Dry and Wet pet feed extruder machines: How Do They Differ in Feed Pellet Quality and Nutritional Retention?

In terms of pellet physical quality, dry extrusion produces a harder, more brittle pellet, while wet extrusion produces a softer, more porous pellet. In dry extrusion, the raw material has low moisture content and generates intense frictional heat, resulting in a dense, porous internal structure with a hardness typically between 30-50 N. The pellets are highly intact and not easily broken, making them suitable for producing adult dog chew food and floating aquatic feed. These pellets can maintain their shape even after soaking in water for 2 hours, reducing feed waste. Wet extrusion, due to the higher moisture content of the raw material, produces a pellet with larger and more uniform internal pores, a hardness of only 15-30 N, and a softer, more chewable texture, making it suitable for puppies, senior dogs, and young livestock. It also facilitates subsequent coating with oils and other nutrients.

Nutrient retention is the core difference between the two, especially for heat-sensitive components. Dry extrusion involves a longer duration of high temperatures (10-20 seconds), and local temperatures can exceed 160°C, resulting in a retention rate of only 50%-70% for heat-sensitive nutrients such as vitamin E and B vitamins. Adding probiotics to raw materials reduces the number of live bacteria by over 90% after dry processing. Wet extruders use steam heating, resulting in more stable temperature control (100-140℃), shorter heating time (5-10 seconds), and increased retention of heat-sensitive nutrients to 80%-90%. Data from a test shows that, with the same formula, dog food produced by wet extruders has 25% higher vitamin E content and more than 10 times the number of live probiotics compared to dry extruders.

Wet extruders also have advantages in raw material adaptability and finished product uniformity. Dry extruders are sensitive to raw material moisture; uneven mixing leading to localized high-moisture areas can cause over-expansion and scorching, while localized low-moisture areas result in under-expansion and excessively hard pellets. Wet extruders, through external water replenishment and steam regulation, can control the overall raw material moisture within a stable range. Even with large initial moisture fluctuations, steam compensation can achieve uniform expansion. For example, when producing feed by mixing meat meal and grains, dry extruders are prone to poor puffing in areas where the meat meal clumps, while the steam in wet extruders allows the meat meal and grains to fully blend, resulting in a more even distribution of nutrients in the finished product.

The digestibility and absorption rate of the finished product also vary depending on the processing method. Feed produced by wet extruders can achieve a starch gelatinization rate of over 90%, and protein denaturation is more complete, resulting in a 10%-15% higher digestibility and absorption rate for dogs compared to dry products. Pets that regularly consume wet-processed feed experience a reduction of approximately 20% in fecal volume, indicating more efficient nutrient utilization. Producers need to choose based on product positioning: for producing ordinary, economical feed, dry extruders can meet basic needs; for producing high-end, nutritionally balanced feed, the quality advantages of wet extruders are indispensable.

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