Page 67 - WSAVA2018
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GENETIC SELECTION FOR NORMAL HIPS
Studies on the response to selection based on individual phenotypes show mild improvement with hip dysplasia. It is known that the greater the selective pressure (percentage of the population eliminated from breeding due to phenotypic score), the greater the improvement. However, the greater the percentage of the population eliminated from breeding, the greater the loss of genetic diversity of the population. Therefore, selection must be combined with consideration of the breed gene pools.
The phenotypic evaluation of individual breeding dogs should be uniformly applied, and based on a properly executed hip radiograph on an anesthetized or deeply sedated dog. This allows for the best evaluation of both boney conformation and joint laxity.
Selection of breeding stock should be based on familial data – depth and breadth of hip normalcy – not just the phenotype of the individual dog. The dog’s own hip rating represents its phenotype, but the relative’s hip ratings are more representative of the dog’s genotype. For example: The individual dog’s OFA web page, and associated vertical pedigree as demonstrated on the OFA website (ofa.org) provides a good representation of the expectation of hip quality that can be passed on from the individual. A dog with excellent-rated hips but with a preponderance of fair-rated relatives would be expected to produce more like its relatives than itself.
Breaking down the hip phenotype for individual dogs allows the breeder to focus on aspects that need improvement in the next generation. If a quality dog shows some subluxation or laxity, it should be bred to a dog with tight hips. If a quality dog shows a slightly shallow acetabulum, it should be bred to a dog with deep acetabulae.
Selection based on the best available phenotypic imaging and incorporating familial breadth and depth of pedigree data should improve the hip and elbow status of individual dogs and thus their breeds.
References available upon request.
Your Singapore, the Tropical Garden City
WSV18-0277
WAVMA ORNAMENTAL FISH DISEASES
WATER QUALITY ASSESSMENT IN AQUATIC VET MEDICINE
With any animal, environmental conditions can affect their overall health, but with aquatic animals such as fish, proper water quality is an important part of a successful aquarium. Without clean water, the fish will be stressed and more susceptible to diseases and parasites. This lecture will provide veterinarians with information regarding how to test aquarium water and what the various water chemistry characteristics mean for the health of the fish. Correcting water quality problems is also included in the discussion.
Water quality can be measured with test kits available through pet stores or pond supply companies, or from many aquaculture suppliers. The simplest tests are small plastic strips with chemical pads attached that are dipped into the water to be tested. The pads change color which, when compared to a color chart, indicates the level of that substance in the water. These are fast, easy to use, inexpensive, and relatively accurate (they indicate a range rather than a precise measurement). Dry tablet tests are also available where a small tablet is dissolved into a test tube containing the water sample. Its color
is then compared to a chart to determine the results. Some test kits have liquids that are mixed with the water to produce the color reactions. More expensive test
kits use a spectrophotometer to electronically compare colors and these give more accurate results. Effective electronic meters are also available.
Ammonia:
Ammonia (NH3) in the water reduces the ability of the fish to excrete nitrogenous wastes from their blood through the gills. As ammonia increases in the water,
so do the waste products increase in the fish’s blood, causing toxicity, gill damage, and death. Ammonia is mostly converted to nontoxic ammonium (NH4+) at a pH level below 6.5, but above 6.5 ammonia can become toxic very quickly if allowed to accumulate. The higher the pH and temperature of the water, the more toxic ammonia becomes. The ammonia in the aquarium water is broken down by aerobic nitrifying bacteria into nitrite and then into nitrate. Properly operating biological filtration systems (after they have been cycled) should keep ammonia levels at 0.0 mg/L in the aquarium water.
In the event of a filtration system problem that creates high ammonia levels (>0.25 mg/L), Ammonia Neutralizing products can be used to bind the ammonia in a nontoxic form until water changes can be used to bring the ammonia level down. Failure to eliminate the ammonia through water changes will result in elevated nitrite levels a few days later.
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