Dogs in puppy mills often suffer from an array of painful and potentially life-shortening veterinary problems due to overcrowded, unsanitary conditions and the lack of proper oversight or veterinary care. Conditions common to puppy mills, such as the use of stacked, wire cages to house more animals than a given space should reasonably hold, as well as constant exposure to the feces and urine of other dogs, make it difficult for dogs to avoid exposure to common parasites and infectious diseases. In addition, a lack of regular, preventive veterinary care, clean food and water, basic cleaning and grooming, and careful daily observation by the operators may cause even minor injuries or infections to fester until they become severe. These disorders cause undue pain and suffering to the animals involved and often result in premature death.
The Humane Society of the United States, "Veterinary Problems in Puppy Mill Dogs" (2012). PUPPY MILL REPORTS. 7.