Zero Hours of Feed Withdrawal

Feed and digesta are found in the crop, stomach (proventriculus), gizzard and intestine. Because it is full of digesta, the intestine is round and tubular and will remain round as long as it is prepared to accept new feed (up to about four hours after the last meal). Some isolated areas of the intestine will not contain digesta due to the peristaltic muscle movements which move feed through the intestine in "waves." The gut wall is very elastic and curls back on itself when cut open lengthwise. As long as feed is passing through the gut, the ceca dump their contents on a regular basis and will be relatively small compared to later stages of feed withdrawal.

Two Hours of Feed Withdrawal

As long as the birds have had two or three drinks of water, most of the feed in the crop has been solubilized and passed into the stomach and gizzard. The crop is almost completely empty and the duodenum (loop of intestine immediately after the gizzard) is starting to empty.

   
Four Hours of Feed Withdrawal

The crop is empty but the gizzard contains some feed. The gizzard is a "hang down" organ and generally passes out feed only as new feed enters. Since the bird has stopped eating, no new feed is entering the gizzard to push out the remaining feed. The gizzard empties only if the bird drinks excess water or after a long feed withdrawal time. The gall bladder is small but will start to increase in size as feed is no longer passing through the upper half of the intestine. The liver will start to shunt bile to the gall bladder to be stored instead of passing it on to the intestine. Liver colour has not yet changed. For the most part, the intestine still has a rounded, tubular appearance.

Six Hours of Feed Withdrawal

Ideally, the gizzard contains firm, dry material which is comprised mostly of feed. The last feed to enter the gizzard has been squeezed hard by the gizzard muscle, helping to "wring out" most of the moisture in the feed. If the bird drank excess water after emptying the crop, the gizzard will contain watery fluid and the last feed in the gizzard will be in the intestine. Due to reduced peristaltic muscle movement, this material may remain in the intestine for ten hours until the gut lining breaks down and creates sufficient liquid in the gut to help flush out the remaining feed. Until then, this material is often trapped in the last third of the intestine. It is desirable to keep the last feed in the gizzard.
    

The intestines have their maximum breaking strength and will maintain this resistance to breakage for the next six hours. After 12 hours off-feed, intestine breaking strength declines dramatically. The gall bladder is still small but starting to increase in size as the liver begins to shunt bile to it.
    

Eight Hours of Feed Withdrawal

(Start of First Window)

The duodenal loop is enlarged due to the gas production that occurs as the gut lining breaks down and bacteria numbers increase. The rest of the intestinal lining is intact and very little of it will release when lightly scraped with scissors. Cutting open the intestine at mid-gut (at Meckel's diverticulum or the yolk stalk remnant) will reveal villi in good condition. If a finger is placed under the intestine and scissors are used to scrape the exposed villi on that section of intestine, a rough surface similar to a cat's tongue can be felt. The intestine is almost completely empty of feed and most of the intestine is flat. Small amounts of gas are present in the intestine.
      

Twelve Hours of Feed Withdrawal

(End of First Window)

Most of the intestine (beyond the duodenum) is flattened. Flattened intestines are less likely to be nicked, cut or torn when the body cavity opener and vent cutter cut into the carcass as it hangs on the processing line. The villi are not as easy to feel when performing the "cat's tongue" scratch test and the intestine does not readily curl back on itself when cut lengthwise. From this point on, a steady decline in intestinal breaking strength occurs.

Thirteen Hours of Feed Withdrawal

Enough broken down intestinal lining has accumulated in the duodenum to trigger the gall bladder to release bile. Reverse peristalsis, the backward movement of material which regularly occurs in chicken digestive tracts, carries the bile from the intestine into the gizzard. Some of this bile may then run back into the crop during processing. Green bile staining of the gizzard is a good indicator that a bird has been off feed for 13 hours or longer. Some gall bladders now start to appear smaller as they dump their bile contents.
    

Fifteen to Seventeen Hours of Feed Withdrawal

The intestine is almost entirely rounded as it fills with gas and gas may bubble out if the intestine is nicked. The entire gut lining is broken down and sloughed lining is found in much of the intestine. Almost nothing is felt when performing the "cat's tongue" scratch test to detect villi. Due to dehydration, the crop tends to stick to the carcass and is difficult to pull out; crops and sometimes stomachs will break as the viscera are removed from the carcass. The gizzards are becoming more difficult to peel.

   
Eighteen Hours of Feed Withdrawal

(Start of Second Window)

The broken down intestinal lining has passed out of the bird and the intestinal villi are starting to rebuild. The villi can be detected with the "cat's tongue" scratch test and little material scrapes off when scissors are run over the exposed intestinal lining. The intestine is now flattened again and little gas production is visible. The intestine has lost about one-third of its breaking strength during the past six hours and the crops are still difficult to remove due to dehydration. Contamination is lower than "between the windows" because the intestines are now empty and relatively dry instead of being filled with gas and sloughed intestinal lining. If the bird does not receive feed in the next several hours, the intestine will start to slough again.

A Guide to Judging Time of Withdrawal After First Window Has Passed

Signs Feed Withdrawal Has Extended Beyond First Window (13+ Hours)

• Crops and stomachs break more easily during processing.
• Gizzards and sometimes crops are stained green with bile.
• Some gizzards are completely empty.
• Gizzards are tougher to peel.
• More gizzards contain feathers, litter or feces.
• Denatured protein ("cottage cheese") is found in some gizzards.
• Some gall bladders (those that have not dumped their contents) are greatly enlarged.
• Bile, urates or orange casts (sloughed lining) are seen in the truck crates or floor.

Signs Feed Withdrawal Has Reached Second Window

• Smaller, shorter duodenum.
• Flattened intestine.
• Little sloughing or gas in intestine.
• Can feel villi during "cat's tongue" scratch test.
• Some or all of signs of extended withdrawal listed above.

Do Not Be Fooled by False Signs

• Reverse peristalsis can bring previously sloughed material back into the duodenum. If the villi are rejuvenated, the sloughed material in the duodenum is old.
• Feed found in the crop could be due to water run back from the gizzard. Suspect this problem if the gizzard is empty.
• Excess water consumption can flush bile out of the gizzard. Bile staining may not be observed in every bird after 13 hours of withdrawal. Watch for excess fluid.

Carlyle Bennett
Animal Industry Branch, Manitoba Agriculture and Food
August, 2002