Effects of paraformic acid supplementation, as an antibiotic replacement, on growth performance, intestinal morphology and gut microbiota of nursery pigs

Abstract

49 A total of 150 crossbred male pigs [21±1 days old; 8.85±0.15 Kg body weight (BW)] were randomly assigned to five 50 dietary treatments with five replicates per treatment and six pigs per pen to evaluate the effect of paraformic acid 51 (PFA), as a substitute to antibiotics, on growth performance, intestinal morphology, and gut microbiota of nursery 52 pigs. The treatments were: 1) NC: nutrient adequate control diet; 2) PFA1: similar to NC plus 0.30% PFA; 3) PFA2: 53 similar to NC plus 0.60% PFA; 4) PFA3: similar to NC plus 1.0% PFA; and 5) PC: similar to NC plus 0.15% of 54 chlortetracycline. Pigs were fed the same nutritional profile during the two-phase feeding regime [phase 1 (P1; d 0– 55 14), and phase 2 (P2; d 15–30)]. Initial BW, and BW and feed disappearance at the end of each phase were recorded 56 to calculate average daily feed intake (ADFI), average daily gain (ADG), and feed to gain ratio (F: G). The Fecal score 57 was determined at the end of P1, while the intestinal morphology and microbiota analysis were performed at the end 58 of P2. Pigs fed PFA2 had higher ADG than those fed NC in P1. A quadratic response was found in the overall phase 59 1 and phase 2 (P1&2) with the highest ADG in pigs fed PFA2 ( p < 0.05). Pigs fed PC had the highest ADFI during 60 P2 and overall P1&2 ( p < 0.05). The PFA2 group had the lowest F:G ratio among treatments in P1 and P2, with a 61 quadratic response in the overall P1&2 ( p < 0.05). Pigs fed PFA1, PFA2, PFA3, and PC showed better fecal 62 consistency than NC ( p < 0.05). No differences were found in intestinal morphology among treatments. PFA groups 63 supplementation modulated the relative abundance of Lactobacillus and Streptococcus in the jejunum. In the cecum, 64 PFA2 had a higher relative abundance of Prevotella when compared to NC, but lower than PC. In addition, pigs fed 65 the NC diet had higher abundance of Treponema and Methanobrevibacter than other treatments. In conclusion, the 66 supplementation of 0.6% PFA improved growth performance and modulated gut microbiota in nursery pigs. 67