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Susie's
Water/Dry Matter Ratio |
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Introduction | Calculating | Benefits & Limitations | Graphs - Intro | Page 2 (Graphs)
Introduction
When Susie first became diabetic, I began looking at ways that I could use to monitor her condition. I decided quite early on that it would not be good to measure Susie's blood glucose at home, so I was left with measuring her urine glucose and trying to measure how much water she was drinking.
Weighing her water was easy enough. I would fill her bowl, weigh it full, weigh it again when changing it, and the difference was the water she had drunk. However, I quickly realised that if this was going to be meaningful, it had to take account of a couple of other factors:
- The water or moisture content of her food - typically 80% in moist foods (pouches, trays, cans etc) but less than 10% in dry foods
- How much food she was eating - the more she eats, the more she needs to drink
This led me to the concept of calculating the ratio of total water to dry matter.
How I Calculated the Ratio
It can seem a bit complex at first, but it is really quite simple. It all hinges on weighing all of her food and drink.
I weighed all of her food and water bowls in exactly the same way. I filled them with fresh food or water, weighed them full and them weighed them again when removing them. The difference was the amount that Susie has eaten or drunk. Then there was the calculation bit:
Total water includes the following:
- all the water that Susie has drunk from her bowls
- the moisture or water present in her moist foods (typically 80%)
- the moisture or water present in her dry foods (typically 8%)
Dry matter includes the following:
- the solid food content of her moist foods (typically 20%)
- the solid food content of her dry foods (typically 92%)
Calculating the Ratio:
- For each 24 hour period, I simply divided Susie's total water figure by her dry matter figure to give the ratio.
- With the help of a spreadsheet it was very simple to do, but even with nothing more than a calculator, it was not too onerous.
- I also used the spreadsheet to help graph the results over a suitable period (3 months).
Typically, when Susie was first diagnosed, her ratio was about 7 (i.e. 7g total water to every 1g of dry matter). This dropped to between 2 and 3 when she was fully stabilised. More recently, in 2004, there was a sudden and unexpected change in her drinking which was unrelated to diabetes. Since then, her ratio had been about 6.
Benefits & Limitations
All monitoring techniques have their own benefits and limitations, and I firmly believe that it is important to take a broad view using as many indicators as possible. From my experience of using this ratio as one of Susie's indicators, I would summarise the main benefits and limitations of this method in the following way:
Benefits
- I found it to be hugely useful when Susie was first diagnosed in 1999. For some time, this ratio was the only means I had of seeing that Susie's diabetes was starting to be brought under control. I had seen a sustained drop in her ratio long before any reduction in her urine glucose was detectable with Keto-Diastix. This gave me some very important early reassurance.
- During periods when Susie had been on a mixed diet (dry and moist foods) or on exclusively moist foods, it was almost impossible to get a feel for the amount of water she was taking in simply by weighing her water bowls. The ratio cut through all of that. This point was really brought home to me in November 2005 when I had to change Susie's diet completely. Prior to then, she was on exclusively dry food. Even though I had to change her on to a moist food diet, her ratio remained the same. This confirmed to me that everything was still in balance and that the change of diet was successful. A graph of this period is shown on the next page.
- I also found this ratio to respond significantly to a single missed injection and to periods of reduced insulin dosages. This was useful learning, because my instinct when Susie was ill and not eating was to stop her insulin altogether. It was far better to continue with a reduced dosage and increase it back to normal as she recovered. As always, this had to be done carefully balancing it against the risks of hypoglycaemia.
Limitations
- Natural day to day variations can make the graph look a bit "noisy" or variable, but it is important to look beyond these variations and focus on real trends over a period of time.
- For some years Susie was on a diet of exclusively dry food and her diabetes was generally very stable. During that period I found it unnecessary to calculate her ratio. With so little variation in the amount of food she was eating, and with such a low moisture content, it was simpler at that time just to look at how much water she was drinking from her bowls.
Graphs
As mentioned above, calculating this ratio on a spreadsheet makes it relatively simple to view the figures over a period of time on a graph. Some examples of graphs that I have produced for Susie over the years can be seen by clicking here.
Important note: All information and opinion in the Susie, Diabetic Cat pages is from personal experience. Nothing in these pages is intended to be a substitute for proper professional advice, which should always be sought from a qualified veterinary surgeon.
This page
was last updated
May 2006