When a chicken doesn't or cannot eat by herself, we may need to intervene. The safest way to feed her is to put food directly in her crop. Tube feeding is pretty simple but may be scary the first time you do it. If possible, have someone who knows how to do it mentor you the first time.
Here is what you need:
* food (I use the recovery formula from Harrison's Birds Foods)
* one 60ml syringe
* one tube with a mark at 6" from the end for a standard size chicken (I use a Feeding Tube/Urethral Catheter (14 Fr) from Covidien)
Here are the steps:
1) the crop must be empty
2) gently stretch her neck
3) open her beak
4) put tube on top of the tongue, make sure to not push the tongue down the throat
5) push slowly tube inside until you reached the mark, there shouldn't be any resistance (if there is any, remove the tube, take a break, and start again)
6) push food inside crop, use your body weight
7) once syringe is empty, pinch the tube (so no food goes in the trachea) and remove the tube
Weigh your chicken to make sure she eats enough and doesn't lose weight. I am giving Curry 60ml of food 3 times per day.