Effects of different feeding patterns on growth, enzyme activity, and intestinal microbiome of the juvenile Pacific abalone Haliotis discus hannai

In northern China, the predominant food sources for abalone farming include fresh kelp, salted kelp, and formulated diets, and abalone can also endure prolonged starvation when food is scarce. While there is a dearth of comprehensive investigation into the effects of these feeding patterns on the temporal dynamics of enzyme activity, and intestinal microbiome of abalone. In this study, a total of 3600 juvenile Pacific abalones were allocated to 12 tanks, randomly divided into four groups based on the feeding patterns: fresh kelp (labeled as FK), salted kelp (SK), formulated feed (FF), and starved group (S). After a 60-day feeding trial, the results showed that abalone in the FK, SK, and FF groups exhibited significant positive effects on both weight and shell growth compared to the S group (P<0.05). Notably, the FF group displayed the highest values of the growth performance. The activity of digestive enzymes and antioxidant enzymes in the FF group had an up-regulated trend over the course of feeding trial, whereas amylase and lipase activity in abalone declined along with starvation. Moreover, the microbial Shannon index showed an overall decreasing trend over time in the FF, FK, and SK groups except for the S group. The ANOSIM analysis revealed that both feeding pattern and cultivating time significantly influenced the structure of the microbial communities. Across the feeding trial, Proteobacteria, Fusobacteriota, and Firmicutes were identified as the dominant phyla in the intestinal microbiome of abalone under different feeding patterns. The core genera were Psychrilyobacter, Mycoplasma, and Vibrio. Additionally, the neutral model analysis revealed that stochastic processes both play a key role in shaping the assembly of microbial communities in different feeding patterns. This study could offer valuable insights into the impact of different feeding patterns on growth and physiology of abalone, thereby contributing to the enhancement of management strategies in the northern Chinese abalone aquaculture industry.