Ask the Doctor . . .Dear Dr. Meek:
Can you comment on acquired cataracts in the Mastiff? Our puppy, and her litter brother, were hand-raised and both have cataracts in both eyes. They seem to see fine, and we were told that the eyes may improve. What causes this? How can it be avoided in hand-raised puppies?
Kris & Sheryl Garrison
Wilton Manors, Florida
The following was originally prepared as an article for the Reporter by Dr. Meek, but since it so aptly answered the question from Kris & Sheryl Garrison, we have included it here.
By Dr. Lisa Meek, Member ACVO
A nutritional cataract is caused by either a deficiency or excess of a nutrient resulting in a loss of transparency of the lens. Nutritional cataracts have been identified in various species, including rats, pigs, wolves, fish and guinea pigs as well as dogs and cats. In dogs and cats the most common cause of nutritional cataracts is being hand raised on milk replacer.
It is usually possible to differentiate nutritional cataracts from inherited cataracts. The location of the cataract within the lens is fairly unique compared to other cataracts. The cataract is present within a few weeks of starting milk replacer. When combined with a history of being hand raised, the diagnosis is usually straight-forward. Also, inherited cataracts rarely occur at such early ages (with a few exceptions).
Nutritional cataracts usually do not progress to interefere significantly with vision. Some will improve with age, as the young lens has some ability to repair itself. The younger the pup is when switched from bitch to hand raising, the more likely it is to develop nutritional cataracts. Also, the sooner it is started on solid food, the sooner the lens can stabilize and improve.
Numerous studies have been performed to try to identify specific causes of nutritional cataracts. Most studies have implicated abnormal amino acid levels, with the specific amino acid implicated varying from species to species. Arginine deficiency has been implicated as the most likely cause of nutritional cataracts in dogs. Most of the commercial milk replacers do not contain added arginine. One exception is Nurturall by VPL. All of the commonly available milk replacers (Esbilac, Havolac, Unilact, Veta-lac, and Nurturall) have lower protein levels than bitches milk. Bitches milk has approximately 10.7% protein, cows and goats milk 3.5% protein, and the above mentioned supplements range from 4.5% protein to 7.5% protein.
There have been no studies evaluating home made diets, but it is known that meat is a good source of arginine. Therefore, one of the most common recommendations has been to add beef or liver baby food to the milk replacers. Since no studies have been performed evaluating this combination, there are not specific recommendations as to how much baby food should be added.
The specific recommendations that I can make are the following:
(Ed. Note: Recent ads in the AKC Gazette also show "Just Born" milk replacer as having the arginine added and the protein content of this product is also 7.5%. Nurturall is available from Veterinary Products Lab in Phoenix, Arizona (800) 548-2828 and Just Born is by Farnam, also in Phoenix (800) 234-2269).