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Black soldier fly (Hermetia illucens) larvae (BSFL) are rich in protein and have the potential to be used in animal feed. The aim of the present study was to determine the immunoprophylactic effect of BSFL against Salmonella Gallinarum in broiler chicks as an alternative feed additive. Results showed that BSFL improved body weight gain and increased frequency of CD4+ T lymphocyte, serum lysozyme activity, and spleen lymphocyte proliferation. Moreover, BSFL reinforced bacterial clearance and increased survivability of broiler chicks against S. Gallinarum. These data suggested that BSFL has prophylactic properties with stimulating non-specific immune responses, as well as reduced bacterial burden against S. Gallinarum.

In the swine industry, antibiotics or chemical therapeutics have been traditionally used as growth promoters to improve growth performance and prevent subclinical disease infection [15]. However, indiscriminate use of antibiotics has increased, and the spread of antibiotic-resistant pathogens as well as public concern with regard to their cross-transfer to humans through the consumption of pork that contains antibiotic resistance [4]. As a consequence, there is considerable attention on the development of alternative antibiotics that can be used for preventive feeding in pig nutrition and do not endanger the environment with their residues [19]. Naturally acquired compounds have been recently highlighted as promising alternative antimicrobial agents that could strengthen defense mechanisms and promote resistance to microbial infection by enhancing nonspecific systemic immunity [4, 10]. Salmonella enterica serovar Typhimurium (S. Typhimurium) is a frequently isolated Salmonella serotype in pigs and a well-known public health risk in commercial Salmonella-infected pork products [5]. The clinical signs of S. Typhimurium infection in pigs are increased body temperature accompanied by diarrhea and enterocolitis [26]. After recovering from the illness, the pigs are often stunted and grow slowly or remain as asymptomatic carriers in which the bacteria can persist without triggering any clinical signs [1, 3]. Therefore, Salmonella infection has economic concerns in swine production systems and negative implications in human public health [7]. Hence, limiting Salmonella infection in pigs could improve livestock production and human food safety [12]. Biotite and bentonite, which are silicate minerals, were originally used in various industrial applications based on their properties as catalysts, ion exchangers and absorbents [6, 18, 23]. Our previous studies have shown that dietary supplementation with biotite promotes the expression of several cytokines, such as interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), and promotes concanavalin A (T-cell mitogen)-induced lymphocyte proliferation in pigs [11, 13]. Biotite also shows antiviral activity against several viral agents, such as porcine circovirus, porcine reproductive and respiratory syndrome virus, and bovine herpesvirus type 1 [8, 11]. Furthermore, bentonite has several beneficial biological effects that are associated with its adjuvant-like action with several antibacterial agents. Bugla-Ploskonska et al. [2] reported that a bentonite and lysozyme therapy efficiently killed Salmonella enterica spp. and Salmonella bongori spp. Bentonite also shows an enhanced bactericidal effect against Escherichia coli when combined with metal or metal ion nanoparticles, such as silver (Ag), zinc oxide (ZnO), titanium oxide (TiO2), tungsten trioxide (WO3), tin dioxide (SnO2), cupric oxide (CuO) and magnesium oxide (MgO) [14, 17, 22]. These collective observations suggest that biotite combined with bentonite could be an alternative to antibiotics as a feed additive. Therefore, we investigated the bacterial clearance effect of biotite and bentonite mixture (BBM) on experimental infection with S. Typhimurium from the perspective of fecal shedding and the patterns of Salmonella distribution in disease-relevant tissues (cecum, colon and mesenteric lymph nodes (MLN)). We also examined several immune responses under normal and challenged conditions in the present study.

Antibiotics continue to be used as growth promoters in the poultry industry. Honeybee (Apis melifera) venom (HBV) possesses a number of beneficial biological activities, particularly for regulating the immune system. The aim of the present study was to evaluate the immunoprophylactic effects of HBV against Salmonella Gallinarum in broiler chicks as an initial step towards developing eco-friendly alternatives to reduce antibiotic use. HBV was administered using a spray technique. HBV improved body weight gain, particularly in the presence of infection. Moreover, HBV enhanced antibody production activity against formalin-killed S. Gallinarum. The CD4(+):CD8(+) T lymphocyte ratio, relative mRNA expression levels of interleukin-18 and interferon-γ, and serum lysozyme activity also increased following HBV administration before the infection period as well as during infection. HBV reinforced bacterial clearance and increased survivability against S. Gallinarum. Corresponding pathological analyses demonstrated that the HBV-sprayed group displayed mild and less severe abnormal changes compared with those in the control group. It was presumed that the prophylactic effects of HBV against S. Gallinarum were associated with its non-specific immune response stimulating activity. Thus, HBV may provide an alternative to reduce antibiotic use in the poultry industry.

It has been suggested that drinking oxygenated water may improve oxygen availability, which may increase vitality and improving immune activity. The present study evaluated the immune enhancing effects of oxygenated drinking water in broiler chicks and demonstrated the protective efficacy of oxygenated drinking water against Salmonella Gallinarum in experimentally infected broiler chicks. Continuous drinking of oxygenated water markedly increased serum lysozyme activity, peripheral blood mononuclear cell proliferation and the CD4(+)/CD8(+) splenocyte ratio in broiler chicks. In the chicks experimentally infected with S. Gallinarum, oxygenated drinking water alleviated symptoms and increased survival. These findings suggest that oxygenated drinking water enhances immune activity in broiler chicks, and increases survivability against S. Gallinarum in experimentally infected broiler chicks.

It has been considered that drinking oxygenated water improves oxygen availability, which may increase vitality and improve immune functions. The present study evaluated the effects of oxygenated drinking water on immune function in pigs. Continuous drink- ing of oxygenated water markedly increased peripheral blood mononuclear cell proliferation, interleukin-1β expression level and the CD4 + :CD8 + cell ratio in pigs. During Salmonella Typhimurium infection, total leukocytes and relative cytokines expression levels were significantly increased in pigs consuming oxygenated water compared with pigs consuming tap water. These findings suggest that oxygen- ated drinking water enhances immune activity in pigs and increases immune responses of pigs during S. Typhimurium Infection.

Although winter dysentery (WD) has been suspected to occur frequently in Korea, to date the exact epidemiology of WD has remained unknown. Therefore, we investigated the causative agents of WD by using electron microscopy, ELISA, RT-PCR, and nested PCR from 97 fecal samples of 32 WD-affected herds collected from 8 provinces during 2002-2004. The bovine coronavirus (BoCV) was consistently detected in all herds with WD. Of other pathogens, only coccidian oocyts were inconsistently but concurrently detected with BoCV. Ten isolates were identified as BoCV by immune electron microscope, immunofluorescent test and ELISA with antiserum to BoCV, and RT-PCR. From these results, it is concluded that WD caused by BoCV occurred in relatively high frequency and was widespread in Korea. The results provide important epidemiological data for the control and establishment of a surveillance system for WD in Korea.