hi...I am including an excellent site on constipation and fibers...maybe will give you some help.
http://felineconstipation.org/prevention.html
I'm also wondering if you've tried probiotics?...my Nemo who suffered from constipation d/t a constricture in his bowel was (still is sometimes) on lactulose. for the past 3 weeks I've been giving him probiotics and his stools are no longer hard and difficult to pass....so I have my fingers crossed that this will continue to work.
If you want to try probiotics I will give you a link to the best one to use for cats and it also is the one with the most strains....I just put a small pinch in his breakfast every morning, since my local health food store doesn't carry it in the powder form, I order it from iherb. there prices are much cheaper and shipping is hassle free, they are an excellent co. to deal with (even internationally for me)
http://www.iherb.com/Garden-of-Life-Primal-Defense-Powder-HSO-Probiotic-Formula-81-g/3159?at=0
http://www.iherb.com/Garden-of-Life-Primal-Defense-Powder-HSO-Probiotic-Formula-81-g/3159?at=0
cat grass is fiber and some is good however with mega colon too much fiber will cause the colon to increase in size esp. if not emptying the bowel at least once a day. IMO a moderate amount won't cause more problems.
insoluble fiber DRAWS water into the colon and speeds up intestinal transit time, this results in a softer and larger stool. examples of insoluble fiber are wheat bran, carrots, pumpkin, zucchini, sweet potatoes, spinach and celery. the speeding up of the transit time is good for mega colon, however again you will need to be sure she empties her bowels frequently so the increase in stool size doesn't further stretch her bowel.
therefore moderation is the key.
your earlier post regarding lactulose. Its safe to give up to 2mls by dropper followed by 4mls of water, the water is very important. you can do this 2x a day. but start with just the one dose and see if its sufficient.
If I find more info on this topic I will post it for you. welcome to our forum