Effect of Fortified Feed with Phyto-Extract on the First Physical Barrier (Mucus) of Labeo rohita

SIMPLE SUMMARY: Pathogens of fish are a serious issue faced by farmers and a great threat to the country’s economy. Overuse of antibiotics leads to antibiotic-resistant strains of the bacterial pathogens; residues of the antibiotics also accumulate in the tissue of the fish and are responsible for environmental problems. Therefore, the use of antibiotic alternatives should be explored as a new approach to immunotherapy to prevent or to cure preexisting infections. Previous research has concluded that the use of herbal extracts enhances the immunity of fish against several fish pathogens such as bacteria and other protozoon parasites. This study aimed to evaluate the effect of two different fortified feeds with different concentrations of Withania coagulans and Zingiber officinale on the fish mucus of Labeo rohita. The mucus was tested against five pathogenic bacteria in-vitro while fish was tested against the ectoparasite Lernaea (in-vivo). Our result showed that Z. officinale proves an efficient immune stimulator for the L. rohita against the tested organism (both in vivo and in vitro). Hence, it can be used as an effective solution against the emerging diseases of cultured fish. ABSTRACT: The aim of the current study was to assess the effect of two different fortified feeds with different concentrations of two important medicinal plants (Withania coagulans and Zingiber officinale) on the mucosal immunity of Labeo rohita. After a dietary intervention, mucus was tested against five pathogenic bacteria (in-vitro), while experimental fish were tested against the ectoparasite (Lernaea) (in-vivo). Our results revealed that all fish groups fed with different concentrations (1, 1.5, and 2%) of Z. officinale had low molecular weight proteins and did not develop any significant signs of parasitic infection, with low mortality rate; whereas the groups that were fed with W. coagulans (particularly with 1% and 2%), including a control group, developed rapid signs of infection with high mortality rate. The highest hemagglutination titer value was recorded for the fish fed with 1% and 1.5% of Z. officinale. The lowest value was found for the fish fed with 2% of W. coagulans. The mucus of all fish of fortified groups was active and inhibited the growth of tested bacterial pathogens as compared to the control group. Further, Z. officinale groups showed greater efficacy against bacteria as compared to the W. coagulans groups. In conclusion, Z. officinale can be considered as a potential and functional ingredient in aquaculture feed. Furthermore, future studies should be conducted to investigate more details on the subject.