Maximizing Yield Key to Higher Returns

Procedures to increase product yield, regardless of product mix or accounting procedures, are outlined by David Beaver, Technical Processing Specialist with Cobb-Vantress, Inc. in the company's latest 'Technical Focus'.
calendar icon 21 August 2012
clock icon 19 minute read

In all processing plants, the most important driver for reducing cost is yield. Maximizing yield and yield value is the difference between average and outstanding returns, and in some cases making a profit or losing money.

Product costs are driven by dollars and volume. Increased yield will drive down the costs of salable product and increase volume without additional costs for raw material, labour or overheads. Therefore, from a plant standpoint, yield is the most important number that affects the bottom line.

Understanding and evaluating yield in today's operations can be complex due to the many product mixes sold around the globe, as well as accounting procedures, which could be completely different from one company to another. If done properly, the procedures outlined here will increase product yield regardless of product mix or accounting procedures.

Poultry plants today span a wide range of automation levels. This is driven by many factors such as labour cost, customer demand, product mix sophistication and the financial ability to purchase technology. Regardless of the level of automation and product mix, there are three basic process steps common to all operations. The understanding and execution of these steps is critical to maximizing yield, and in turn the operation's profitability.

It is important to remember that a great plant yield will always start with a good live product from the farm. All the activities - from breed selection, hatchery, brooding, live programs and farm management – combine to produce the quality, uniformity and yield aspects of the bird. Most of the costs of the salable product are already in the birds at this point. The plant's responsibility is to convert the potential of the live bird into high quality products at the lowest possible cost.

Keys to maximum yield
  • Start with a good product
  • Good nutrition
  • Good live programs
  • Farm management
  • Good plant management/operations
Key: Good genetics will not overcome poor farm management or programmes

Holding area loss prevention
  • Minimize holding time through good logistics and communication
  • Good holding area design that minimizes stress and promotes bird welfare
  • Fans and water atomizers
  • Measurement of results

Yield is the major component that drives the level of success of this conversion. Presented here are the first three areas of a plant operation and some critical things that can impact that conversion.

Holding Area

Need to avoid thermal stress

Minimizing holding times and providing proper holding areas for live birds waiting to be slaughtered are necessary to reduce thermal stress and provide proper bird welfare. This is absolutely critical to reduce live shrink and Dead On Arrival (DOA) - the two factors normally used to measure our performance in the holding area.

Holding times should be part of a comprehensive plan that considers feed and water withdrawal, catch and transport times as well as the plant operation schedule. The best results are those that have the shortest holding time at the plant. A good program that maximizes results usually has a goal of holding times of two hours or less at the plant.

Trials in the UK have shown that 40 per cent of all DOA are from thermal stress. This includes the time during transport as well as holding period at the plant. This number should be 0.25 per cent or less.

Live shrink is the amount of body weight that live birds will lose from the time they arrive at the plant until they are processed. This shrink process not only is a loss of yield but, if excessive, will cause problems in picking (feather plucking) as the feathers will be harder to remove.

"Holding times should be part of a comprehensive plan....the best results are those that have the shortest holding time at the plant."

Extreme stress at this stage can also cause discoloration of the breast meat, making it appear dark or reddish in colour. In many companies, the live shrink number is measured on every load. In some situations this is not practical but trial measurements should be run on individual loads to establish benchmark values.

These trials should take place over a period of time that will allow the processing facility to establish a correlation between holding time, temperature and the amount of loss. This number will be a good management tool to help develop an effective programme in each situation. In an operation with proper feed and water withdrawal, logistics and good holding conditions, the shrink loss should be less than 0.5 per cent.

The majority of the poultry processing industry uses two main types of holding concepts:

The lairage type holding areas (seen below), typical of some European operations, are very effective, maintaining a controlled temperature and good ventilation. They also provide the opportunity to restrict light which helps to keep the birds calm. This is especially important in countries that require a minimum holding time.

European type lairage, utilizing blue light to help keep the birds calm.

The holding shed concept as pictured), the most widely used around the world, can also provide excellent results. A well-designed shed has high-speed fans located to blow through the coops or cages to remove heat as well as provide a wind chill cooling effect to the birds. These fans should be turned on anytime the temperature reaches 21°C (70°F).

The shed will also need a water atomizer system for use when temperatures reach 27°C (80°F). This will further reduce the temperature in the shed and keep the birds more comfortable. The spray nozzles should be of the type that would emit a fog instead of a spray.

