You should not apply forced feeding to any (healthy) animal.

@Mr kan, I was advised by my adviser to follow Sibbald's (1976) method for the digestibility of the investigated feedstuff. Is it alright in this matter? 

I have always had objections to the Sibbald method (like quite a lot of European poultry scientists). Not only objections from an animal welfare point of view - which is much more prominent nowadays than 40 years ago- but first and foremost from a physiological point of view.

I am not convinced that during forced feeding of a limited amount of pure feedstuff after prolonged fasting and followed by fasting , the digestive tract and the digestive proces behaves similar to the "normal" situation, where the animals will consume a mixed ration (almost) ad libitum at their own speed. For that reason we did not accept the TME values of Sibbald and had our own AME system.

You will find those data and an example how we measured that in the attached files.

Article The energy content of full-fat soya beans in meal and pellet...

Dear Gielo

The following link described a method for force feeding for broiler, I hope it is useful for your study.

https://www.researchgate.net/publication/275898964_Force_Feeding_Methodology_and_Equipment_for_Poultry

In another hand, I think that the world's poultry production tend toward avoiding stress on birds and encourage poultry welfare, and the force feeding represents stress procedure on the birds.

Good Luck

Article Force Feeding Methodology and Equipment for Poultry

You could use broiler cockerels at the appropriate age. Cockerels are fasted until their digestive tract is empty, and then fed on a single meal of feedstuff under investigation (McDonald et al., 1987). Excreta are collected until all residues of the single meal have been emptied. At the same time, the small quantities of excreta voided by fasted birds are collected, as a measure of endogenous losses. The energy of the endogenous losses is deducted from the energy of the excreta of the fed birds to estimate true metabolisable energy.

 @Mr. Hassan, unfortunately, there's still no full text of the said document. 

 @Mr. Kan, I am also quite anxious with my study being accepted, as Sibbald's method can induce stress on the subjects, and this could mean bad news for my study in line with animal welfare.

Thanks a lot for the document that you sent to me. So based on the idea, I should just continue applying restricted feeding but only with the investigated feedstuff? And then collect the feces excreted for the last 3 days of my study. Am I on the right path, Mr. Kan? :)

Dear Gielo

I would hesitate to feed only the test feedstuff to young (growing) broilers. In some cases the feedstuff might contain enough nutrients to sustain a more or less normal development, but that is certainly not true for all feedstuffs. For that reason we always fed a mixture with a basal feed to ensure "normal" body function. Thus both the basal diet and the mixture were tested and the difference in results attributed to the test material. This procedure was used in the soybean trial as described in our paper.

A three to four day collection period should be sufficient

Mr. Gielo, I'm glad that I have a "kabayan" who is pursuing this study on broiler feeding.

I'm  also interested on this subject though I have no direct knowledge on poultry farming. However, I have read lots of publication on poultry feeds. KUDOS to us filipinos....MABUHAY!