Researchers attempted to find out how chlortetracycline, when given to pigs, impacted the pigs bone color and bone density. Pigs were either put on a diet that consisted of no chlortetracycline or with 800ppm of chlortetacycline. The pigs started on the diet at either 28 days old or 84 days old. Pigs were put on the diet for either 28 days or 56 days. Discoloration of the lumbar vertebrae and bone density were assessed from randomly selected pigs every 28 days until the pigs reached 168 days of age. The longer the pigs were held on the medicated diet and the older they were when put on the diet, saw increased chances of bone discoloration. Bone density improved the longer the pigs were held on the medicated diet. The researchers concluded that the bone discolorationon was reversable and application of the medicated diet caused permanent bone density improvement.