Well known that pedigree dogs typically have a shorter life expectancy and worse health
than that of their cross-bred counterparts - pedigree dogs are more in-bred
Cross bred animals have a higher chance of displaying "hybrid vigor" - making them more
functional due to beneficial (diverse) genetic contributions from both parents
Breeds displaying a severe prevalence of inherited conditions are
often descended from very few animals = small founding
KCCS - Thought to descend from only 6 dogs
Rusbridge and Knowler, 2003
Line breeding
Commonly practiced in the dog breeding community - keeping lines "pure" by continually
mating a handful of successful animals which share a common ancestor = greater chance of
replicating desirable characteristics
Line breeding reduces genetic variability and
prevents hybrid vigor from occuring in most
matings
Using popular sires also
dramatically reduces genetic
variability
Due to line breeding, of the 45,000 Boxers surveyed in
the UK, all could be traced back to only 45
breeding dogs
Calboli et al., 2008
Often, by selecting for a select gene another seemingly un-related gene is
also promoted - Dalmatians black patches promotes high uric acid that can
contribute to urinary disorders
Out-crossing to increase genetic variability and reduce
heritable conditions
For example: Dalmatian out crossed with a Pointer, then back in to Dalmatians that
didn't have a heritable disorder (high uric acid) = progeny without genetics for the
disorder
The KC will only register the 5th generation of
these out-crosses however = breeders are put off
Rooney and Sargan, 2009
Many perspective owners will buy dogs
based on their pedigree - believing it indicates
quality = promotes further pedigree breeding
Morphological extremes
Large head - dystocia
C-section often required
Females have no
limitations on number of
C-sections allowed
Short legs & long backs - limited locomotion &
predisposition to spinal issues
Disc prolapse & subsequent spinal cord compression
- pain, weak back legs & eventual paralysis
Singh and Masuda, 2005
Large, heavy set breeds - joint issues
Osteochondrosis - death of bone cells growing too
quickly for blood supply to function effectivly
Limits mobility - lameness from an early age
Can cause secondary damage - often permanent
PAINFUL.
Ekman and Carlson, 1998
Hip/ elbow dysplasia
Malfitting of bones into joints and surrounding tissue too weak
to hold in place- erosive change of joint/ dislocation occurs
PAINFUL - often progressive through the creation of
arthritis
Brachycephalic - respiratory issues
Elongated soft palette interferes with air
passage into the trachea
Monet, 2004
Dogs commonly cause secondary damage to
larynx when attempting to breath (forced) which
can lead to laryngeal collapse
Stenotic nares- shortening of the nostrils
reduces air inspired
Surgical opening of the nostrils and
ressection of soft palate VERY common to
allow for more normal exercise
Reduced area for evaporation when
panting - prone to heat stroke