Chemical burns in gizzard caused by formaldehyde
The use of formaldehide as a salmonellicide in balanced feed is restringed in most countries and allowed in some others.
This substance reacts, when arriving in the gizzard, with the hydrochloric acid secreted in the proventriculus and two substances are originated: formic acid and bis chlorometil ester. This last substance has a well known cancerogenic effect, after its absorption in the intestine.
However the production of high quantities of formic acid, locally in esophagus entrance, causes burns in the corn layer of the gizzard as it can be noticed in photo 1/3 of this blog.
To distinguish this injury from fungic injuries or mycotoxin burns, we must take a look at:
(1) the lower layer of the corn layer must be free of fungic growth (photo 2/3). This may appear as a white spot due to fungic filaments growth.
(2) duodenum must appear with normal colour and consistence (photo 3/3). In case of tricotecenes burns, duodenum would appear with a reddy image due to burns in microvilli.