Another invaluable way to measure performance in this area in real time is a visual inspection of the birds being held. If the birds are listless and there is a lot of open-mouth breathing or panting, this is a result, in most cases, of thermal stress and is an indication that there are problems with the holding conditions. This visual observation needs to be made as part of the area supervisor's normal routine and is critical in hotter weather.

Remember the goal of this area is to keep the birds comfortable. This is the proper thing to do from a bird welfare standpoint and will reduce shrink and DOA, resulting in higher yield.

Hanging Area

Consistent supply of birds critical

The unloading and hanging operation sets the stage for the rest of the plant operations. Not only does it dictate the efficiency of the kill operation but if not done properly, it will cause problems and yield loss throughout the operation.

No matter what unloading system is used, it is critical to have a consistent supply of birds to the hanging area to keep the line full. Empty shackles disrupt the stunning process and will cause more birds to float through the scalder resulting in poor picking. Birds that are hung next to an empty shackle will have a greater chance of riding over the top of the picker discs, causing poor feather removal and damage to the bird. If the empty shackle on the kill line results in empty shackles in the evisceration line, it will be more difficult to set the feed timing on all the automated equipment and this will increase the number of misfeeds.

Breast rub

If using a coop system, care must be taken to load the conveyor without dropping or throwing the coops which causes bruising. With the cage and dumping systems, the transition points and belt timing are important aspects to monitor. The belts should be set at speeds to keep a steady supply of birds without dumping birds on top of each other and also to prevent birds from piling up and smothering at the end of the hanging belt.

The hanging pen area must be designed to help the hangers do a good job. A proper hanging area has black- or blue-coloured (not UV) lights and is a darkened area to keep the birds calm. The shackles must be at the right height and distance in relation to the belt and hangers. This will help prevent improper hanging and one-leg hanging of birds which will result in a disjointed bloody thigh as well as causing stun, kill, and picker damage to the bird as it drags through the machinery by one leg.

It is also very important to have the right gauge (gap) of the shackle loops that best match the bird size you are running to prevent damage to the feet. A plant has to check and repair shackle gap as it is normal to have some become bent over time.

A gap bent too open will allow the foot to come out in the feather picking machinery causing one leg disjoints, or possibly pulling the whole bird out of the shackle and into the drain. A gap too tight will result in the hanger pulling down harder and breaking the foot or not being able to get the foot all the way down causing missed stun, kill and pick issues.

Hanging area
  • Lighting conditions
  • Dust removal
  • Proper shackle height and gauge
  • Proper breast rub
  • Proper belt loading
  • Correct bird handling

A breast rub, shown above, is also essential in the hanging area to prevent the birds from climbing the back of the shackles and flapping their wings causing bruises and red wings. Another breast rub should start at the end of the hanging area and continue all the way to the stunner to keep the birds calm and prevent shackle climbing and wing-flapping. These breast rubs are usually made by the plant and can be constructed of scrap sheet metal, guide bar material, old belt material or metal tubing.

Improper hanging grip

Proper hanging grip

Common hanger related bruises - drumsticks

Common hanger related bruises - one leg hanging – leg and drum

Another very important aspect is training the personnel who hang the birds. This must include the proper way to hold and handle the birds, as shown. Proper technique will help prevent drum bruises, and disjointed thighs from one leg hanging.

Also, by handling the birds incorrectly, the hands are below the shackle and must pull down on the drumstick portion of the leg at a 180-degree angle. This will not only result in drum bruises but will also make hanging harder from the friction of the foot coming down the shackle as well as contributing to red discolouration on the paws.

With the correct hanging method, the hands are presenting the birds' legs at a 90-degree angle to the shackle, which gives added leverage. The shank will come down into the gap without the foot dragging down the shackle. This method is much better from an animal welfare standpoint, reduces yield loss and requires less effort from the hangers.

Killing and Bleeding

Challenge to avoid downgrades

The kill-and-bleed step in some form is common to all operations. It is one of the biggest areas of product loss and downgrade in all plants if not done properly.

Regardless of method - or government or religious requirements for the operation - the aim is to slaughter the bird in a humane manner and remove the blood from the carcass. Doing this without damage or downgrade to the bird is the challenge.

In plants that slaughter by hand without stunning, the training of the people doing the cut is critical. The knife must be extremely sharp and the cut, whether halal or side cut, must be done with skill and precision so the bird does not know it has been cut and will lose consciousness prior to death struggle.

