Brindle is dominant over solid colour, other than black, which may no longer exist as a Mastiff colour. Apricot is dominant over fawn, though that dominance may be incomplete. Most of the colour faults are recessive, though black is so rare in the Mastiff that it has never been determined whether the allele is recessive or a mutation that is dominant. (Note that this 'C locus' may not be the same as the one identified in other animals, SLC45A2.) However, regular exercise must be maintained throughout the dog's life to discourage slothful behaviour and to prevent a number of health problems. A soft surface is recommended for the dog to sleep on to prevent the development of calluses, arthritis, and hygroma (an acute inflammatory swelling). Due to the breed's large size, puppies may potentially be smothered or crushed by the mother during nursing.
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