Broiler-feed withdrawal

Feed withdrawal is the first stage in the process once the chickens have reached the required live weight for sending to the processing plant. This operation seeks to ensure that the chickens arrive at the plant with their digestive system as clean as possible, so that the process can develop normally.

It is recommended that eight to twelve hours should span between the moment it is decided to send a chicken to the slaughter plant and the actual slaughter. Under normal circumstances, the transit of food through the digestive system takes about eight hours. An adequate feed withdrawal ensures that between 80% and 85% of the intestinal contents have been evacuated during the first six hours prior to processing.

Over the years, there have been many papers published about how feed withdrawal before processing affects broiler yield. Specific findings vary somewhat, but the authors generally agree that the longer a broiler is without feed and water, the greater the yield loss. Off-target withholding not only affects yield, it increases the likelihood of contamination in the processing plant, which may affect compliance with the USDA Food Safety and Inspection Service’s microbiological performance standard.

Research shows an average live shrink — catch weight minus dock weight — of 3.8% at 8 hours.3 Other experts reveal the range to be between 0.18% and 0.43% per hour of feed withholding. Mathematically, live-shrink loss means diminished feed conversion. It’s common broiler-industry practice to withhold feed and water to empty the intestinal tract before birds go to processing. That large body of scientific research I mentioned earlier has shown a direct link between time without feed and the incidence of fecal contamination at the plant, which can increase the load of foodborne pathogens like Salmonella.

Throughout the industry, there are many arbitrary ways used to calculate the feed-withdrawal period. The only correct way, however, is the one that measures the elapsed time from final consumption to slaughter.

The time it takes to catch a house and transport birds from the farm to the processing plant — plus the time in the holding shed once they arrive — need to be factored in. But those activities do not affect the optimal time between the flock’s last meal and the stunning period.

A prerequisite for optimal feed withdrawal is steady feed consumption. Broilers in a comfortable environment with full lighting, or near full lighting, consume feed and water at a steady rate throughout the day and night. They will eat about every 4 hours and drink several times during that 4-hour cycle. Feed outages, light interruptions and cold or hot house temperatures result in binge eating and engorgement, which makes feed-withdrawal optimization almost impossible. Any disturbance in steady-state consumption will affect intestinal-tract emptying and, consequently, sanitary dressing at the processing plant.

A broiler with steady-state feed consumption and full access to water will have an empty crop about 4 hours after feed withdrawal. Birds caught 4 hours after feed removal and processed 3 to 4 hours later will have tight, contracted gizzards containing a small amount of dry feed that’s sometimes mixed with litter.

With steady-state feed consumption, feed leaving the gizzard and entering the duodenum exits the intestine in about 2 hours. If normal intestinal contractions occur, the lower intestine and cloaca will be empty 2 hours after feed has stopped leaving the gizzard. The purpose of feed withdrawal is to allow the contents of the gastrointestinal tract (GIT) to be emptied prior to processing. This reduces the risk of faecal contamination at the processing plant, resulting in better profitability, product safety and shelflife. It also reduces the labor costs associated with re-processing carcasses to remove or clean contamination.

Feed withdrawal plans should be monitored and reviewed constantly and must be modified promptly if problems occur, but as a general rule of thumb, feed should be removed from the flock eight to 12 hours before the expected processing time.