Effects of Replacing Soybean Meal Protein with <i>Chlorella vulgaris</i> Powder on the Growth and Intestinal Health of Grass Carp (<i>Ctenopharyngodon idella</i>)

Abstract

Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with enormous potential to be a protein source. However, it is poorly studied in aquatic animals. The purpose of the present study was to explore the optimum replacement ratio of C. vulgaris powder and the influence of the substitution of soybean meal with C. vulgaris on grass carp (Ctenopharyngodon idella) in terms of growth performance, intestinal integrity and the microbial community. Five isonitrogenous and isolipidic diets were formulated by replacing 0% (SM, containing 30% soybean meal), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) soybean meal with C. vulgaris. The feeding trial period lasted 8 weeks. At the end of the experimental trial, the X50 group showed higher FW, WGR and PER than the SM group (p p p ). Replacing 50% soybean meal with C. vulgaris improved the intestinal barrier integrity, as evidenced by upregulating zo-1, zo-2 and occluding transcript (p Nrf2-keap1 signaling pathway (p p tlr-4, tlr-7, tlr-8 and il-6 through the tlr pathway (p p Firmicutes and Rhodobacter (p C. vulgaris powder could promote the growth performance of grass carp by restoring intestinal morphology, increasing digestive enzyme activities, improving antioxidant properties and immunity and optimizing the microflora structure. A C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp.

Keywords

• <i>Ctenopharyngodon idella</i>
• <i>Chlorella vulgaris</i>
• growth performance
• oxidative stress
• intestinal morphology
• intestinal microflora