Effect of humic acid substances on proteolytic activity in intestine, digestibility of crude protein and protein content in the blood of broiler chickens

Anotace: The objective of the study was to investigate the effects of dietary intake of humic substances (HS) on the proteolytic activity and the digestibility of crude protein (CP) measured as the apparent assimilable mass coefficient of CP corrected for protein catabolism (AMCN) in the intestine as well as on the total protein and albumin content in the serum of broiler chickens (Cobb 500, n=120). Chickens (groups A, B, C / negative control) were fed with mixtures with CP (g.kg-1 DM) – Hyd1 230.20 (d 1-7), Hyd2 222.20 (d 8-28), Hyd3 209.40 (d 29-37) for 37 days. The humic substances were added into diets of experimental groups in the feed additive according to the content of humic/fulvic acids (HA/FA; g.kg-1) A 4.55/0.35, B 3.99/0.35, C 2.85/0.25. The body weights and feed consumption were measured once a week. The average daily weight gains and the feed conversion ratio were calculated. The dietary intake of HS had a positive effect on the increase of proteolytic activities in the intestinal apparatus and caused the significant enhancement of AMCN of birds from experimental groups on days 17, 24 and 31. However, the values of the total protein and the albumin in the serum were significantly decreased in the groups after intake of HA/FA 4.55/0.35 or 3.99/0.35 in the feed.