What do Banjaman and the others realize as boxer is being taken away?

The hopeful animals wish Boxer goodbye, but Benjamin breaks their revelry by reading the lettering on the side of the van: “Alfred Simmons, Horse Slaughterer and Glue Boiler, Willingdon. Dealer in Hides and Bone-Meal. Kennels Supplied” (123). The animals panic and try to get Boxer to escape.