Sixty-day research was conducted to investigate the effects of dietary butyric acid glyceride (BAG) on the performance of Acanthopagrus latus fingerlings (8.59 ± 0.33 g).Experimental feeds were prepared by supplementing a commercial feed (crude protein: 50%, crude lipid: 15%) with graded levels of BAG including 0 (control), 0.25% (BAG0.25), 0.5% (BAG0.5) and 1% (BAG 1). One hundred and twenty fish (10 fish in each tank) were stocked in twelve 300-L tanks then fed with the experimental feeds twice daily. Growth and feed utilization in fish fed BAG-supplemented diets were better than the control (p < 0.05). Fish fed BAG1 diet had more red and white blood cells counts than the other groups. Total immunoglobulin content and lysozyme activity in the skin mucus increased by increasing dietary BAG. Fish in BAG1 group had more skin mucosal alternative complement pathway activity than the other groups (p < 0.05). Liver catalase and glutathione S transferase activities increased in a doseresponse manner to dietary BAG level. Fish in BAG1 group showed higher liver glutathione reductase activity than the other treatments. According to the findings of this study, supplementing diet with 1% of BAG can promote growth performance and health conditions in A. latus fingerlings.

Growth behavior and production of short-chain fatty acid (SCFA) of two probiotics, Pediococcus acidilactici and Lactococcus lactis, each at 10 cfu/g (P1, L1) and 10 cfu/g (P2, L2) at different concentrations of fructooligosaccharide (FOS) [0.5% (F1), 1% (F2), and 2% (F3)] were assessed in vitro. The time to reach the maximum growth of the probiotics in all 12 treatments was between 8 to 10 h, with the highest and the lowest growth rates obtained in F1L1P1 (0.34 ± 0.02 OD) and F3L1P1 (0.31 ± 0.05 OD) treatments, respectively. The shortest and the longest generation times were seen in F1L1P1 (112 ± 1.5 min) and F2L1P1 (231 ± 0.5 min) treatments, respectively. The highest and the lowest levels of SCFA production were found in F1L1P1 (17.94 ± 0.74 mg/L) and F3L1P1 (12.98 ± 0.85 mg/L) treatments, respectively. The three synbiotics with the highest SCFA production were then fed to Caspian roach (Rutilus frisii kutum) fry weighing 0.75 ± 0.02 g at 28 °C for 60 days, to assess growth performance and enzymatic activity. The best growth performance in terms of weight gain (WG), protein efficiency ratio (PER), net protein utilization (NPU), and food conversion ratio (FCR) were seen with F1L1P1. In addition, the highest activity levels of the digestive enzymes chymotrypsin, lipase, and amylase were obtained with F1P1L1. The correlation of these in vitro and in vivo data demonstrated that oral application of these two probiotics each at 10 cfu/g feed plus 0.5% FOS can improve growth and gut enzyme activity of Caspian roach fry.