How many hens are there in the production unit , and what is the daily laying percentage? Is the flock a local breed or a commercial hybrid?

What characteristics are you going to measure, what is their variability and what differences do you want to show to be significant.

For egg shell measurements room temperature is generally OK, for internal characteristics storage at 4C is advised if the storage is longer than several hours.

So many questions before a clear answer can be given.

Consult also the information on this topic from the extension services of several US Universities or commercial breeders.

Dear C.A. (Kees) Kan Thank you very much for your quick reply and reactivity,

First of all, I'm in the census procedure of the production units, so far the units I'm planning to visit have a hens number varying between 90.000 and 120.000.

So far I don't know about the daily laying percentage, for this particular purpose I'm preparing a survey to be filled by the producers.

The main motivation behind my question is the fact that I wanted to visit the production units as minimum times as possible due to the sanitary conditions.

The characteristics I'm interested in are mainly toxicological.

Hope I cleared your questions in the correct way.

Warmest regards.

I do not understand what toxicological characteristics you think to find in eggs. Having done experiments on laying hens with organochlorine pesticides, dioxins, mycotoxins, feed additives and veterinary drugs during about three decades, I have a hard time to imagine what things you hope to find, unless I missed some very important developments during the last years that I was retired.

I attach a rather recent paper which tackles the residue issues in eggs.

Dear C.A. (Kees) Kan thanks for your reply,

I'm mainly looking for mycotoxins in eggs produced in my country (i.e Algeria) this is mainly motivated by the fact that eggs are the main source of proteins among Algerians people and they (eggs) are highly consumed in my country.

Unfortunately, no research has been done in my country regarding mycotoxins.

With this in background, I kindly ask you to clear my questions about the sampling procedure, I'm in my first year of Ph.D. and I'm just starting my research.

Warmest regards.

PS: thank you for sharing your research paper with me.

Dear Chahinez Laouni

You have taken on quite a job!

First: Mycotoxins will enter the laying hens exclusively via the feed. Any levels to be found in eggs are, due to the physiology of egg formation a reflection of the intake during the last 14 days (or even more).

Second: the large poultry farms certainly get their (new) feed from commercial feed mills every week or 10 days (or even more often). Given the size of your country these mills will be located relatively nearby.

Third: You need a quite sensitive and specific analytical method to assess the amounts of mycotoxins and possibly some of their (toxic) metabolites, as levels in products of animal origin are usually quite low. Remember that plants and plant material are the primary source of mycotoxins and the passage of the mycotoxins through the animal will considerably reduce these levels by metabolism.

Fourth: Any mycotoxins in eggs will be rather evenly spread amongst the hens, so 10-30 eggs from one farm at one time seems adequate to me. These eggs might be contained for up to a week or so on room temperature. For longer storage break the eggs and store the mixed whole egg at -20. I would advise to take samples during at least one year at each farm, to account for seasonal variations in the feed ingredient contamination with mycotoxins.

Sampling of feed mills might be a first step to know which mycotoxins are most likely to be found.

At the end, the contribution of animal food products to the mycotoxin burden of the population might be small compared to the one from plant derived food products.

Good Luck

Dear C.A. (Kees) Kan thank you very much for your clarifications, you enlightened me about how to start my research journey.

Thank you again sir, and if you don't mind I will keep you updated about my work progress through inbox messages.

Warmest and deepest regards.

All the best. Looking forward hearing from you.

As a gimmick a copy of a lecture I - being a young ambitious scientist - gave 40 years ago about mycotoxins and future research goals in poultry. You can read from this, that a lot has been accomplished in those four decades. But still a lot has still to been done.