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Laser light scattering (LLS) and conductivity experiments were performed to investigate the effect of counter ions on the conformation of polycarboxylate comb-like copolymers (PCEs) in aqueous solutions. The addition of monovalent ions (i.e., Na+, K+) to dilute polycarboxylate comb-like copolymer solutions induced a slight shrinking of the molecular chains because of the screening of electrostatic intramolecular repulsion. Varying complexation phenomena, such as the formation of intramolecular complexation at certain Ca2+ concentrations and a transition between intermolecular and intramolecular complexations at different Ca2+ concentrations were closely associated with Ca2+ concentration. Therefore, Ca2+ exerted a more complex influence on the conformation of PCEs with side chains containing polyethylene oxide (PEO) with different grafting densities. In addition, various combination types of Ca2+ with carboxylic groups were confirmed by theoretical simulation.

Laser light scattering (LLS) and conductivity experiments were performed to investigate the effect of counter ions on the conformation of polycarboxylate comb-like copolymers (PCEs) in aqueous solutions. The addition of monovalent ions (i.e., Na+, K+) to dilute polycarboxylate comb-like copolymer solutions induced a slight shrinking of the molecular chains because of the screening of electrostatic intramolecular repulsion. Varying complexation phenomena, such as the formation of intramolecular complexation at certain Ca2+ concentrations and a transition between intermolecular and intramolecular complexations at different Ca2+ concentrations were closely associated with Ca2+ concentration. Therefore, Ca2+ exerted a more complex influence on the conformation of PCEs with side chains containing polyethylene oxide (PEO) with different grafting densities. In addition, various combination types of Ca2+ with carboxylic groups were confirmed by theoretical simulation.

This 8 week feeding trial evaluated the effects of three feeding stimulants (FS) on feed intake, growth performance, body composition, serum biochemical parameters, and digestive enzyme activities for juvenile GIFT tilapia fed low fishmeal diets. Four test diets were supplemented with 0, 16 g/kg taurine (Tau), 0.4 g/kg mixed nucleotides (Mix-NT), and 30 g/kg squid liver paste (SQLP) respectively, and fed to juvenile GIFT strain of Oreochromis niloticus (3.34±0.01 g). The results showed that feed intake (FI) significantly increased with SQLP. Specific growth rate (SGR) in fish fed SQLP or Mix-NT diet was significantly higher than that of the Tau and control group. The feed conversion ratio (FCR) ranged from 1.34 in the group fed Mix-NT to 1.50 in the group fed Tau, with no significant differences compared to the control group. Three feeding stimulants had no significant influence on whole body composition of tilapia. Fish fed Mix-NT diet showed significantly higher intestinal protease activity and intestinal amylase activity than that of other groups. High-density lipoprotein content in serum was significantly higher in fish fed SQLP diet than that of other groups. In conclusion, supplementation of 0.4 g/kg mixed nucleotides or 30 g/kg squid liver paste in low fishmeal diets could provide better growth performance for juvenile tilapia, and SQLP could act as an effective FS under these conditions. Supplementation of Mix-NT could reduce the FCR in these fish.