8 - Breed Nutrition

1 – Retina
2 – Optic nerve
3 – Cornea
4 – Crystalline lens
5 – Vitreous humour
6 - Iris
Anatomy of the eyeball
The risks of cataracts in Cockers
Recent studies show that Cocker Spaniels are among
the breeds with a higher risk of cataracts (Adkins
and Hendrix, 2005; Gelatt and Mackay, 2005).
That risk is 2x for American Cockers and 1.9x for
English Cockers (Purdue Veterinary Medical Data
Base). There is a hereditary form that affects the
American Cocker and hereditary transmission is suspected
with respect to some types of cataract in the
English Cocker (The Kennel Club, 2006). English
Cockers suffering from cataracts have lower vitamin
C plasma levels than healthy dogs (Barros et al,
1999). This may be an indication that low-level synthesis
of vitamin C lowers its concentration in the
aqueous humour, the liquid that nourishes the eye.
Retinal disease in Cockers
Progressive retinal atrophy
Light rays enter the eye through the pupil, passing through
the crystalline lens before converging on the retina. The light
Progressive retinal atrophy (PRA) is a hereditary
information is then transmitted by the optic nerve to the brain
disease that can gradually evolve towards total blind-
where it is analysed. If the crystalline lens is opaque the rays will ness. Compared with the average population, the
not be able to reach the retina.
risk of PRA is said to be 45 times greater in the
English Cocker (Dorn et al, 2001). The most widespread
form of PRA in the Cocker is however the
degeneration of the rods, the retina’s photoreceptors, which are specialised in mesopic vision. The
first clinical signs generally appear between three and eight years (Chaudieu, 1997). The dog seems
to be disoriented at night or is hesitant about entering a dark room. There is a genetic screening test
for English Cockers, while one is said to be in development for American Cockers. This disease is
thought to be linked to a primary deficiency in vitamin E, which is liable to develop even when the
level of vitamin E is in line with common nutritional recommendations (McLellan et al, 2002).
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