This study investigated the effect of crude protein (CP) and non-essential amino acids (NEAA) supplementation on growth performance and gut health of nursery pigs. Ninety weaned pigs (22 days old; 7.5 ± 0.7 kg BW; AGPIC 415 × Camborough) barrows and gilts, were distributed in a randomized complete block design (BW as block) to three dietary treatments fed for 14 days: 1) 24% CP, 2) 18% CP, and 3) 18% CP + NEAA, including 5 g/kg L-arginine and 10 g/kg L-glutamate + L-glutamine (AminoGut, Ajinomoto, São Paulo, Brazil). There were ten replicates per treatment and three pigs per pen. A corn-soybean meal-based diet was formulated to have 3,400 kcal/kg of metabolizable energy and 1.45 g/kg of standardized ileal digestible lysine. Crystalline amino acids, L-Lys, L-Thr, DL-Met, L-Trp, L-Val, L-Ile, L-His, and L-Leu were used (if necessary) to satisfy the ideal amino acid profile according to the Brazilian Tables for Poultry and Swine (Rostagno et al., 2017). On day 14, pigs were weighed and then euthanized to collect duodenum, jejunum, and ileum tissue. Growth performance, diarrhea incidence, intestinal morphology, goblet cells, and Peyer’s patches were evaluated. Data were analyzed using the Mixed procedure in SAS 9.4 and means were compared by Tukey’s test. Pigs fed 24% CP diet had improved (P < 0.05) G:F compared to 18% CP and 18% CP + NEAA (Table 1). There was no effect (P > 0.05) of dietary treatments on ADFI, ADG, BW, and diarrhea incidence. In the duodenum, pigs fed 18% CP + NEAA diets had greater (P < 0.05) villus height compared to the 24% CP and 18% CP (427 to 381 and 383 µm). Moreover, goblet cells proportion in pigs fed 24% CP and 18% CP + NEAA diets were higher (P < 0.05) than that of 18% CP (53.2 and 53.4 to 45.3%). In the jejunum, pigs fed 18% CP + NEAA diet had reduced (P < 0.05) crypt depth than those fed 24% CP (161 and 141 µm), whereas pigs fed 18% CP presented intermediate results (144 µm). In the ileum, pigs fed the 24% CP diets presented a higher (P < 0.05) number of Peyer’s patches compared to 18% CP and 18% CP + NEAA (48 to 38 and 41 units).
In conclusion, nursery pigs fed 24% CP diets presented improved G:F compared to those fed 18% CP or 18% CP + NEAA. However, pigs fed the 18% + NEAA diets presented better gut health compared to 24% CP or 18% CP.