Influence of diet on proximate composition and fatty acid profile in common carp (Cyprinus carpio)

Effect of nutritionally complete feed with different fatty acid profile on the fatty acid composition of common carp fillet

Hungarian pond fish production is based on grains, but in the last few years, new ideas and efforts have appeared to intensify carp production technology. The basic objective was to change grain-based feeding to nutritionally complete feeds, which ensure rapid growth and more efficient feed conversion rates. This study aimed to utilise empty ponds during the summer period for carp production. Thus, there is no need for fish producers to catch fish in large ponds at the operating water level to satisfy smaller market demands appearing during the summer.

The other aim was to compare the meat quality of fish raised on traditional and nutritionally complete feed until market size in the last year of production. Fatty acid profile and the levels of saturated, monounsaturated, and polyunsaturated fatty acids in fish fillets were specified, and their ratios were analysed. The result showed that nutritionally complete feed with different fatty acid composition affects the fatty acid composition of carp fillet during the rearing period. Quality of the fillet of carp fed with higher unsaturated fatty acid content became more favourable to the consumers due to health promoting effect of polyunsaturated fatty acids.

Characterisation of changes in physicochemical, textural and microbiological properties of Njeguška sausage during ripening

The purpose of this paper was to investigate effect of ripening time on physicochemical, textural and microbiological properties of Njeguška (dry fermented sausage) during ripening and to conduct sensory and free fatty acid characterization of final product. Ripening time significantly (p < 0.05) affected all physicochemical parameters. Moisture content dropped below national regulation limit (35%) after 12 days, which indicates that production process could be shortened for 4 days. Total weight loss was 36.34%. Due to its final pH (5.54), Njeguška can be classified as low-acid sausage which microbial safety mostly relies on its low water activity (< 0.80). Final TBARS value was 0.27 mg MDA/kg. Levels of tyramine (36.9 mg/kg) and putrescine (16.7 mg/kg) were the highest among all biogenic amines while levels of remaining amines were under 5 mg/kg. Hardness, gumminess and chewiness significantly (p < 0.05) increased during processing to reach final values of 65.59 N, 33.60 N and 19.12 N, respectively. Ripening time had significant effect on color (L^*, a^* and b^*) of surface, meat and fat parts which were all measured separately. Total viable count, lactic acid bacteria and Micrococcaceae counts increased from 5.11 log cfu/g, 3.90 log cfu/g and 2.41 log cfu/g to 7.96 log cfu/g, 7.04 log cfu/g and 4.86 log cfu/g, respectively. Results of sensory characterization showed high scores for smoky flavor, consistency, fattiness, fat/meat cohesiveness and saltiness while lactic acid odor and overall acidity were rated low.

Growth performance and immune status in common carp Cyprinus carpio as affected by plant oil-based diets complemented with β-glucan

Omnivorous fish species such as the common carp (Cyprinus carpio) are able to biosynthesise long chain polyunsaturated fatty acids (LC-PUFAs) from plant oil PUFA precursors, but the influence of the amount and quality of the LC-PUFAs biosynthesised from these oils on the immunocompetence status of the fish has received little attention. This study aims to evaluate whether the conversion of PUFA by carp induces a sufficient biosynthesis of LC-PUFA to maintain a good immunocompetence status in this species. Six iso-nitrogenous (crude protein = 39.1%) and iso-lipidic (crude lipids = 10%) diets containing three different lipid sources (cod liver oil (CLO) as fish oil; linseed oil (LO) and sunflower oil (SFO) as plant oils) were formulated with or without β-glucan supplementation at 0.25 g/kg diet. Juvenile carp (16.3 ± 0.6 g initial body weight) were fed a daily ration of 4% body weight for 9 weeks and then infected at day 64 with the bacteria Aeromonas hydrophyla. No significant differences in survival rate, final body weight, specific growth rate and feed conversion rate were observed between diets. After bacterial infection, mortality rate did not differ between fish fed CLO and plant oil-based diets, indicating that the latter oils did not affect the overall immunocompetence status of common carp. Plant oil-based diets did not alter lysozyme activity in healthy and infected fish. No negative effects of plant oils on complement activity (ACH50) were observed in healthy fish, even if both plant oil-based diets induced a decrease in stimulated fish two days after infection. Furthermore, the levels of various immune genes (nk, lys, il-8, pla, pge, alox) were not affected by plant oil-based diets. The expression of pla and pge genes were higher in SFO-fed fish than in CLO ones, indicating that this plant oil rich in linoleic acid (LA) better stimulated the eicosanoid metabolism process than fish oil. In response to β-glucan supplementation, some innate immune functions seemed differentially affected by plant oil-based diets. LO and SFO induced substantial LC-PUFA production, even if fish fed CLO displayed the highest EPA and DHA levels in tissues. SFO rich in LA induced the highest ARA levels in fish muscle while LO rich in α-linolenic acid (ALA) sustained higher EPA production than SFO. A significantly higher fads-6a expression level was observed in SFO fish than in LO ones, but this was not observed for elovl5 expression. In conclusion, the results show that common carp fed plant oil-based diets are able to produce substantial amounts of LC-PUFA for sustaining growth rate, immune status and disease resistance similar to fish fed a fish oil-based diet. The differences in the production capacity of LC-PUFAs by the two plant oil-based diets were associated to a differential activation of some immune pathways, explaining how the use of these oils did not affect the overall immunocompetence of fish challenged with bacterial infection. Moreover, plant oil-based diets did not induce substantial negative effects on the immunomodulatory action of β-glucans, confirming that these oils are suitable for sustaining a good immunocompetence status in common carp.

The quality of carp (Cyprinus carpio L.) cultured in various Polish regions

BACKGROUND

Although environmental factors greatly affect the quality of carp meat, no regulations impose labelling the place of cultivation of freshwater fish. That is why the purpose of this study was to determine the quality of carp meat cultivated in several regions of Poland as well as to assess the necessity of implementing such regulations.

RESULTS

The influence of the cultivation region on colour, nutrition value, health safety and sensory quality of carp meat was assessed. The analysis included colour measurement, determination of fatty acid profile and sensory evaluation of carp muscle. Moreover, microbiological analysis of the fish surface was performed. The results show that the place of cultivation does not influence the lightness (L*) of fillet, but has an impact on other colour parameters (a*, b*). The microbiological quality of fish from all studied farms was satisfactory, since no pathogenic microorganisms were observed on the fish surface. The fatty acid profile was fairly varied (P < 0.01), depending on the place of cultivation.

CONCLUSION

Since final results seem ambiguous, further analyses of quality features of carp from various regions and cultures should be performed, before any recommendation for the necessity of labelling the place and method of cultivation should be suggested.