BACKGROUND: Occurrence of resistance against antibioticsand inadequate efficacy of some vaccines necessitates studies ofnatural immunostimulators in aquaculture. Shrimps shell derivedfrom Chitosan can be used as immune stimulators in fish.OBJECTIVES: In this study, the effects of oral administration ofchitosan, derived from shrimp shell, on some immune responsesand disease resistance in Cyprinus carpio were studied. METHODS:Three hundred healthy fish weighing 42.4+8.1 g were divided into4 equal groups: the first group (G10) was fed with foodsupplemented with 10 mg kg-1 chitosan, the second (G5) and thirdgroups (G2.5) were fed with food supplemented with 5 mg kg-1 and2.5 mg kg-1, respectively. The control group was fed with basal feed(without chitosan). All groups were treated for 60 days. Bloodsamples were taken on 0, 20, 40, and 60 days post- experiment; Inaddition, some immunological indices, including serum lysozymeactivity, serum bactericidal activity, Nitro Blue Tetrazolium (NBT)reduction activity, serum proteins, white blood cell count (WBC),and differentiated count were measured. At the end of the treatment,fish were challenged with live Aeromonas hydrophila and mortalityrate was recorded for 14 days. RESULTS: Oral administration ofchitosan (0.5 and 1%) significantly enhanced NBT reductionactivity and resistance to A. hydrophila infection (p=0.012). Serumlysozyme and bactericidal activity, serum total protein andglobulin, WBC and leukocytes ratio showed no significant changeamong the groups (p>0.05). CONCLUSIONS: This study indicatesthat oral administration of shrimp shell chitosan may have a positiveeffect on some immune parameters and resistance against bacterialinfection in Cyprinus carpio.

BACKGROUND:Herbal methionine can be compared relative toDl-methionine with evaluation of bioavailability of this source ofmethionine. OBJECTIVES: An experiment was carried out todetermine the relative bioefficacy of herbal methionine (H-Met)®relative to DL-methionine (DL-Met) on performance criteria andimmunocompetence of Met sources in male broilers. Atotal of 160male broilers were fed a Met-deficient basal diet or the basal dietsupplemented with three or four concentrations of each Metsources. METHODS: Multiexponential and multilinear regressionswere used to determined bioavailability of herbal methionine (HMet)®relative to DL-Met on performance and immunocompetenceof broilers. RESULTS: Body weight gain and feed intake of thebroilers fed H-Met or DL Met improved in the experiment,regardless of Met sources, relative to those broilers that were fed thebasal diet. Immunocompetence of broilers were not significant at 28day of age (p>0.05), whereas the broilers were significantlyaffected by the additional levels of Met sources at 42 day of age.CONCLUSIONS: The bioefficacy estimates for H-Met® relative toDL-Met on a product basis were 55% for weight gain, 71% for feedintake, 78% for feed conversion ratio, 70% for dilution 1-choloro 2-3-dinitrobenzene (DNCB), 67% for sheep red blood cell (SRBC),and 68% for phytohemagglutinine (PHA-P). The relativeeffectiveness of H-Met® compared to that of DL-Met is 68% onaverage across performance criteria and all immune criteria tested.H-Met®can be supplemented as a new and natural source of Met forthe poultry industry.