirt with one another in sexual ways. Others pretend not to notice. Then there is Madame Schächter, a middle-aged woman, who is on the train with her ten-year-old. She screams of fire outside the trains. She causes fear and finally she is beaten by some Jewish boys. After days of traveling they finally arrive at the concentration camp.
The point that Wiesel is making is that the Nazi's treated the Jews as animals. Their dignity was taken away. When this happened there were two consequences. The Jews themselves began to act like animals. Second, the Nazi could treat the Jews as animals as well. All sense of humanity was taken away. The Jews were considered cattle to be slaughtered.