Veterinary Research Forum

Abstract The natural polymer poly-β-hydroxybutyrate (PHB) is converted to β-hydroxybutyric acid, which is similar to short-chain fatty acids, via microbial fermentation and host enzyme breakdown. This study investigated the impact of different PHB concentrations (Control, 1.00, 3.00, and 5.00% substitution) on growth performances and fish welfare in common carp fingerlings. After a 60-day trial, fish fed on diet containing 1.00% PHB exhibited significantly higher weight gain and improved feed conversion efficiency compared to the control group. Furthermore, analysis of enzymatic activity showed elevated levels of total protease and amylase in PHB-fed treatments compared to the control. Red blood cell counts, hemoglobin, and hematocrit levels remained unaffected and a significant increase in white blood cell count was observed in fish fed on diets containing 1.00 and 3.00% PHB compared to the control group. Furthermore, fish fed on diets containing 1.00 and 3.00% PHB demonstrated significantly higher total protein levels and lower glucose concentrations as well as reduced hepatic enzyme activities (aspartate aminotransferase and alanine aminotransferase) compared to both the control and 5.00% PHB groups. Assessment of antioxidant and immune parameters revealed significantly increased complement hemolytic activity and immunoglobulin M levels coupled with decreased malondialdehyde concentrations in the plasma of PHB-fed fish compared to the control group. In conclusion, dietary supplementation with PHB, especially at the 1.00% level, enhanced growth performance and improved nutritional and health indicators in the fingerlings. These findings suggested that PHB had the potential to be a valuable dietary additive for this species.

Abstract A 35-day study investigated the impact of carbon sources and carbon/nitrogen (C/N) ratios on the microbial community of biofloc. For this purpose, we utilized a combination of phospho-lipid fatty acids (PLFAs) profiles and DNA-based sequencing methods to investigate changes in the microbial community composition and structure. The experiment involved three carbon sources including Dextrin (DEX), corn starch (CS) and wheat bran (WB) at two C/N ratios (19 and 30). The results indicated that WB and CS were found to decrease nitrogen metabolite concentration while increasing total suspended solids and bacterial density compared to DEX. The treatments exhibited variations in microbial communities and the use of polymerase chain reaction/ denaturing gradient gel electrophoresis analysis revealed distinct dominant bacterial species linked to carbon sources and C/N ratios. Furthermore, the highest levels of bacteria and protozoa PLFAs biomarkers were observed in the C/N30 ratio and WB treatment while the ratio for poly-β-hydroxybutyrate/PLFAs and fungi biomarkers displayed a decrease. Also, by incorporating the results of PLFAs profile and conducting a principal component analysis, the treatments were categorized into distinct groups based on both the carbon source and C/N ratios. Overall, both methods yield consistent results. PLFAs offered additional insights into the microbial composition beyond bacterial structure while DNA-based analysis provided finer taxonomic resolution.