Effect of the Addition of Humic Substances on Morphometric Analysis and Number of Goblet Cells in the Intestinal Mucosa of Broiler Chickens

SIMPLE SUMMARY: During recent decades, researchers have investigated humic substances (HS) as a potential replacement for, or reduction in the use of, growth-promoting antibiotics (GPA) in chicken diets. Several mechanisms of action have been proposed to explain the improvements in productive and health responses observed in broiler chicks given HS, such as stabilizers of the intestinal flora, effects on the digestive system similar to acidifiers, and the creation of protective layers on the epithelial mucous membrane of the digestive tract, but none of these theories have been demonstrated. Whether HS affects the histology and number of goblet cells (GC) in the intestine of broilers kept under stable digestive conditions and under abrupt changes in diet was studied in this research. From 14 to 38 days, HS-fed broilers had a similar FCR to AGP-fed broilers, but there was no clear trend in the effect of HS on the morphometry of villi in broilers raised under stable digestive conditions and following abrupt dietary changes. Under stable digestive conditions and after experiencing sudden dietary changes, the number of GC in the jejunum of HS-fed broilers behaves closely to that of AGP-fed broilers. These findings may aid in explaining the mechanism of action of HS. ABSTRACT: The mechanisms of action of humic substances (HS) as growth promoters in poultry are unknown. In this study, the productive performance, histology, and number of goblet cells (GC) in the intestinal villi of broilers under steady-state digestive conditions and under abrupt changes in diet with the addition of HS was evaluated. Broilers housed individually were offered three treatments from 14–28 days: 1 = diet with white corn/soybean meal, without growth promoter antibiotics (nonGPA); 2 = with GPA (GPA); and 3 = with 0.3% HS. At day 28, two diets were suddenly introduced: (A) white corn/soybean meal plus dried distillers’ grains with solubles (DDGS); and (B) white/blue corn/soybean meal/DDGS, keeping the three original treatments. Diets A and B were also exchanged on day 37. FCR was lower with GPA and HS compared to nonGPA from 14–38 days (p < 0.05); at day 28, under steady-state digestive conditions, HS had a similar effect to GPA on the histology and GC number in the jejunum villi. The number of GC in the jejunum of HS-fed broilers on days 29 and 38, after diet changes, behaves similarly to that of AGP-fed broilers (p > 0.05). HS appears to strengthen the mucosal protection of the epithelium of the intestine.