The blocks are nutritionally complete, but are highly processed food and would be boring to eat all the time.
Nutrition is better if it comes from real, unprocessed or minimally processed foods - eating food is a much better, more complete way to get the vits you need and I have read they are better absorbed from food, then taking a vit.
So rats will survive on just blocks.
To be healthy and also to lower the % of protien in their diets (even blocks with 14% protien have way too much protien for rats), rats need daily vegs
A variety of vegs in the diet is good as different vegs have different nutrition (vits, minerals, etc), variety adds different textures and different tastes.
Vegs and whole grains and seeds etc not only provide nutrition but also provide fibre
Some, but not a lot of cooked whole grains and fruit and seeds are important to have in the diet for the same reasons as daily veg. In addition, many people like to give their rats treats, and it is important to give them healthy treats such as berries or seeds instead of processed foods that contain sugar (feeds cancer), salt, preservatives, and various chemicals.
Vegs, whole grains, seeds, etc have many health benefits such as helping to prevent cancer. You do not get these benefits from processed foods, incl their blocks
The reason it is recommended to feed blocks is because no one has yet come up with a whole food diet (vegs, grains, fruit, seeds, etc) that will meet all of their nutritional needs.
Blocks are also convenient and inexpensive compared to a healthy whole food diet.
When you feed a low protien good quality block (oxbow, Harlan Teklad 2014), you know that they are getting what they need, so you do not need to worry about it and can supplement their diet as much as possible with healthy whole foods.
I give vegs once or twice a day and fruit once a day - such as a piece of ripe banana or some wild blueberries (I buy them in season and freeze so they can enjoy them all year) on cooked whole organic 12 grain cereal or oatmeal.
If you saw the way my ratties came racing to me last night to grab a piece of cooked organic corn on the cob (in season from the local farmers market) or the way they love their organic baby kale, broccoli, and organic mixed greens, organic pumpkin seeds etc you would understand what a difference real whole food makes to their quality of life.
As for veg amount, I believe that Jorats suggests to give as much as they will eat in 20 mins, and then remove the excess. As for types, well different rats like different things so you would need to offer small amounts several times to see if they like it (rats will try a tiny amount of a new food and if it does not make them ill, next time they will try a bit more) ……. they will have their favorites but will likely enjoy most types of vegs, grains, and fruit - but keep the forbidden foods list in mind.
If you are interested in nutrition:
nutritionfacts.org
http://ratfanclub.org/nutreq.html
https://cronometer.com/
https://www.sciencedirect.com/science/article/pii/S1550413114000655
https://nutritionfacts.org/video/dr...l&utm_source=facebook.com&utm_campaign=buffer
I hope this info helps
