Border Collie’s failure to grow in 6 months may be caused by malnutrition or calcium deficiency. The dog needs to be supplemented with nutrients and calcium. You can feed it some egg yolks, chicken breasts, beef, carrots, bone broth and other foods. , you should also feed some probiotics appropriately to promote digestion and absorption. At the same time, the dog should be dewormed on time, otherwise parasites in the body will cause the dog to not grow taller.