Even with a perfect cut, there will be some wing and shoulder damage from the death struggle in all operations using this method. Some companies have been allowed to use a post stunner after the cut step to prevent death struggle. This is a great option to explore with government or religious officials in this situation.

Due to the cost of ownership, operation and flexibility, the most common kill process worldwide is the system using electrical stunning and an automatic kill machine. The electrical stunning has been the source of much debate from the animal welfare standpoint. Most groups in the United States and around the world believe that it is the most humane way and the most effective system that prepares the bird for automated slaughter.

When using the electrical stunner process there are two schools of thought.

The US model, based on industry experience and validated by research of many highly respected groups, is the traditional method used in most plants around the world. This model uses voltage and frequency to produce 20 to 40 milliamps per bird. This has proven to be animal welfare-friendly and does minimal damage and downgrade to the birds when operated properly.

The second model, based on research of other respected groups, is adopted by European Union regulations. This model uses a non-recoverable stun approach to ensure animal welfare guidelines. The regulations set threshold limits for voltage and frequency of current which requires a much higher milliamp per bird (100 at present) than what is used in the US and elsewhere in the world. This system, like the US model, is very effective from an animal welfare standpoint. However, the increase in voltage has also increased the amount of damage done to the bird.

The difference in stunner settings in the two models translates into a huge variance in product damage. This will provide a different perspective on the ways the two groups look at a new technology alternative. However, the animal welfare aspects of both systems are deemed acceptable.

Regardless of requirements to be met, there are common mistakes made in plants and correcting these will help minimize bird damage. These few things, if done properly, will result in a more consistent stun and allow the processor to 'fine tune' the system and reduce some of the stunner damage such as seen in pictures below.

Stunner damage to tenders, breasts and wings

The stunner should be set so only the head and part of the neck is in the water. This will prevent much of the wing damage and discoloration that could be caused by the stunner.

The water management of the stunner is also critical. The most common mistake in stunners is applying too much water with solid streams of water running to the floor. Not only is this a huge waste of water but the floor will act as a ground, which disrupts the current.

Water running out of the entrance of the stunner will also cause pre-shock, which makes the birds jump up, resulting in flapping and wing damage and possibly completely missing the stun effect. Added water should be just enough to replace the water being dragged out by the birds. Many plants are using water sprays on the shackle and foot when the birds enter the stunner as part of the make-up. This not only replaces part of the lost water but helps the ground effect of the stun.

Another effective method to maximize the electrical stun system and make it more consistent is using salt to increase the conductivity of the water. Most systems come with a place to add salt, but this is seldom used. When the stunner is operated with salt at a one per cent solution, the stun becomes more consistent and this allows the operator to fine-tune the settings.

Another area that needs checking in the electrical system is the ground bars. It is extremely effective to have a ground bar on both sides of the shackle to prevent the circuit from being broken when the bird jumps and pulls the shackle away from the ground bar. When the circuit is broken and then reestablished, it has the same effect of the birds being double stunned.

Controlled Atmosphere Stunning

Pros and cons

The other stunning option that is available is Controlled Atmosphere Stunning (CAS). This includes both the chemical types that replace oxygen using CO2 or other gases, or systems that remove the oxygen from the birds by mechanical means. These systems all do a non-recoverable stun.

The CAS systems have some big advantages. They achieve a uniform stun of all birds in a flock, regardless of size. The system provides a much better environment and ergonomic work situation for the live hangers. The birds are non-recoverable, eliminating any chance of a bird going into the scalder alive if the killer misses it. The systems that stun prior to dump also eliminate the bird welfare issues of live birds being dumped and hung upside down while awake.

The CAS systems also have some big disadvantages. DOA identification becomes very difficult. Automatic killing machine settings are more difficult as the wings are not tucked and neck extended. Expect an increase in wings cut by machines in these systems.

Also, compared to electrical stun, the CAS system is much more expensive to buy and operate and does not have the flexibility for line changes. With the chemical systems there will be increased handling and transport safety concerns to consider as well as gas availability.

The other issue apparent with any type of stunning is the amount of broken wings. This will have to be addressed, not only from a product loss standpoint but also the perception of the animal welfare.

After the birds are stunned, the type of kill cut should dictate the bleed time. Not enough bleed time will result in birds possibly entering the scalder alive, excess blood left in the product and reddish colour skin. Too much bleed time will result in feathers being more difficult to remove and yield loss.

Some countries set a minimum for bleed time and these government requirements supersede any other factor. If there is no government requirement, a good rule of thumb is that a cut that severs both carotid arteries and both jugular veins, as well as the windpipe, will bleed out in 90 seconds. A cut to the side of the neck or back of the head severing only one vein and one artery will require 120 to 150 seconds to bleed out properly.

