Treating constipation involves trial and error and the condition often benefits from a combination of treatments.
Generally speaking, all constipated cats will benefit from an increase in fecal water content but the main question is: Do you want to increase fecal bulk (increase in diameter) with a soluble fiber?
No, Usually not a good idea. However, as noted above, there is evidence to show that soluble fiber has other beneficial effects on the colon.
Therefore, you may want to add a small amount of soluble fiber into the diet, in addition to using Miralax for constipated feline patients.
In the ‘old days’ megacolon cats (cats with abnormally large colons with compromised motility) were routinely treated with high fiber diets. Unfortunately, many of these cats had their constipation worsen because their compromised colon could not handle the bulky stool.
But as the saying goes, “the devil is in the details” or, in this case, the dosage. While too much fiber (or the wrong type of fiber – INsoluble vs soluble) may be detrimental, a lower dosage of the correct type of fiber (soluble) may be beneficial. This is true for megacolon cases as well as the average cat with a reasonably healthy gut tract experiencing a bout of constipation.
When treating constipation in cats, monitor the diameter of the feces, as well as the moisture content to determine which treatment – and dosage – works best for your cat.
To repeat: We are not looking to create a large, soft, stinky poop by using too much fiber!