ISSUE FOCUS FEED & ADDITIVE MAGAZINE October 2024 31 OA SUPPORT STOMACH ACIDIFICATION – WHAT STUDIES SHOW Animals’ digestive enzymes degrade feed nutrients into absorbable molecules. Both the activity of these enzymes and the microbiota population in the GIT are influenced by pH. The conversion of pepsinogen into pepsin, the enzyme that digests protein, is pH dependent, and the conversion process occurs rapidly when the pH is between 2.0-3.5.1 A low pH - below 4- delivers a bacteriostatic effect against many pathogenic bacteria including E. coli, Salmonella, and Clostridium. Young animals’ present special challenges as their GITs are still immature, especially in terms of pH. Below, we look at some OA studies Trouw Nutrition conducted involving broiler and piglet diets. Broilers: In the week following hatch, the secretion and activity of digestive enzymes and the surface area for absorption are limiting factors. These limitations are overcome as the birds grow older. Different authors have observed that the GIT pH undergoes changes during the production cycle.2,3 The pH in the crop, gizzard, proventriculus, and small intestine slowly declines from day 0 to day 7. This decline is followed by an increase from d 14 to d 42. Although digestive secretions and HCl production are expected to increase as the bird ages, the pH increase beyond day 14 is probably a reflection of the broiler’s increased consumption of feed with neutral pH. The feed’s buffer capacity is also a major determinant of intestinal pH. Trial takeaway: A 35-days study performed by Trouw Nutrition tracked the GIT pH of broilers and showed that the SWA reduced the pH in the crop, proventriculus, and duodenum (Table 1). Piglets: In suckling piglets, the principal source of stomach acidity is the bacterial fermentation of the lactose in sow’s milk into lactic acid (which inhibits HCl secretion). However, at weaning, the stomach pH is high, often above pH 5.0. In the first weeks after weaning, HCl production is not yet sufficient, and pepsin activity only begins to increase when piglets reach 5-6 weeks of age (5.7 vs 17.0 U/g of mucosa).4,5 Factors causing this situation include the piglet’s dietary change from milk to solid feed (reduction of lactic acid and slow production of HCl), the change in the pattern of feed intake (consumption of large meals at
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