By Joel DeRouchey, Ethan Stas, Mike Tokach, Jason Woodworth, Bob Goodband and Jordan Gebhardt of Kansas State University
The use of diet acidifiers to aid newly weaned pigs in reducing the digestive tract pH has become a routine practice in most starter diets. Acidifiers are believed to enhance growth performance via pH reduction in the digestive tract, which improves nutrient digestibility and lowering of pathogenic bacteria.
What are in-feed acids?
Acidifiers are compounds classified as organic or inorganic acids. Organic acids include formic, fumaric, lactic, benzoic, propionic and citric acids. Inorganic acids include hydrochloric, sulfuric and phosphoric acids. Salts of acids also have been used as acidifiers, including calcium-formate, potassium-diformate, sodium-diformate, and sodium-fumarate. Blends of acidifiers are often commercially available because organic and inorganic acids may have a synergistic effect. In addition, some commercial acidifiers contain protected acids that are coated with fatty acids or other molecules, mainly to allow the release of the acid in a targeted location in the gut with the goal to improve effectiveness.
Buffering capacity of the diet
Starter diets need to be formulated in a manner to allow the acidifiers to be effective. This means the diet buffering capacity must be low enough that the in-feed acid can do its job. Because the newly weaned pig has a limited ability to produce hydrochloric acid to lower the feed pH for optimal digestion, formulating with ingredients low in buffering capacity is ideal to aid in digestion and inhibit pathogenic bacteria growth. In fact, a concept called acid-binding capacity-4 (ABC-4) is now being used to assess an ingredient buffering capacity. ABC-4 is the amount of acid required to lower an ingredient to a pH of 4. The use of low acid-binding ingredients or avoidance of high buffering ingredients can help maintain a more desirable acidic environment in the stomach and small intestine.
Ingredient influence on ABC-4
Minerals, such as limestone and zinc oxide, have a ABC-4 value over 200 times higher than most cereal grains, such as corn. Also, specialty lactose sources of whey powder and whey permeate are higher than that of crystalline lactose. There is also a wide variation in ABC-4 values for specialty animal and vegetable protein sources that can either raise or lower the ABC-4 when replacing soybean meal. However, in-feed acids often have a negative ABC-4 value which can significantly decrease diet buffering capacity, thus a mode of action for their use. Still, if a diet contains a high level of calcium, zinc oxide and other high buffering ingredients, many in-feed acids will not have enough pH reducing ability to provide any benefit to the newly weaned pig.
Click here to learn more about in-feed acidifiers and ABC-4 values of common feed ingredients.
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