Dietary Sodium Butyrate Changed Intestinal Histology and Microbiota of Rainbow Trout (Oncorhynchus mykiss), but Did Not Promote Growth and Nutrient Utilization
Xia Lin, Chunyan Zhang, Kailin Cao, Zhendong Li, Zhongshen Zhao, Xiaoqin Li, Xiangjun Leng
Abstract
The study investigated the effects of dietary sodium butyrate (SB) on the growth performance, nutrient utilization, intestinal histology, and microbiota of rainbow trout (Oncorhynchus mykiss). A high fishmeal diet and a low fishmeal diet were formulated to contain 200 g/kg or 100 g/kg fishmeal, respectively. Coated SB (50%) was supplemented to each of the diets at levels of 0, 1.0, and 2.0 g/kg to create 6 diets. The diets were fed to rainbow trout with initial body weight of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mn>29.9</a:mn> <a:mo>±</a:mo> <a:mn>0.2</a:mn> <a:mtext> </a:mtext> </a:math> g for 8 weeks. Compared to the high fishmeal group, the low fishmeal group showed significantly lower weight gain (WG), intestine muscle thickness, and significantly higher feed conversion ratio (FCR) and amylase activity ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mi>P</c:mi> <c:mo><</c:mo> <c:mn>0.05</c:mn> </c:math> ). The supplementation of SB in high or low fishmeal diet did not significantly affect the WG, FCR, protein retention, and the digestibility of dry matter and crude protein ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>P</e:mi> <e:mo>></e:mo> <e:mn>0.05</e:mn> </e:math> ). The supplementation of 2.0 g/kg SB in low fishmeal diet significantly increased the villus height, villus width, and muscular thickness, while the supplementation of 2.0 g/kg SB in high fishmeal diet also significantly increased the intestinal villus height ( <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:mi>P</g:mi> <g:mo><</g:mo> <g:mn>0.05</g:mn> </g:math> ). In intestinal microbiota, the supplementation of 2.0 g/kg SB significantly increased the abundance of Proteobacteria and Aeromonas, and decreased the abundance of Firmicutes and Mycoplasma ( <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:mi>P</i:mi> <i:mo><</i:mo> <i:mn>0.05</i:mn> </i:math> ), but the flora at genus and phylum level were not affected by SB supplementation in low fishmeal diet ( <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M6"> <k:mi>P</k:mi> <k:mo>></k:mo> <k:mn>0.05</k:mn> </k:math> ). In conclusion, the addition of SB in diets containing 100 or 200 g/kg fishmeal did not enhance the growth performance and nutrient utilization of rainbow trout, but improved intestinal morphology and changed intestinal microbial flora.