Slowing broiler growth under special circumstances using feed/nutritional interventions

Shivi Rao, senior nutritionist at Cobb-Vantress reports on slowing broiler growth.

Young white hen looking at the camera with a group of other chicken behind it in a poultry farm bred especially for meat and eggs
Young white hen looking at the camera with a group of other chicken behind it in a poultry farm bred especially for meat and eggs
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According to the National Chicken Council, the United States poultry industry processed over 9.22 billion broilers in 2020. To accomplish this feat, the poultry industry relies on a vertically integrated production system (Figure 1) to secure the seamless flow of poultry products from the breeder farm, through the hatchery, to the broiler farm, and to the processing plant. The logistics for each step are tightly coordinated so that when product is moved from one link in the supply chain, the next link is ready to receive the product. This not only secures the welfare of each bird, but it also improves the efficiency of a system that operates on razor-thin margins. Problems arise when disruptions in the supply chain occur. Quick action and decisive decisions from a competent team will solve supply chain disruptions, but the solution will often require scheduling changes. This article will focus on how to respond to disruptions that delay flocks leaving the farm and entering the processing plant.   

Modern commercial broilers are fast growing, averaging 60 grams (2.1 ounces) per day over the course of the production period with maximal growth occurring 3 weeks post-placement. For this reason, the entire broiler production process is characterized as “just in time” with harvesting and delivering broilers to processing plants scheduled precisely to maximize efficiency. However, occasionally, we receive requests for nutritional and feeding interventions to slow down broiler growth. Most recently, the supply chain disruptions caused by the COVID-19 pandemic has created conditions necessary to manage broiler body weight. Other reasons for supply chain disruption stem from labor shortages (for harvest and/or processing), sudden change in demand (pandemic, unexpected trade restrictions, or disease), or natural disasters (ice storms, flooding, fire, or power outages).  

The degree or magnitude of broiler growth slowdown is driven by the severity of the disruption keeping the birds from moving off the farm to the processing plant. The actions needed to slow broiler growth by 1 or 2 days varies greatly from those needing to slow growth by as much as 6 or even 10 days. The primary goal, when applying a growth intervention strategy, is to slow growth and maintain carcass quality without adversely affecting bird health and elevating mortality. However, these interventions may have an impact on carcass and breast meat yield.  Successfully slowing broiler growth depends on the following general nutritional recommendations:

  • Lower the percentage of dietary digestible lysine (%dLys) and dietary energy.
  • Formulate all other essential amino acids in an ideal ratio to %dLys.  
  • Ensure that amino acid levels go down proportionately when %dLys is lowered.
  • Do not to use any minimum limit on percentage protein in the feed formulation software.

Specific dietary recommendations for slowing broiler growth and achieving the desired market weight are provided. Management must always meet the basic needs of the flock while adjusting the program to benefit fully from the breeds’ potential. Some of the guidelines may need to be adapted locally according to your own experience or infrastructure and to allow you to comply with any national requirements for animal welfare or animal care. Work with Cobb’s local technical service and world technical support teams when managing a flock experiencing a processing delay.   

Cobb Road Map

A diagram of the supply chain and production continuum for broiler chickens. 

Slowing broiler growth by 2 to 3 days

Small broilers (processing weight < 1.75 kilograms, 28-to-30-day grow-out): Successful intervention should start about 7 to 8 days prior to the normal market age. If three diets are used in the grow-out program, then we recommend lowering the energy content of the last feed by 200 to 250 Kcal/kg (90 to 115 kcal/lb) and %dLys content by about 0.05% units. For example, lowering 1.15% dLys to 1.10% dLys. Begin feeding this modified diet 7 to 8 days prior to the original market age. Manage feeding time after 3 weeks of age by practicing feed restriction for 2 to 3 hours per day. Apply the feed restriction at the same time every day. Reducing light intensity in the broiler house (if possible) should increase the intervention efficacy. Feeding a pelleted diet with a high percentage of fines will also slow feed consumption rates.    

