K. Burlakova*, H. Lukanov

Department of Animal Husbandry – Non-ruminants and Special Industries, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 4 May 2026; accepted for publication 2 June 2026)

*e-mail: katerina.burlakova@trakia-uni.bg

Abstract. The search for effective nutritional strategies to maintain gut health in intensive pig production is essential for sustainable farming. This study evaluated the acidifying and microbiota-modulating effects of 0.03% protected sodium butyrate (PSB) in finishing pigs. A total of 160 hybrid pigs (90 days of age; 42.5 kg average body weight) were allocated to a control group (basal diet) and an experimental group (basal diet + PSB) for 70 days. At slaughter, pH and microbial populations (Lactobacillus spp., Escherichia coli, coliform bacteria, and total count at 37℃) were analyzed. PSB supplementation did not significantly affect pH or microbial profiles in the stomach and small intestine (P>0.05). However, in the large intestine, PSB significantly reduced luminal pH (6.20 vs. 6.37; P=0.04) and decreased populations of Escherichia coli (P=0.004) and coliform bacteria (P=0.045), while increasing Lactobacillus spp. (P=0.045). Correlation analysis showed that lower pH and higher Lactobacillus spp. levels were associated with reduced levels of opportunistic bacteria. These findings indicate that PSB promotes acidification of the distal gastrointestinal tract and supports a more favorable microbial balance, highlighting its potential as a nutritional strategy for improving gut health in finishing pigs.