Dietary supplementation of garlic (Allium sativum L.) extract enhances haematological, humoral immune responses and disease resistance of Mugil cephalus Linnaeus 1758, larvae against Photobacterium damselae

This study was carried out to investigate the effect of dietary supplementation of garlic (Allium sativum) extract on growth parameters and hematological parameters and immune system response of Mugil cephalus larvae encountered with Photobacterium damselae. Two hundred and forty M. cephalus larvae with a mean weight of 5g were randomly divided into 12 equal groups, each containing 3 replicates. Fish were fed with diets containing 50, 100 and 200mg garlic extract/Kg of food for 8 weeks. Based on the results, significant difference was observed comparing final weight, specific growth rate (SGR), daily growth rate (DGR), protein efficiency ratio (PER) and feed conversion ratio (FCR) of 100 and 200mg garlic extract/Kg of food treatments and other treatments (p<0.05). Also, in 100 mg garlic extract/Kg treatment, red and white blood cells, hemoglobin, PCV counts, globulin, total protein and albumin were significantly higher than those of control and 200mg garlic extract/Kg of food (p<0.05). The immune indices (lysozyme activity, serum total immunoglobulin (Ig) content, phagocytic activity and respiratory burst activity) significantly increased in 100mg garlic extract/Kg treatment compared to those of other treatments, especially control (p<0.05). The results revealed that treatments containing 50 and 100mg garlic extract/Kg food had the highest survival after challenging with P. damselae compared to survival of other treatments (p<0.05). In conclusion, results suggested that dietary administration of garlic extract; especially in 100mg garlic extract/Kg concentration is recommended for enhancing growth performance, nutritional function, immunity and resistance of M. cephalus larvae against the bacterium P. damselae.