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We analyzed the meat composition of ten females and seven males of sexually mature European beavers (Castor fiber L.). Cutting yield, percentage of particular elements, and chemical composition of the meat were determined. On average, a beaver carcass constitutes 48.6% of beaver body mass and contains 62.8% of meat, 14.5% of fat and 22.4% of bones. The thigh was found to be the largest and most valuable element constituting 33.4% of carcass weight and containing 66.7% of meat. Beaver meat has a high concentration of protein (20.9-21.8% wet wt.) and minerals (1.27-1.31%). The fat was characterized by a high proportion of polyunsaturated fatty acids (48.0-53.1%).

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ABSTRACT:The aim of this research was to determine the slaughter yield, proximate composition, and flesh colour of cultivated and wild perch (Perca fluviatilis). The study material was composed of fish obtained from intense fattening on formulated feed (age 1+, mean body weight (BW 116 g)) and wild specimens caught in a lake (age 3+, BW 119 g). The biometric traits of the two groups of fish did not differ with regard to body weight, total length (Lt), body length (Lc), or condition coefficient (P > 0.01). The cultivated perch had both higher maximum body height (H) and relative body profile (Rp) (P ≤ 0.01). The cultivated perch has a significantly lower slaughter yield (P ≤ 0.01). This dependence stems from the heavier viscera, which included more perivisceral fat and larger liver. Cultivated perch had significantly higher values of the viscerosomatic (VSI; 12.0 vs. 6.4), hepatosomatic (HSI; 1.9 vs. 1.7), and perivisceral fat (IPF; 7.0 vs. 1.2) indices. The analysis of the proximate composition of fillets from wild and cultivated perch indicated that the ratios of protein, fat, water were significantly different (P ≤ 0.01). The higher content of dry matter in the cultivated perch was a result of higher fat and protein contents. The fillets of the two groups of perch differed with regard to the saturation of green and yellow pigment; the cultivated perch exhibited lower values of parameter a* and higher values of parameter b* (P ≤ 0.01).

The aim of the study was to determine the effect of diet on the fatty acids composition of cultured northern pike (Esox lucius) fillet (mean body weight, 620 g; age, 2.5 years; commercial feed) profiles when compared with wild pike caught in Lake Dgał Wielki in northern Poland (mean body weight, 570 g; age 3.5 years). Cultured pike fillets contained several times more fat (2.40%) compared with wild fish (0.19%, P < 0.01). The total relative quantity of saturated fatty acids (SFA; % of total fatty acids) and unsaturated fatty acids (USFA) in cultured and wild pike were similar. Monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) content differed in wild and cultured fish. Cultured pike contained nearly two times more MUFA (30.90% compared with 15.97%; P < 0.01) but less PUFA (42.04% compared with 58.33%; P < 0.01), n-3 PUFA (32.42% compared with 41.26%; P < 0.01), and n-6 PUFA (6.47% compared with 15.79%; P < 0.01). The largest differences were noted with regard to docosahexaenoic acid (DHA) and arachidonic acid (AA), the levels of which in cultured and wild pike were 18.93% vs 27.96% and 0.73% vs 8.60%, respectively (P < 0.01). Quality compositions of the commercial feed and the cultured pike fillets were identical.

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Juvenile tench (initial weight of about 57 g) were fed feed supplemented with fish oil (group FO), linseed oil (group LO), peanut oil (group PO), or rapeseed oil (group RO) containing 47% protein and 12% fat for 55 days. The inclusion of the tested oils was 50 g kg -1 (42% total crude lipids in diets). No significant differences were noted in the fish growth performance. The proximate composition of the whole fish bodies and the viscera (water, protein, fat, ash) was similar in all the dietary treatments (P [ 0.05). Differences were noted only with regard to the ash content of the fillets (P \ 0.05). The analysis of the fatty acids profiles of tench (whole fish) indicated there were significant differences in the total content of monoenoic and polyenoic (PUFA) acids. Significant differences were also noted with regard to n-3 PUFA and n-6 PUFA. Consequently, the ratio of n-3/n-6 acids ranged from 1.6 (group PO) to 2.08 (group LO; P \ 0.05). The feed applied was not confirmed to have had an impact on the fatty acids profile of the tench fillets. There was a statistically significant intergroup difference in the content of saturated fatty acids (SFA) in tench viscera. In the fish fed vegetable oils supplemented diets, the level of SFA was lower (P \ 0.05).