Impacts of poultry by-product meal substituting fishmeal on growth efficiency, body composition, liver, and intestine morphology of European sea bass, Dicentrarchus labrax.

A twelve week feeding experiment was conducted to evaluate the replacement of fishmeal (FM) with poultry by-product meal (PBM) in practical diets for European sea bass, Dicentrarchus labrax with an average initial weight of 0.89 g. Five isocaloric (5.1 kcal lipid g-1) and isonitrogenous (451 g protein kg-1) diets were formulated with PBM replacing FM at levels of 0% (control), 25%, 50%, 75%, and 100%. The experiment was carried out in 30-in. nylon mesh net cages (hapas). At the termination of the trial, growth performance including final body weight, weight gain, specific growth rate, and protein growth rate of diets containing up to 75% PBM were comparable to those of the control group, whereas the diet with 100% PBM resulted in a significantly lower values (p < 0.05). Feed utilization exhibited variation among the treatments (p < 0.05). Whole body composition also showed significant differences across the dietary treatments. Essential amino acid (EAA) contents specifically arginine (Arg), histidine (His), methionine (Met), and threonine (Thr) in the whole body of fish fed diets with up to 50% PBM replacement were not significantly different from those in the control group. Furthermore, the intestinal microvilli length, width and absorption area increased significantly (p < 0.05) with PBM replacement levels up to 50%. Histological analysis of the liver revealed mild vacuolation of hepatocytes in fish fed up to 50% PBM,while pre-pancreatic fatty degeneration of hepatocytes was observed in fish fed diets with 75% and 100% PBM. Therefore, this study demonstrates that PBM can replace up to 50% of FM in the diets of European sea bass without adverse effects on growth performance, body composition, or liver and intestine morphology.

Effects of exogenous bile acids (BAs) on growth, lipid profile, digestive enzymes, and immune responses of thinlip mullet, Liza ramada.

An eight-week trial was designed to explore the dietary effects of commercially purchased exogenous bile acids (BAs) on growth, whole-body composition, lipid profile, intestinal digestive enzymes, liver function enzymes, oxidative stress biomarkers, and serum immunity of thinlip mullet, Liza ramada. Four triplicate groups (10.50 ± 0.05 g) were fed four soybean meal (SBM)-based diets supplied with several BAs levels at 0 (control), 50, 130, or 350 mg/kg feed. Results indicated that the growth was significantly increased in groups fed BAs-based diets, especially at 130 mg/kg feed. The body composition analysis showed that feeding fish on diets supplied with BAs up to 130 mg/kg decreased moisture (%) alongside increased crude protein (%). However, the body composition of fish fed a diet with 350 mg BAs/kg had the lowest moisture (%) and the highest crude protein (%). Moreover, there were significant increases in the intestinal (protease, α-amylase, and lipase) enzyme activities in the groups supplied with BAs up to 130 mg BAs/kg. Liver function enzymes (aspartate aminotransferase and alanine aminotransferase enzyme activities) were significantly decreased in BAs-supplemented groups compared to those fed the BAs-free group. On the other hand, the control group had higher total cholesterol, triglycerides, and low-density lipoprotein alongside the lower high-density lipoprotein than BAs-supplemented groups, especially at 350 mg BAs/kg feed. BAs significantly decreased hepatic malondialdehyde concentrations and increased the activity of hepatic catalase, superoxide dismutase, and total antioxidant capacity compared with those reared on the control diet. Serum lysozyme, respiratory burst, and alternative complement activities were significantly increased in BAs-supplied groups, particularly in the group supplied with 130 mg BAs/kg compared to those fed on the control diet. Accordingly, our findings recommend that including 130 mg BAs/kg in an SBM-based diet enhanced the growth, digestive enzyme activities, and liver functions, alleviated oxidative stress, boosted serum immunity, and lowered lipid metabolites in thinlip mullet. These findings will be beneficial for improving the quality of feed prepared for feeding mullets and an effective alternative strategy to support mullet farming.

Growth performance, antioxidant activities, and immunological responses of hapa-reared thinlip mullet (Liza ramada) juveniles fed on diets supplemented with spirulina (Arthrospiraplatensis).

Spirulina (Arthrospira platensis) (SP) has been utilized for a long time as a valued feed supplement because of its proteinous content and other beneficial phytochemical compounds. Herein, we investigated the influences of SP-supplemented diets on growth, body somatic indices, digestive enzymes, hepatic antioxidant activities, and immunological responses of hapa-reared thinlip mullet (Liza ramada) juveniles. Fish were assigned in six triplicate groups and were fed for consecutive 60 days on the prepared experimental diets containing varying SP levels as 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 g/kg diet and defined as control (CNT or SP0), SP2, SP4, SP6, SP8, and SP10 groups, respectively. The results indicated that dietary SP supplementation linearly and quadratically improved the fish growth performance, and the highest growth indices were found in the SP8 group. However, dietary SP supplementation did not significantly alter feed conversion ratio (FCR), survival rate (%), hepato-somatic index, and viscera-somatic index among all experimental groups. Meanwhile, digestive enzymes (lipase, α-amylase, and proteases) in the mid-intestine were also linearly and quadratically increased in all SP-fed groups, and their uppermost values were noted in the SP8 group. Hepatic antioxidants such as superoxide dismutase, catalase, and total antioxidant capacity in SP-supplemented groups were significantly elevated than the CNT group. Conversely, hepatic malondialdehyde contents were decreased significantly along with increasing dietary SP-supplementation levels. The immunological parameters such as lysozyme, respiratory burst, and alternative complement activities were significantly elevated in SP-fed groups than in the CNT group. These findings evoked that feeding SP-supplemented diets (especially at 8.0 g/kg diet) significantly promoted the growth, digestive enzymes, hepatic antioxidant status, and immunity of L. ramada juveniles.