Duilio Majolini

Effect of decreasing dietary protein level and replacing starch with soluble fibre on digestive physiology and performance of growing rabbits.

At weaning (33 days of age), 246 hybrid rabbits (782 ± 53 g live weight) were divided into six experimental groups and fed ad libitum six iso-ADF diets formulated according to a bifactorial arrangement with two protein levels (152 and 162 g/kg) and three soluble fibre-to-starch ratios (0.2, 0.6 and 1.5), the latter obtained by replacing starch (from 209 to 91 g/kg) with soluble fibre (from 48 to 136 g/kg). The trial lasted for 42 days until slaughter. The rabbits that were fed the diet with the highest protein level and the lowest soluble fibre-to-starch ratio showed the highest mortality rate (17.1% v. 1.7% on average; P < 0.001) and sanitary risk (mortality + morbidity: 20.0% v. 8.1%; P = 0.04) compared with the rabbits fed the other diets. With increasing dietary crude protein level, the digestibility of dry matter (DM; 0.615 to 0.626) and gross energy (0.620 to 0.630) as well as aNDF (without sodium sulphite; 0.298 to 0.323) and hemicelluloses (0.417 to 0.461) significantly (0.001 < P < 0.10) improved. Moreover, total volatile fatty acids (VFAs) in the caecal content increased (59.0 to 68.4 mmol/l; P = 0.01) and ileum crypt depth tended to reduce (P = 0.07). Neither growth performance nor slaughter results were affected by the protein level. When increasing soluble fibre-to-starch ratio, the digestibility of DM and gross energy did not change, whereas the digestibility of aNDF (0.264 to 0.352), ADF (0.167 to 0.267) and hemicelluloses (0.400 to 0.470) linearly increased (P < 0.001). At caecum, N-ammonia tended to decrease linearly (P = 0.08), total VFA concentration (56.0 to 67.3 mmol/l) and acetate proportion (80.4 to 83.3 mmol/100 mmol VFA) linearly increased (P < 0.01), whereas butyrate and valerate proportions decreased (0.01 < P < 0.05). Growth performance was similar among groups, whereas at slaughter the proportion of the gastrointestinal tract linearly increased (177 to 184 g/kg; P < 0.01) without effect on dressing percentage, however. As soluble fibre-to-starch ratio increased, meat pH linearly decreased and lightness (L*), redness (a*) and yellowness (b*) colour indexes increased (0.01 < P < 0.05).

Housing of growing rabbits in individual, bicellular and collective cages: fear level and behavioural patterns

During growth (27 to 75 days of age), a total of 384 rabbits were kept in 72 individual cages, 48 bicellular cages (2 rabbits/cage) and 24 collective cages (9 rabbits/cage). To evaluate the effects of the housing system on the fear level and behavioural patterns of rabbits at the two ages (39 to 45 days and 66 to 73 days), a tonic immobility test and an open-field test were conducted and their behaviour was video recorded. In the tonic immobility test, the number of attempts to induce immobility (1.38) was lower, and the duration of immobility (47.8 s) was higher (0.05 < P < 0.01) in the rabbits housed in individual cages than in those kept in bicellular (1.72 attempts and 25.0 s of immobility) and collective cages (1.99 attempts and 25.0 s of immobility). During the open-field test, the rabbits from individual and bicellular cages showed higher latency (38.8 and 40.3 v. 27.0 s), a lower number of total (73.3 and 81.7 v. 91.9) and central displacements (3.6 and 2.8 v. 5.4) and a shorter running time (11.8 and 13.6 s v. 17.7 s) and the time biting the pen (5.5 and 9.1 s v. 28.2 s) compared with the rabbits kept in collective cages (0.05 < P < 0.001). During the 24-h video recording, the rabbits in individual and bicellular cages spent less time allogrooming (0.34% and 0.19% v. 1.44%), moving (0.74% and 0.60% v. 1.32%) and running (0.08% and 0.03% v. 0.21%) than the rabbits in the collective cages (0.01 < P < 0.001). The lowest numbers of alerts and hops were observed in the rabbits kept in bicellular cages. With increasing age, a lower number of rabbits were sensitive to the immobility test and more rabbits entered the pen spontaneously during the open-field test (P < 0.001). In conclusion, the rabbits in individual cages exhibited the highest fear level and incomplete behavioural patterns; the rabbits housed in collective cages showed the lowest fear levels and had the possibility of expressing a wider range of behaviour; and the rabbits in bicellular cages exhibited an inconsistent pattern of fear in the tonic immobility and open-field tests. Probably, these rabbits were in a less stressful condition compared with animals in individual cages because social contacts were allowed, even if freedom of movement was more limited.

