Effects of allicin supplementation on the growth performance, biochemical composition and immune responses of ivory shell (Babylonia areolata)

In the present study, the effects of different levels of allicin supplementation (0.00 % as control, 0.30 %, 0.45 %, 0.60 %, 0.75 %, and 0.90 %) on the growth performance, biochemical composition and immune capacity of ivory shells (Babylonia areolata) were investigated. Allicin supplementation in the daily diet significantly enhanced growth performance, with the highest specific growth rates observed at concentrations ranging from 0.75 % to 0.90 % (2.18–2.20 %/d), and the lowest feed conversion ratio (1.39) recorded at 0.60 %. Correspondingly, mRNA expression levels of two appetite-related genes, Orexin and Neuropeptide Y (NPY), in the hepatopancreas significantly increased, while the expression of the appetite-suppressing gene Leptin significantly decreased with increasing allicin supplementation. The amounts of almost all detected fatty acids significantly increased when ivory shells were fed diets supplemented with allicin, while their profiles varied, showing increases in C20:1n9 and C22:6n3 (DHA), and decreases in C16:0, C18:2n6, and C20:4n6 (ARA). Lipase activities in both the intestine and hepatopancreas significantly increased in the allicin-supplemented groups, with peak values observed at 0.90 % and 0.75 % allicin supplementation, respectively (3.64 U/g prot in the intestine and 9.52 U/g prot in the hepatopancreas). Allicin supplementation improved the antioxidant and antimicrobial abilities of ivory shells, leading to increased activities of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT) and lysozyme in the hepatopancreas, and reduced malondialdehyde (MDA) contents. Similar trends were observed in mRNA levels of SOD, CAT and lysozyme genes. In conclusion, moderate allicin supplementation in artificial diets (approximately 0.75 %-0.90 %) can significantly enhance growth performance, increase muscle lipid content, and boost immune capabilities of ivory shells.