The visual confirmation of your bleed time is at the entrance of the scalder. Before entering the scalder the birds should have their wings and neck relaxed and there should be no bird movement. If this is not the case, the bleed time is too short. If these bird conditions exist much earlier in the blood tunnel before the birds reach the scalder, the bleed time is too long causing picking issues and yield loss.

Scald and Pick

By far greatest potential for yield loss

Over-scald to the breast

Heat damage within breast muscle

Proper scald

Proper chill

The next area common to all operations is scalding and picking - the place with by far the greatest potential for yield loss. This is truly an area where success or failure is measured by small increments and with exacting detail. A half degree of scald temperature can mean a huge loss or gain in yield.

Adjustment of the pickers at every flock change has to be done properly to allow correct picker set-up that will not break wings and mutilate birds or leave too many feathers. All too often, there are instances where the scalder temperature is the quick fix and is used to compensate for poor picking adjustment and picker upkeep.

Regardless of the type of system in use, the upkeep is critical.

The scalder must maintain good agitation to wet the feathers completely. There must be enough picking power and the proper picking finger selection for the current product mix. There must also be a good preventative maintenance and effective finger replacement programme to pick in a manner that will maximize the product yield.

Another key fact in a scald/pick operation that maximizes yield is that 100 per cent of the feathers will not be removed by the equipment. If the scalder temperature is set too hot to ensure 100 per cent feather removal, it will result in over scald of the breast. The tissue and collagen layers underneath the skin are also destroyed. Not only is the weight of the tissue and collagen lost, but this is also what binds the majority of the retainable moisture picked up in the chill process.

The pickers cannot be adjusted to pick 100 per cent of the feathers, but must be set to the largest birds in the flock being run. If set to the smallest or medium birds, the largest birds will be damaged because the pickers are too tight. Because of this, a small percentage of the birds will have a feather or two left on them. These feathers must be removed manually by people downstream in the process.

It is also important to remember that all scalder and picker systems are not the same. Systems should be selected based on the processing plant's product requirements. To minimize yield loss and to scald and pick to the customer expectations, there needs to be a system which balances the scalder with the number and type of pickers designed for each particular product mix.

In plants that are producing a soft scald, retaining cuticle on the product is more successful with longer scalder dwell times - up to three minutes at lower scald temperatures. The best systems utilize three-stage, multi-pass scalders. The temperatures are usually between 49°C and 53°C. This system also needs more pickers on line to target specific areas of the bird. They will often use hock and straddle pickers. In some cases it is also necessary to use a hock steamer to remove the yellow from the hock.

Plants that are producing white, cuticle-off birds will usually use two or three-stage, multi-pass scalders and have less dwell time. They will trade dwell time for temperature as they must scald around 51°C to 55°C to denature the cuticle for removal in the pickers. Dwell time in this type system needs to be 120 seconds.

There are still a lot of single-stage, multi-pass systems in use and many are doing a good job. A lot of these are running shorter dwell times - as low as 90 seconds and temperatures up to 56°C to break down the cuticle. This type of system must be constantly monitored and is very sensitive to line speed changes or agitation problems. It is operating right on the limit of short dwell time and higher scalder temperature. With this type system small changes can translate into big problems . There is no upward temperature flexibility and any temperature increases at all could cause major yield loss.

There are many systems that run single-stage very short dwell times and compensate with higher temperatures. Without exception, all of these plants experience major yield loss from over scalding the breast and destroying the tissue and collagen layers underneath the skin. Any system with a dwell time of less than 90 seconds or a temperature in the scalder above 56°C should be avoided.

With dwell times above 90 seconds, temperatures should be 55°C and below for white birds and 53°C and below for yellow birds. Remember - heat is the enemy of yield. Always scald with as low an effective temperature as possible to meet expectations of your customer.

The chart from Meyn is a great visual to gauge equipment performance. The white over-cooked areas of the breast indicate yield loss. The scalder operation should be run to reduce this as much as possible.

The three areas examined here are only the foundation steps. Not only must they be done properly but all subsequent steps have to be performed properly to maximize yield.

Always remember the goals of our activities
  • Good genetics
  • Good stress management at all live stages
  • Good feed withdrawal
  • Good stun-kill
  • Good scald and picking
  • Proper chilling
= $$$$$ from improved shelf life and retainable yield

August 2012
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