Effects of Chitosan-Coated Microdiet on Dietary Physical Properties, Growth Performance, Digestive Enzyme Activities, Antioxidant Capacity, and Inflammation Response of Large Yellow Croaker (Larimichthys crocea) Larvae

Abstract

A 30-day feeding trial was designed to investigate the physical properties of chitosan-coated microdiet (CCD) and the effect of CCD on survival, growth performance, activities of digestive enzymes, intestinal development, antioxidant capacity, and inflammatory response of large yellow croaker larvae (initial weight: <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mn>3.81</a:mn> <a:mo>±</a:mo> <a:mn>0.20</a:mn> <a:mtext> </a:mtext> <a:mtext>mg</a:mtext> </a:math> ). Four isonitrogenous (50% crude protein) and isolipidic (20% crude lipid) microdiets were prepared with different concentrations of chitosan wall material by spray drying method (0.00%, 0.30%, 0.60%, and 0.90%, weight (chitosan) : volume (acetic acid)). Results showed that the lipid encapsulation efficiency (control: 60.52%, Diet1: 84.63%, Diet2: 88.06%, Diet3: 88.65%) and nitrogen retention efficiency (control: 63.76%, Diet1: 76.14%, Diet2: 79.52%, Diet3: 84.68%) correlated positively with the concentration of wall material ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mi>P</c:mi> <c:mo>&lt;</c:mo> <c:mn>0.05</c:mn> </c:math> ). Furthermore, the loss rate of CCD was significantly lower than the uncoated diet. Larvae fed the diet with 0.60% CCD had significantly higher specific growth rate (13.52 and 9.95%/day) and survival rate (14.73 and 12.58%) compared to the control group ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>P</e:mi> <e:mo>&lt;</e:mo> <e:mn>0.05</e:mn> </e:math> ). Larvae fed the diet with 0.30% CCD had significantly higher trypsin activity in pancreatic segments than the control group (4.47 and 3.05 U/mg protein) ( <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:mi>P</g:mi> <g:mo>&lt;</g:mo> <g:mn>0.05</g:mn> </g:math> ). Larvae fed the diet with 0.60% CCD had significantly higher activity of leucine aminopeptidase (7.29 and 4.77 mU/mg protein) and alkaline phosphatase (83.37 and 46.09 U/mg protein) in the brush border membrane than those of the control group ( <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:mi>P</i:mi> <i:mo>&lt;</i:mo> <i:mn>0.05</i:mn> </i:math> ). The intestinal epithelial proliferation- and differentiation-related factors (zo-1, zo-2, and pcna) in larvae fed the diet with 0.30% CCD had higher expression than those of the control group ( <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M6"> <k:mi>P</k:mi> <k:mo>&lt;</k:mo> <k:mn>0.05</k:mn> </k:math> ). When the concentration of wall material reached 0.90%, the larvae had significantly higher superoxide dismutase activity than that of the control group (27.27 and 13.72 U/mg protein) ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" id="M7"> <m:mi>P</m:mi> <m:mo>&lt;</m:mo> <m:mn>0.05</m:mn> </m:math> ). Meanwhile, malondialdehyde contents were significantly lower in larvae fed the diet with 0.90% CCD than that of the control group (8.79 and 6.79 nmol/mg protein) ( <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" id="M8"> <o:mi>P</o:mi> <o:mo>&lt;</o:mo> <o:mn>0.05</o:mn> </o:math> ). 0.30%~0.60% CCD significantly increased the activity of total nitric oxide synthase (2.31, 2.60, and 2.05 mU/mg protein) and inducible nitric oxide synthase (1.91, 2.01, and 1.63 mU/mg protein) and had significantly higher transcriptional levels of inflammatory factor genes (il-1β, tnf-α, and il-6) than those of the control group ( <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" id="M9"> <q:mi>P</q:mi> <q:mo>&lt;</q:mo> <q:mn>0.05</q:mn> </q:math> ). The results indicated chitosan-coated microdiet had great potential in feeding large yellow croaker larvae in addition to reducing nutrition loss.