Effects of chelated complexes and probiotics on histological and morphometric parameters of the gastrointestinal tract of juvenile carp (Cyprinus carpio)

ABSTRACT Fish feeding is an essential technological element of aquaculture that affects fish breeding and key biological performance indicators. This research evaluated how the combined use of complex organomineral chelated compounds and Bacillus subtilis based probiotics affects several histological and morphometric parameters of the midgut of juvenile carp (Cyprinus carpio). Juvenile carp were divided into 10 groups (n = 30 per group) that received standard feed with the addition of chelated compounds and probiotics at various concentrations or standard feed alone as a control. There was no significant difference between the control and treatment groups in the height of the prismatic epithelium of the villi, but increasing the concentrations of chelated compounds and probiotics led to a significant decrease in the thickness of the muscle plate (P < 0.05) from 38.59 ± 5.36 µm in the control group to a minimum of 31.52 ± 5.99 µm and a two-fold reduction in the number of goblet cells (P < 0.05) but an increase in the goblet cell area to 58.84 ± 3.46 µm2. An increased thickness of the midgut muscle plate, enlargement of the goblet cells and enhanced mucin secretion were also observed, suggesting that these feed additives stimulate the digestive processes in fish.