Only when they are molting.
The food they need is commercially called Layer Formula/Laying mash or Layer pellets This food has the extra Protein,calcium, minerals and vitamins needed for good egg/shell production.
Extra protein and carbs
Having extra protein in your body merely provides a stockpile of fuel/food for potential muscle growth, but you need to work the muscles. Without the work, the extra protein gets you nothing.
In real life, yes, a horse at work will need more protein than he will when not at work. Not exactly... You just have to make sure that they are getting the amount of food needed. On Howrse you can't give them 'extra protein'!
Albumen
Cornish hens do not need a specialized feed. You would feed a Cornish hen the same as any other breed of chicken. A good quality commercial layer feed if she is still young enough to lay eggs. Scratch feed of mixed grains if she does not need the extra calcium or protein for egg production.
most people use whey protein for weightlifting, however you can use it for any kind of exersize if you need the extra protein
If you only have hens then no it is not possible. You need a rooster with the hens to get an embryo.
stick with daily nutritional amounts. you could drink protein/ whey drinks as well.
Hens do not need grass to lay eggs if their food contains all the nutrients they need, but they do enjoy eating it!
You only need 1 roaster for every 10 hens. So if you say you have 150 hens than you will need 15 roasters.
No. Having a rooster in with the hens is a natural situation and has no other health concerns than having one extra chicken in the flock.