Tuesday, February 21, 2012

Are extruded feeds easier for a horse to digest?

If you have ever fed a commercial dog food product, you know what an extruded feed looks like. Extrusion is simply the process of pushing a mix of heated feed ingredients through small holes under high pressure. You don’t see many extruded horse feeds these days, but there are some out there (two extruded Purina products are WellSolve W/C and Amplify). One of the biggest claims by manufacturers of extruded horse feed is that it is easier for horses to digest, therefore making it better for horses recovering from colic surgery. This is not exactly the case, and there's more to the story:

Purina Amplify, an extruded high-fat nugget

It is true that extrusion does increase digestibility of starch and protein as compared to certain un-processed ingredients. However, there is no strong science to back the notion than extrusion is better than other processing methods (such as pelleting) to increase digestibility. The 2007 NRC does make mention that “feeding a complete feed containing extruded ingredients was more effective at maintaining the body weight of old horses with low body condition when compared to a more traditional ration”. This statement refers to Dr. Les Bruer’s published research on Purina Equine Senior (back then, it contained Athlete, the extruded fat nugget utilized before Amplify). This is the only place in the NRC that extrusion is mentioned specific to a horse feed. The only other place it comes up is in a general discussion of the process and also in some studies looking at how different processing methods (including extrusion) affect digestibility of whole grains. The general conclusion of those studies was that the mechanical and heat treatment of certain feed ingredients (i.e. corn) through pelleting, extrusion, micronizing, or popping can increase the starch and protein digestibility as compared to un-processed ingredients. But there is no consistent evidence to show that one processing method utilizing heat is superior to any other. During the pelleting process, “raw” feed ingredients are subjected to both high temperature and moisture, a process which enhances digestibility of certain feed components. During extrusion, the final step after heat and moisture treatment is when the pellet expands as steam is released very rapidly due to a sudden drop in pressure. This creates the “puffed” physical appearance of an extruded feed. So in general terms, the primary difference between extrusion and pelleting is the final step of the process. Both processes improve the overall digestibility of raw feed ingredients as compared to whole grains, and there currently is no published evidence that one processing method is better than the other. So the decision as to whether a pelleted or extruded feed is more digestible should be made based on the formula and nutritional content of the feed itself (and the research behind that feed) and not solely on the processing method alone.

Bottom line: Processed feeds can be easier to digest than unprocessed feeds, especially for horses with poor teeth or that have gastrointestinal health issues, but there are no proven advantages of one specific processing method over another.


  1. There are different extrusion methods (wet extrusion vs. dry extrusion). The beneficial impact of dry extrusion(namely high shear-extrusion) processing is well-documented. The difference between dry extrusion and other processing method is relatively high-temperature (up to 320F), short processing time (20-30 Sec.)and high pressure which leads to better digestibility and nutrient availability of extruded ingredients. Please see the following blog for more info: http://blog.insta-pro.com/

  2. Dear Reza,

    I would be interested to to read any studies you may have showing improvements in digestibility and/or nutrient availablilty of dry extruded ingredients in horses, as the current NRC does not reference any nor are they apparent in the current literature. There is no question that certain processing methods, including both pelleting and extrusion, can be beneficial in terms of digestibility. However, the ultimate determinant of a feed's overall digestibility is the quality of all ingredients and the balance of nutrients supplied as opposed to simply how the feed was processed.