Specially for
@micstrachan - I have done this as a reply to my original post so the sources and my summary stay together.
A few caveats:
- I am not a vet or a poultry nutritional scientist. I do have some experience in reading scientific papers but it is all a long time ago!
- I did not pay for access to full tex t if it was not available for free (I also didn't sign up for anything in order to get access to full text). This means that in some cases I could not judge the scientific methods because only the abstracts were shared. This is important because not all methods are robust and many studies are based on quite small numbers of observations
- In reading any scientific paper on chicken health you need to look carefully at the end point measurements in terms of what they consider a good outcome. Many articles are aimed at the commercial chicken industry and so measure outcomes related to that - such as carcas weight or increased laying. Obviously I was not interested in that so I rejected a load of articles (mainly not included here) whose measurements I could not connect to health in the way we mean it for our beloved chickens
With all that said, here is some reading for anyone who wants to go down the same rabbit-hole that I did!
https://www.merckvetmanual.com/poultry/fatty-liver-hemorrhagic-syndrome/fatty-liver-hemorrhagic-syndrome-in-poultry?query=fatty liver in chickens
https://www.sciencedirect.com/science/article/pii/S0032579119319856
https://pubmed.ncbi.nlm.nih.gov/8378221/
https://www.dopharma.com/technical-support/fatty-liver-haemorrhagic-syndrome/ (this one is from a company selling choline supplements but it is a well written summary of FLHS and cites multiple academic sources)
http://www.poultrydvm.com/condition/choline-deficiency (not really an academic source)
https://cdnsciencepub.com/doi/pdf/10.4141/A06-043
https://journals.sagepub.com/doi/pdf/10.1177/0300985813503569 (this is the California study - it is based on necropsies sent into the state system over a number of years)
https://www.tandfonline.com/doi/pdf/10.1080/03079457608418164?src=getftr (this is not a scientific paper but a published review - old but very helpful - it explains why higher fat and lower carbohydrate in the diet may be best for the chickens because the disease seems to be caused in part by pathology in the manufacture of lipids from carbohydrates in the liver - this is referrred to in the Merck Veterinary Manual and is what
@bgmathteach spotted - higher dietary fat reduces the liver manufacturing fat)
https://www.sciencedirect.com/science/article/pii/S0032579119458914 (support for a diet with 4% fat)
https://www.sciencedirect.com/science/article/pii/S0032579119473720
https://pubmed.ncbi.nlm.nih.gov/31565961/
https://pubmed.ncbi.nlm.nih.gov/12828209/
https://pubmed.ncbi.nlm.nih.gov/27143762/
https://poultry.extension.org/artic...ients-for-poultry/flax-seed-in-poultry-diets/ (this is the article that had me thinking long term use of flax seed increased FLHS - it does not cite any sources for the assertion and I have found no academic study to support it - most say flax is beneficial in reducing FLHS and some say it doesn't have any effect - shame on the USDA, university extension organization and the author!)
PHEW - that was a marathon.
And here is a small tax contribution for Bob as I may now have provided the longest post on this thread ever with no pictures!
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