Background Intestinal inflammation is prevalent in chicken, which results in decreased growth performance and considerable economic losses. Accumulated findings established the close relationship between gut microbiota and chicken growth performance. However, whether gut microbiota impacts chicken growth performance by lessening intestinal inflammation remains elusive. Results Seven-weeks-old male and female chickens with the highest or lowest body weights were significantly different in breast and leg muscle indices and average cross-sectional area of muscle cells. 16S rRNA gene sequencing indicated Gram-positive bacteria, such as Lactobacilli, were the predominant species in high body weight chickens. Conversely, Gram-negative bacteria, such as Comamonas, Acinetobacter, Brucella, Escherichia-Shigella, Thermus, Undibacterium, and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium were significantly abundant in low body weight chickens. Serum lipopolysaccharide (LPS) level was significantly higher in low body weight chickens (101.58 ± 5.78 ng/mL) compared with high body weight chickens (85.12 ± 4.79 ng/mL). The expression of TLR4, NF-κB, MyD88, and related inflammatory cytokines in the jejunum was significantly upregulated in low body weight chickens, which led to the damage of gut barrier integrity. Furthermore, transferring fecal microbiota from adult chickens with high body weight into 1-day-old chicks reshaped the jejunal microbiota, mitigated inflammatory response, and improved chicken growth performance. Conclusions Our findings suggested that jejunal microbiota could affect chicken growth performance by mitigating intestinal inflammation.

It has been established that gut microbiota influences chicken growth performance and fat metabolism. However, whether gut microbiota affects chicken growth performance by regulating fat metabolism remains unclear. Therefore, seven-week-old chickens with high or low body weight were used in the present study. There were significant differences in body weight, breast and leg muscle indices, and cross-sectional area of muscle cells, suggesting different growth performance. The relative abundance of gut microbiota in the caecal contents at the genus level was compared by 16S rRNA gene sequencing. The results of LEfSe indicated that high body weight chickens contained Microbacterium and Sphingomonas more abundantly (P < 0.05). In contrast, low body weight chickens contained Slackia more abundantly (P < 0.05). The results of H & E, qPCR, IHC, WB and blood analysis suggested significantly different fat metabolism level in serum, liver, abdominal adipose, breast and leg muscles between high and low body weight chickens. Spearman correlation analysis revealed that fat metabolism positively correlated with the relative abundance of Microbacterium and Sphingomonas while negatively correlated with the abundance of Slackia. Furthermore, faecal microbiota transplantation was performed, which verified that transferring faecal microbiota from adult chickens with high body weight into oneday-old chickens improved growth performance and fat metabolism in liver by remodelling the gut microbiota. Overall, these results suggested that gut microbiota could affect chicken growth performance by regulating fat metabolism.

The effect of lemon oil (Citrus limon) on Sarcoptes scabiei var. cuniculi was evaluated in vitro and in vivo. The mite samples were collected from naturally infected rabbits. The lemon oil was prepared in six concentrations by dilution with distilled water (2.5, 5, 10, 20, 50, and 100 %). In vitro application was done in five replicates for each concentration in petri dishes in the laboratory. The treated mites were observed at 1, 12, and 24 h post application (PA) for lemon oil effect. In addition, oxidative stress profile was evaluated for the treated mite. Dependent on in vitro results, 20 % lemon oil was used in vivo trial. Twenty-four naturally infected rabbits were divided into three groups of eight: 20 % lemon oil, deltamethrin, and untreated control. The infected parts of rabbits were treated topically once a week for four successive weeks. In vitro application results showed that lemon oil 10 and 20 % diluted in water caused mortality to 100 % of mites after 24 h PA. The oxidative stress profile revealed that mites treated with 20 % lemon oil had significantly (P < 0.05) higher hydrogen peroxide and malondialdehyde when compared with mites treated with deltamethrin or distilled water. In vivo application of 20 % lemon oil on naturally infected rabbits showed complete recovery from clinical signs, absence of mite in microscopic examination from the second week of treatment. In addition, productive performance was significantly better than infected untreated group. Also, the treated tissue showed stoppage of scale formation and hair growth faster than deltamethrin-treated rabbits. Consequently, lemon oil has remarkable miticidal activity in vitro and in vivo applications.

