Options for Slowing Down Growth in Pigs

Posted: April 14, 2020 | Written By: Mark Whitney, Ph.D., Form-A-Feed Nutrition and Production Specialist


The current swine market, affected in large part by the COVID-19 crisis, is in a precarious position.  Market prices for producers are already low, but if packing plants end up decreasing or temporarily suspending the processing of pigs, as we have started to see already, we may be facing a situation where pork producers may  need to hold onto pigs for extended periods of time, as shackle space will be at a premium and unable to handle current production levels.  Pigs are not like corn, we can’t simply store them in a bin until market conditions or accessibility improves.  If packer processing drops below the number of pigs needing to go to market, it would be unprecedented, and may require significantly slowing down the growth of pigs in the short term.  What can be done?  The following list is an attempt to identify current options producers may need to consider:

Remove dietary growth-promoting technologies

This is perhaps the easiest method to implement, but one needs to consider unintended consequences.  Not only will ADG be reduced, but often feed conversion and/or carcass yield will also be negatively affected.

Reduce energy density of diets and increase bulk density

Feeding high levels of dietary fiber to decrease overall energy intake can be very effective in reducing growth rate by 5 – 10% or even greater.  Ingredients such as distillers dried grains with solubles (DDGS), wheat midds, soybean hulls, whole oats, or barley, when fed at high levels (achieving 20% or greater NDF in the complete diet) are good candidates, assuming they are available and at a reasonable price.  For example, in many areas, supplies of DDGS have become limited and prices have increased considerably if they can even be bought.  High fiber levels (20% dietary NDF or greater) are necessary to achieve sustained reductions in growth, otherwise pigs will increase their feed intake to achieve similar daily energy intake (within a pigs physical limit, they will adjust intake to meet energy needs).  Other high fiber ingredients, such as straw or alfalfa, can also be very effective in decreasing pig growth, but typically are not feasible due to limitations in handling and processing in modern feed manufacturing systems.

Remove fat from diets

Animal fats and/or oils are used to increase dietary energy density, but if we are wanting to slow down pig growth, decreasing energy intake is a key component.  Remember, pigs will consume more feed (ADFI) with lower energy to a point, so feed conversion will be poorer.  Additionally, other nutrient levels (amino acids, calcium and phosphorus, etc…) should be adjusted based on estimated pig intake.

Decrease amino acid levels in diets

Reducing the lysine:energy ratio, in addition to other amino acid levels, can effectively lower ADG by up to 10% or greater.  Amounts reduced will vary based on the level reduced and timing, but realize that again, negative consequences can be expected, including reduced feed conversion and fatter pig carcasses if done prior to marketing.

Decrease the dietary cation-anion difference (DCAD)

Decreasing the DCAD significantly, through inclusion of feed additives such as calcium chloride or ammonium chloride, has been shown to lower feed intake.  Reductions as high as 30% in ADFI have been observed, but a limited number of trials have evaluated this method.

Changes in production management

A variety of management items can be done in the barn to reduce growth performance.  However, although they can be very effective, they may encourage tail and flank biting and fighting in pigs, so increased management and observation is required.  Restricting feed access by tightening feeder adjustments can decrease feed wastage but also can decrease feed intake, and thus ADG, due to increased competition at the feeder.  A 6-8% reduction in ADG can be achieved dependent on prior feeder management.  Physically restricting feed access can be very effective in reducing growth in pigs, but is also much more difficult to manage, resulting in decreased feed conversion, increased weight variation, and potentially less full value pigs reaching market.  Restricting floor space during the growing and finishing period has been shown to reduce growth rates in excess of 10%, dependent on time and amount of reduction in space allowance.  Finally, increasing the barn temperature by minimizing ventilation rates will increase both the temperature and humidity, and thus increase the effective temperature felt by pigs, potentially reducing growth rates by 10% or more.  However, increased observation and caution must be taken to ensure that ventilation is not reduced to the point that it becomes a health hazard for pigs or people.


Any one or multiple items on this list can be initiated to effectively slow down the growth of pigs, but moderation is key, and negative consequences will occur for all.  Becoming too aggressive in implementing any one or several items can severely impact animal welfare.  It is especially important that producers considering such actions first consult with trained professionals, including their veterinarian and nutritionist, to ensure a proper balance to achieve slower pig growth while minimizing impact to overall animal welfare as well as production costs.  Hopefully such actions are not needed, but it is better to be prepared in case this scenario becomes reality.