As noted in previous posts regarding Cosmo's food, I have used Royal Canin Urinary SO (moderate calorie) canned food as an oxalate-free source of vitamins and other essential nutrients that are below the RDA in his homemade food recipe. In many ways, I am using the Urinary SO as one would use a "Balance IT" additive. One of the problems with an oxalate-free diet is that green leafy vegetables, as well as some root vegetables, cannot be used. These are good sources of vitamins and minerals. Using the Urinary SO gets around that problem and limits the number of chemical additives I have to use.
Recently I discovered that Royal Canin changed the formulation of their Urinary SO (moderate calorie) canned food. For the most part, the new RC recipe is an improvement since it has less fat (47% old vs 26% new); however, it also has fewer calories per gram (0.9 vs 0.8%) and each can contains fewer calories (326 vs 282) which makes it is even more expensive. It is interesting to note that Royal Canin did not effectively notify consumers of this change and the new label does not declare any change in the formulation (e.g., no statement like "new improved formula"). Of course, some of the changes are shown in the nutrition data provided on the label. It just does not jump out at you that there has been a significant change.
One reason I used the Urinary SO in the past was that the company provided a rather complete list of "typical analysis" data for the various nutrients in the food. This made it easy to well define this food in PDD. I contacted RC and they sent an abbreviated list (41 ingredients old vs 24 new) for the new formulation. Fortunately, it included most of the nutrients of concern. So I adjusted the Urinary SO "food" in Pet Diet Designer so that it reflected the new analytical data. I assumed that the amounts for the nutrients for which I didn't have analytical data had not changed significantly. I continue to use 125 g per day of the Urinary SO in Cosmo's food which now only contributes about 100 calories of his daily 572 calorie requirement (17.5% of calories).
Given that the Urinary SO now contains less fat and fewer calories I had to make some changes to the homemade recipe with the help of PDD. The balance screen for the new recipe is shown below. I added some corn oil to bring up the fat content and calories. I also increased the turkey and bone meal and reduced the amount of rice by small amounts. The end result is a recipe with a similar protein, fat and carbohydrate content (as a percent of calories) to the previous recipe. See the PDD nutrient report below.
Since the Urinary SO now contains less zinc, I decided to add the contents of one zinc sulfate 220 mg capsule to the 21-day batch recipe. As I have mentioned previously, nutritional supplement capsules, which are meant for human consumption, provide a good source of many minerals and vitamins for homemade pet food. They are relatively inexpensive and do not require accurate weighing of small amounts of the additive. And if one uses a bulk chemical as an additive, it is usually necessary to calculate the amount of the specific nutrient in the chemical, e.g. the amount of zinc in bulk zinc sulfate. This information is almost always given on the label of a supplement capsule (e.g., 50 mg of zinc in 220 mg of zinc sulfate).
Defining a supplement capsule with the PDD food wizard can be tricky. Using the zinc sulfate capsules as an example… when using the wizard pick the common measure rather than the per 100g choice. Define the amount as "1" (for one capsule), then define the measure as "capsule." The "measure weight" is the weight of one filled capsule. Normally I weigh 5 or 10 capsules together to get an average weight for one capsule. Once this is done, I enter the amount of zinc in one capsule which is 50 mg (from the label). Note that it is not 220 mg which is the weight of zinc sulfate in the capsule. Then I save and close the wizard to complete the zinc food entry. Be sure to hit "refresh" before searching for your new entry in the food database.
When you go to enter the new capsule ingredient into your recipe (balance screen), PDD will initially enter it as 100g of capsules. But on the far right of that entry, there is a drop-down menu that allows you to select capsule rather than grams as the unit of measure. I find it easier and clearer to work in "capsule units." Once you select capsules and adjust the quantity to give the correct amount, go back to the recipe and refresh it to bring the new ingredient into the recipe. Then save it. If you do the refresh before changing the balance screen from grams to capsules, the recipe will show grams of capsules in the batch report and I don't think there is an easy way to change this. That is not a big problem. Just weigh out the amount of capsules needed but remember, the weight is in terms of filled capsules, not the powder in the capsules.
If you use the unit of measure as capsules, the balance screen will usually show a fraction of a capsule for the daily amount. But the batch, which for us is a 21-day supply will show a more usable value. I don't worry about getting it exact. I just round up or down as needed. For example, the batch recipe states that 5.25 capsules of copper citrate are needed but I just use the contents of 5 capsules. To empty the capsule, just pull it apart. Wearing surgical gloves of some sort helps grip the capsule ends. I discard the empty capsules and mix the emptied powder well into the recipe. As can be seen from the recipe, I use capsules to supplement the other foods used with potassium, magnesium, zinc, iodine, copper and fish oil. Note from the balance screen that the RDA is not met for zinc even with the addition of one capsule of zinc sulfate. Since it is a new ingredient and zinc sulfate can cause stomach upset, I tried adding just one capsule for the first batch. I have not seen any problems and will add two capsules the next time around. That amount will exceed the RDA for zinc.
We continue to give Cosmo "soup" three times a day to dilute his urine and hopefully decrease the chance of oxalate stones forming. See the previous posts for more information on this. The new recipe also continues to use citrate to make his urine less acidic which is also thought to inhibit stone formation. So far Cosmo really likes the new Royal Canin food and only leaves a few rice grains in his bowl (and on the floor!).