Medium and large broilers (processing weight > 1.75 kilograms): The procedure for managing medium and large broilers is similar to that for small broilers with interventions beginning at 7 to 8 days prior to the normal market age. First, lower feed energy content by 150 to 200 kcal/kg (as compared to the normal feed) during this period. Reduce the %dLys by 0.07% units (slightly higher than the small broiler program). Also, consider feeding mash or a pelleted diet with a high percentage of fines to slow the rate of feeding. If feed restriction is necessary, then begin a short 2-hour restriction at a younger age (12 to 14 days of age). This will allow the young birds to adapt to daily short-duration restriction. Delaying feed restriction to older ages may lead to heavy competition at the feeder, resulting in skin scratches and bruising. Another option is to increase the dark period to a legal maximum. A cocci vaccination program is more suitable than a coccidiostat program for cocci control if feed restriction is planned.

Slowing broiler growth by 4 to 6 days

Small broilers (processing weight < 1.75 kilograms, 28-to-30-day grow-out): This would be difficult to achieve. The intervention should be started around 12 days of age. It is not recommended to make any changes to the starter feed, but a diluted second feed should be introduced at 12 or 13 days of age. The feed calories and %dLys in the second and third feed should be lowered by about 200 to 250 Kcal/kg along with lowering %dLys by about 0.05% units as compared to the normal feeds. If further action is needed, follow the recommendations for a small broiler in the previous section regarding feed restriction, light reduction, and pellet quality. 

Medium and large broilers (processing weight > 1.75 kilograms): This procedure is like the small broilers recommendations with interventions beginning 12 to 13 days of age. The second, third, and fourth feed (if necessary) all must be reformulated with 200 Kcal/kg of lower energy than the normal feeds and reduce %dLys by about 0.07 % units. Also, providing a pelleted feed with a high percentage of fines or even mash feed will slow consumption rates. If necessary, slight feed restriction could be applied but this needs to start at 12 to 13 days of age. Allowing the broilers time to adjust to the short 2-to-3-hour feed restriction period will minimize scratches resulting from crowding at the feeder.

Slowing broiler growth by 7 to 10 days

Small broilers (processing weight < 1.75 kilograms, 28-to-30-day grow-out): This slowdown may not be possible in a small broiler program.

Medium and large broilers (processing weight > 1.75 kilograms): This is a significant intervention that may include feed restriction and feeding a different starter feed. Broiler chicks should be started with a starter feed like the one used for replacement pullets (18 % protein, 0.95 % %dLys, 2740 Kcal/kg). Feed pullet chick starter up to 21 days of age and start feed restriction at around 14 days of age by providing about 80 % of the daily ad libitum feed consumption shown in the Cobb technical supplement ( When exact feed measurement is not possible, consider other methods of restricting feed intake including extending dark hours, raising feeders, or other methods of limiting feed access. The goal is to initiate feed restriction at a young age.  This will allow the flock time to acclimate to the change. At around 21 days of age, begin feeding a pullet grower feed (as in replacement pullets). If possible, restricted feeding should be continued by limiting the feed quantity to about 60 % of the daily feed consumption shown in the Cobb technical supplement. Allow the feeding of pelleted feed with a high percentage of fines or, better yet, switch to mash feed after 21 days of age. The pullet chick starter and pullet grower feeds suggested here contain 15 to 25 % of bulk or “filler” ingredients like wheat middlings, rice mill feed, and soy hulls. It is important to realize that quickly increasing the supply of dietary filler ingredients could create an issue with feed storage space. The logistics of the filler ingredient (raw material procurement and storage at the feed mill) needs to be planned and coordinated. To successfully implement this broiler slow-down program, secure a continuous supply of diluted feeds for the restriction period. An additional option to consider, if possible, is replacing the complete feed with 30 to 40 % of whole wheat or cracked corn (maize) at the farm level. This could also be used to slow growth. If substituting whole wheat or cracked corn, care should be taken to ensure that at least 50 to 60 % of the feed provided contains vitamin premix and mineral premix. Inclusion of whole wheat or cracked corn beyond 40 % can lead to dietary deficiencies. 

The vertically integrated poultry industry allows management of all aspects of the production process to not only control costs of production but to also use space more efficiently, purchase in volume, and maintain better quality control over product. Having all the production segments under one umbrella also allows rapid adjustments across the supply chain if issues appear. Fortunately, rapidly growing broilers can be slowed and managed to market weight by adjusting dietary composition, feed form, and minor restriction practice. The key is to recognize the supply chain disruption and recalibrate the processing date so there is time to make the appropriate adjustments to slow growth to meet the new processing date.      

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