ISSUE FOCUS FEED & ADDITIVE MAGAZINE November 2025 33 curring after feed intake should be kept as short as possible to minimize the risk of pathogenic bacteria surviving and migrating into the duodenum. The ABC is an analytical parameter that is determined in vitro by adding acid (or base) to a raw material or feed to achieve a preset pH. This preset pH correlates with the optimal pH for the animal’s digestive enzymes. It is generally accepted that pH 4.0 is a good reference value for young piglets, because this pH is the maximum value for the proteolytic activity of pepsin, and it is sufficiently low to allow for good (protein) digestion and pH-based pathogen suppression. Therefore, most nutritionists consider ABC-4 (i.e. the amount of acid or base that must be added to an ingredient or feed to reach pH 4.0) to be the setpoint practically relevant for piglets. ABC-4 values can be found in literature and are expressed in milli-equivalents of acid per kg (meq H+/kg). Materials consuming acid have positive ABC-4 values, those adding acid(ity) have negative values. AIM LOW Limited gastric acid production is typical for young piglets, so ABC-4 values are most relevant in young animal nutrition. It is generally acknowledged that the gastric acid production by a piglet may remain insufficient (pH>3.5-4.0 in fasting state) until 6-7 weeks of age, and suboptimal (pH>2.5-3.0 in fasting state) until approximately 60 days (8-9 weeks). Research by F. Molist et al. of Schothorst Feed Research (SFR, NL) and Stas et al. of Kansas State University establishes target ABC-4 values of a complete feed as a function of the animal’s age (Table 1). When formulating piglet diets, nutritionists can assume that ABC-4 values of raw materials are additive – i.e., that the ABC-4 value of a complete feed can be predicted with sufficient accuracy by the weighed sum of the ABC-4 values of the individual raw materials present in the feed. Therefore, a good knowledge of the ABC-4 values of the different classes of raw materials allows nutritionists to steer the dietary ABC-4 value of a diet towards the target value. NATURAL = VARIABLE Pure raw materials containing one type of molecule (e.g., salt NaCl, sodium bicarbonate NaHCO3, fumaric acid, calcium propionate) have a constant chemical composition and predictable ABC-4 values with low batch-to-batch variability. For these raw materials, differences in ABC-4 values result mainly from their level of concentration – i.e., from the presence of other compounds that dilute the ingredient without having a significant buffering capacity themselves (e.g., water, Target ABC-4 values (meq H+/kg) Piglet age < 7 weeks 7-12 weeks Table 1. Target ABC-4 values of piglet feed SFR Kansas State 150-250 200-300 250-300 Photo: Dusan Petkovic | Shutterstock
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