How to judge the age of a Border Collie? The age of a Border Collie can be judged by the development of its teeth. At 30-40 days old, the deciduous incisors are all in full length; at 2 months, all the deciduous incisors are all in full length, pointed and tender white. At 2-4 months, the first deciduous incisor is replaced; at 5-6 months, the second and third deciduous incisors and all deciduous canines are replaced.

Over 8 months old, all teeth will be replaced by permanent teeth. At 1 year old, the permanent teeth are all long, smooth and strong, with sharp protrusions on the upper part of the incisors; at 1.5 years old, the peak of the first incisor tooth of the mandible disappears. At 2.5 years old, the peak of the second mandibular incisor disappeared.

At 3.5 years old, the peak of the maxillary first incisor was lost. At 4.5 years old, the peak of the maxillary second incisor was lost. At the age of 5, the peak of the third mandibular incisor was slightly worn, and at the same time, the first and second mandibular incisors were ground into a rectangular shape. 6 years old, the peak of the third mandibular incisor is obliterated and the canine teeth are blunt and rounded;

At the age of 7, the first incisor tooth of the mandible was worn to the root of the tooth, and the wear surface was vertically oval. At the age of 8, the first incisor of the mandible was worn and tilted forward. At 10 years old, the wear surfaces of the second mandibular and first maxillary incisors were longitudinally oval in shape. At the age of 16, the incisors were lost and the canines were incomplete. 20 years old, canine teeth lost;

Adult dogs are quite big. The Border Collie itself is a large dog, with a length of about 55-61 centimeters and a weight of about 26-31.5kg for male dogs and 25-27kg for female dogs.