This study was conducted to investigate the causes of mortality in young rabbits. A total of 110 V-Line breed female rabbits aged 5 m were used in this study. Rabbit kits were examined daily in pre- and postweaning stages to detect clinical disorders that caused death. The postmortem examination was carried out on dead kits. Furthermore, rabbits were examined for the probable bacteriological and parasitological causes of death. Fecal samples were collected from each dead kit and examined by standard microbiological procedures for bacterial pathogens and macroscopically and microscopically for the presence of endo- and ectoparasites. Throughout two breeding seasons, 2238 newborns were obtained, of which 1736 died, accounting for a 77.57% mortality rate. During preweaning (1st month of age) and postweaning (up to 3 months of age), 1501 (67.10%) and 235 (31.90%) deaths were recorded, respectively. A postweaning fecal examination revealed that 198 out of 229 (86.50%) were diarrheic rabbits due to Eimeria infection. Cittotaenia spp. eggs were detected in 4.37% of fecal samples, and mites (Sarcoptis scabiei) were present in 6.55%. E. coli was detected in 100% of examined animals during pre- and postweaning periods; however, Salmonella spp. were 97.22% and 43.67, respectively. Managemental risk factors were the main causes in preweaning mortality, including insufficient milk supply (37.37%), cannibalism (26.38%), mange infestation of a rabbit doe (22.20%), mastitis (4.30%), lack of doe care (5.00%), bronchopneumonia (2.13%), and enteritis (1.80%). However, risk factors in postweaning mortality included sudden death with general septicemia (13.80%), enteritis (9.63%), bronchopneumonia (5.43%), mange infestation (2.04%), and malnutrition (0.81%). In conclusion, the etiology of preweaning mortality in kits was related mainly to the doe, especially managemental risk factors. However, a combination of multiple pathogenic agents (parasites and bacteria) and managemental factors was reported in the postweaning stage. Careful attention must be paid to avoid these causes.

The Myostatin (MSTN), or Growth and Differentiation Factor 8 (GDF8), gene has been implicated in the double muscling phenomenon, in which a series of mutations render the gene inactive and unable to properly regulate muscle fibre deposition. Single nucleotide polymorphisms (SNPs) in the MSTN gene have been correlated to production traits, making it a candidate target gene to enhance livestock and fowl productivity. This study aimed to assess any association of three SNPs in the rabbit MSTN gene (c.713T>A in exon 2, c.747+34C>T in intron 2, and c.*194A>G in 3'-untranslated region) and their combinations, with carcass, production and reproductive traits. The investigated traits included individual body weight, daily body weight gain, carcass traits and reproductive traits. The 3 SNPs were screened using PCR-restriction fragment length polymorphism (RFLP)-based analysis and the effects of the different SNP genotypes and their combinations were estimated in a rabbit population. Additionally, additive and dominance effects were estimated for significant traits. The results found no significant association between the c.713 T>A SNP and all the examined traits. Allele T at the c.747+34C>T SNP was only significantly associated (P<0.05) with increased body weight at 12 wk of age. However, for the SNP residing in the 3' untranslated region (c.*194A>G), allele G was significantly associated (P<0.05) with increased body weight and high growth rate. Genotype GG at the c.*194A>G SNP also had positive effects on most carcass traits. The estimated additive genetic effect for the c.*194A>G SNP was significant (P<0.05) with most body weight, daily gain and carcass traits. No significant association was obtained between any MSTN SNPs and reproductive traits. In the combinations analysis, regardless of the genotypes of SNPs at c.713T>A and c.747+34C>T, GG at the c.*194A>G SNP correlated with highest values in body weight and daily weight gain. In conclusion, the 'G' allele at the c.*194A>G SNP had positive effects on growth and carcass traits and so could be used as a favourable allele in planning rabbit selection. Further population-wide studies are necessary to test the association of the c.*194A>G SNP with carcass traits. We also recommend evaluation of the potential effects of the c.*194A>G SNP on MSTN gene expression.