Veterinary Research Forum

Abstract Among global concerns about antibiotic resistance, it is necessary to identify food-safe alternatives to enhance production. This study aimed to evaluate the impact of mannan oligosaccharides (MOS) inclusion to replace antibiotic growth promoters (AGP) in the diets of ISA Brown laying hens aged between 23 and 31 weeks. Two hundred forty hens were grouped into five treatments: Control, AGP (130 ppm of enramycin 8.00%), and 100, 200, and 400 ppm of MOS. Each treatment had 16 experimental units (each unit with n = 3) in a randomized block experimental design. Productive data (egg production %, feed intake, egg weight), egg quality variables (albumin height, yolk weight, albumin, yolk %, weight eggshell, eggshell %, equator thickness, width-pole thickness, and Haugh units), organ weights (ovary, liver, and cecum) and jejunal histomorphometry were analyzed. The egg production was not affected by the substitution of AGP by MOS. Furthermore, MOS supplementation resulted in significantly increased feed intake, larger egg weight, higher yolk weight and higher body and ovarium weight compared to the AGP group. Besides, MOS supplementation at 400 ppm demonstrated significant improvements in jejunal villus morphology indicating enhanced intestinal health. These findings highlighted the potential of MOS as an alternative to AGP, offering benefits such as improved feed intake, egg quality and intestinal health in laying hens at 400 ppm.

Abstract Resistance to the knockdown effect of pyrethroid insecticides occurs due to mutations at target sites of pyrethroids, meaning the voltage-gated sodium channels gene (VGSC) in the membrane of the neurons. In fleas, this mutation occurs at two sites in the sodium channel in neurons: one is the replacement of leucine with phenylalanine (L1014F) and the other is the replacement of threonine with valine (T929V). In this study, 81 Pulex irritans and 47 Ctenocephalides canis fleas were collected from five provinces in the west and northwest of Iran. Adult fleas were exposed to cypermethrin 0.75%, and the mortality rate was calculated after 1 and 8 hr, and the mutation sites in the VGSC gene were investigated. The lethality of cypermethrin 0.75% for P. irritans was 40.00 - 57.14% after 1 hr and 60.00 - 73.91% after 8 hr. The lethality of this dose for C. canis after 1 and 8 hr of exposure was 33.33 - 41.17% and 66.66 - 80.33%, respectively. The VGSC sequence analysis indicated two mutation sites in the resistant and one mutation site in the susceptible fleas. The VGSC sequence analysis of susceptible P. irritans showed that 5.50% of them were homozygous susceptible and 94.45% were hetero-zygous susceptible. Susceptible C. canis were 5.26% homozygous and 94.73% heterozygous susceptible. All the resistant fleas were homozygous. The development of pyrethroid resistance and high-frequency L1014F mutation in fleas suggest that pyrethroids are likely to be ineffective in controlling fleas. Therefore, monitoring pyrethroid resistance and its underlying mechanisms are necessary for controlling fleas and finding new alternative control methods.

Abstract The present study was aimed to assess the bedbugs susceptibility to pyrethroid insecticides using molecular analysis. With the aid of pest control companies, adult bedbugs were collected from various places such as hotels, residential houses, and industrial buildings in seven cities highly crowded with domestic and foreign tourists in Iran from May 2016 to August 2017. Bedbugs were colonized in the laboratory to evaluate their resistance to pyrethroid using insecticide resistance bioassay. Genomic DNA was extracted from susceptible and resistant bedbugs. At first, specie specific primers targeting cytochrome oxidase subunit I (COI) gene was performed to confirm Cimex hemipterus species. Then, kdr-like gene was examined for point mutation using PCR and nucleotide sequencing. Bioassay showed that 11 out of 35 examined bedbugs were resistant to pyrethroids (31.43%; 95.00% confidence interval: 29.48-33.08%). The DNA sequencing showed that all examined bedbugs collected from Tehran province had homozygous V419L kdr-like gene mutations. The level of pyrethroid resistance found in the collected bugs from Tehran province indicated that this phenomenon has already been prevailed in the site and prompts the need to reevaluate the large use of pyrethroids to control the bedbugs.