Agriculture

Feed Withdrawal: A Practical Look at Its Effect on Intestine Emptying, Contamination and Yield

Chickens

Dr. Stan Savage Extension Specialist University of Georgia
October, 1998

Introduction

When broiler companies experience contamination problems at the plant, many will routinely increase the feed withdrawal time. Unfortunately, this may be the exact opposite of what needs to be done. During processing, certain windows of opportunity occur that will decrease the potential for contamination. Knowing when these windows occur requires an understanding of the dynamics of feed withdrawal and its effect on the bird's intestine. A variety of factors influence the eating and drinking patterns of the broiler flock: temperature, ventilation, equipment, and lighting programs are a few. The goal is to recognize and establish a steady-state eating pattern in the flock. Once this goal is reached, the feed withdrawal time can be adjusted as dictated by the season to hit the first optimal window for processing birds with minimal contamination.

This guide explains the effects of feed and water withdrawal on intestinal emptying in broilers. The guide covers steady state consumption and binge eating, and clarifies what happens to feed once it is eaten. Further, it explains the various forms of contamination and details the time required for emptying of the crop, gizzard and intestines. Finally, it relates how feed withdrawal affects yield and provides pictures of broiler intestines after various time periods of feed and water withdrawal.

Phibro Animal Health has supported the reproduction of this guide as a service to poultry producers in Manitoba and to poultry producers worldwide. For additional information, please contact Phibro Animal Health (1-888-403-0074) or visit their website (www.phibroah.com ).

Steady-State Feed Consumption: The Goal

Steady-state feed consumption refers to the eating pattern of a broiler. Broilers in a comfortable environment with full lights or nearly 24 hours of lights and constant access to feed and water consume both feed and water at a steady rate throughout the day and night. Individually, broilers are meal eaters. If broilers have easy access to feed, they will eat about every 4 hours and will drink several times during the 4-hour feeding cycles. A good eating pattern can be verified in a flock by palpating the crops of 50 to 100 birds, which should reveal 30-50% of the broilers with feed in their crops. No birds should have more feed in its crop larger than the size of a golf ball, which is indicative of binge eating.

Binge Eating and Why it Occurs

The normal eating cycle may be affected by many factors in the birds' environment. If birds do not eat for a period, they will try to replace the amount of feed they missed. The longer the period of deprivation, the more excessive the binge. Birds binge usually as a result of one of the following conditions:

  • the lights have been off for a period of time
  • feed has not been available
  • the birds have been trained to eat and drink at irregular times
  • the house temperatures has been so cool or hot that the birds are not comfortable

Light interruptions cause birds to stop eating. When the lights come back on, all the birds that missed their normal feeding want to eat at the same time. Crowding of the feeders and waterers results. The longer the lights were off, the more severe the crowding. If crowding is excessive, birds that are unable to gain access to feed try to climb over birds in front. Cuts and scratches (possibly resulting in type 2 IP) can result. With the pushing and crowding, some birds eat less than they desire and will return to the feeders sooner than 4 hours, causing more crowding. As mentioned earlier, any time broilers miss a normal feeding, they overconsume at the next opportunity in an effort to catch up on the feed they missed. If non-eating periods are repeated, broilers will be trained to eat larger quantities when feed is available. Broilers taught to binge are hard to retrain to normal eating patterns.

Temperature has a great deal to do with binge eating. Lower than desirable house temperatures and/or air movement that reduces the effective house temperature causes the birds to stop eating, and then binge later. Ideally, birds should be comfortable so that they will eat at a steady state 24 hours per day. The ideal house temperature for birds is one at which they are comfortable enough so we can see birds moving at any time of day or night. Ideal bird movement occurs when, at all times, groups of birds can be seen standing and maneuvering their way across the house to the feeders and drinkers. Any time an entire house of birds is sitting and resting on the litter, they are not comfortable. They have rejected the air temperature at a foot high and have opted for the litter temperature which is usually 90°F.

Air movement reduces the effective temperature. The greater the air movement, the warmer the house temperature must be. A broiler's desire to eat is often overridden by temperature only a few degrees too low or by excessive air movement, factors that might seem insignificant to a human.

In excessively hot houses birds will be seen standing and panting, possibly with dropped wings, or sitting on the litter panting. Temperatures that are too low or air speeds that are too high will cause birds to respond by sitting on the litter. When birds sit on the hot litter (generally built-up litter has a temperature of 90°F) their core temperatures increase and they may pant. Birds offered a low air temperature or excessive air movement will drop to the floor and accept the excessive floor temperature. Optimum environmental conditions to achieve the best feed conversions occur when a small percentage (10%) of the flock can be observed standing and panting.

Feed Passage Down the GI Tract

After eating, a broiler drinks some water, solubilizing part of the feed in the crop. This liquid portion passes into the proventriculus (stomach) and on into the gizzard. The feed remaining in the crop dries, and the bird must drink several times to pass all the feed out of the crop. Thus, the feed is metered out of the bird's crop. The gizzard is also a metering device. Liquefied feed entering the top of the gizzard from the crop, via the stomach, is squeezed by contractions, which force the most liquefied portion out of the gizzard into the duodenal loop. This process leaves a rather dry material until more liquid enters. The gizzard mixes the dry material with new liquid and forces out a portion of the mixture.

If broilers cannot or do not eat feed, they will eat litter or drink water. Even though neither of these has any nutrient value, either can force feeding remaining in the gizzard up and out, giving the broiler the nutrients. Naturally, broilers prefer feed but will eat litter or drink water if feed is not available. If a gizzard is opened, its contents will reveal the availability of feed to the broiler on its last day. If feed have been adequately available to the bird, only feed with some water will be found in the crop and gizzard. If any litter is found in the gizzard, either mixed with feed or by itself, the bird was off feed for an excessive period of time.

Contamination and Feed Withdrawal

During processing of broilers, carcasses may be contaminated. The definition of contamination refers to the contents of the digestive tract on or in the carcass. A variety of materials can contaminate the carcass (see chart).

Possible Sources of Contamination

Feed

The bird ate too recently, or they had no access to water. 

Watery Contents

The birds drank excess water long after feed  was removed, or the lining of the intestine which is 90 to 95% water can be breaking down.

Feces

Digested feed that has not been passed prior to evisceration. 

Bile

Bile continues to be manufactured by the liver and accumulates in the gallbladder when feed is not passing. Bile contamination is greater with long-term feed withdrawal when some bile is dumped into the intestine. 

Broken Down Intestinal Lining

A common form of contamination after  the birds are off feed longer than 8   hours. Duodenal lining starts sloughing at 8 hours. Sloughing progresses down the intestine with time. 

Litter

Feed was not available and the birds ate litter which is present in the digestive tract. 

Cecal Contents

Once feed passage stops, cecal dumping  becomes irregular and enlarged cecas result.