Near infrared reflectance spectroscopy (NIRS) characterization of European sea bass (Dicentrarchus labrax) from different rearing systems.

Abstract The present study aimed to predict by NIRS the proximate chemical composition and some carcass traits of sea bass coming from 11 farms with different rearing systems (extensive, intensive in land-based basins, sea cages) and located in northern (Friuli, Veneto), central (Tuscany) and southern (Puglia and Sicily) Italy. NIRS analysis of freeze dried sea bass fillets gave fairly good predictions of slaughter weight and fillet yield (R2cv=0.48-0.55), while results for carcass yield were poor. NIRS analysis was highly predictive for the condition factor (R2cv=0.790, SECV=0.09) and for water, ether extract and gross energy showing high correlations (R2cv>0.90) with NIR spectral information and high accuracy (SECV=0.67%, 0.46% and 0.38 kJ/g for water, ether extract and energy, respectively). Crude protein prediction showed lower performance, even if still good, compared to previous variables (R2cv=0.734, SECV=0.34). The score plot of principal component analysis showed intensively-reared sea bass separated from extensively reared fish.

PCBs contamination in farmed European sea bass from different Italian rearing systems

The chemical composition and the level of twelve PCB congeners (IUPAC Nos. 18, 28, 31, 44, 52, 101, 118, 138, 149, 153, 180 and 194) were determined in 133 specimens of European sea bass (Dicentrarchus labrax), collected from four Italian aquaculture facilities: extensive valley, semi-intensive ponds, intensive concrete tanks and sea-cages. Fish muscle composition varied based on the rearing system (P<0.001): moisture was higher and fat concentration was lower in fish from the extensive system in comparison to fish from intensive tanks; intermediate values were found in fish from semi-intensive ponds and sea-cages. Concentrations of the 12 measured PCBs (PCB(tot)) and of the seven indicator congeners (PCB(7)) (Nos. 28, 52, 101, 118, 138, 153 and 180), when expressed on fat weight, were lower in extensively-reared sea bass (112.0 and 74.6 ng g(-1) fat, respectively) with respect to sea bass from the other systems (average values: 179.7 and 123.2 ng g(-1) fat) (P<0.001). When the values were expressed on fresh muscle weight, PCB(tot) and PCB(7) were lower in extensively-reared sea bass (3.412 and 2.266 ng g(-1)fw), intermediate in fish from semi-intensive ponds (15.398 and 10.632) and sea cages (13.123 and 8.882), and higher in specimens from the intensive tanks (18.176 and 12.440) (P<0.001). PCB 153 was the most abundant in all of the rearing systems. Within farm, muscular fat content and slaughter weight were positively correlated (r=0.79). PCB(7) concentration expressed in ng g(-1) fat and in ng g(-1) fw was positively correlated with both fish slaughter weight (r=0.71 and 0.73) and muscular fat concentration (r=0.86 and 0.96).

Housing of growing rabbits in individual, bicellular and collective cages: growth performance, carcass traits and meat quality

During growth (from 27 to 75 days of age), 384 rabbits were kept in different types of wire-net cages: 72 individual cages (72 rabbits; 10 animals/m2), 48 bicellular cages (96 rabbits; 2 rabbits/cage; 18 animals/m2) and 24 collective cages (216 rabbits; 9 rabbits/cage; 18 animals/m2). The rabbits housed in individual cages showed higher daily weight gain both during the fattening period (from 52 to 75 days of age) and during the whole period of growth (43.0 v. 41.8 and 41.5 g/day; P < 0.05), and they had a higher final live weight at 75 days of age (2678 v. 2619 and 2602 g; P < 0.05) compared with the rabbits in the bicellular and collective cages, respectively. Rabbits in individual cages ingested more feed (133 v. 127 and 126 g/day; P < 0.01), but the feed conversion did not differ significantly among rabbits housed in the three types of cages. At slaughter, the carcass traits and meat quality were weakly affected by the housing system. The transport losses were higher in rabbits kept in individual and bicellular cages compared with those reared in collective cages (3.1% and 2.9% v. 2.2%; P < 0.01). In rabbits kept in individual cages, the hind leg muscle to bone ratio was higher (6.35 v. 6.19 and 5.91; P < 0.05) compared with the bicellular and collective cages, respectively. The pH and colour of the longissimus lumborum did not change with the housing system, while the b* index of the biceps femoris was lower (3.04 and 3.32 v. 4.26; P < 0.001) in the rabbits kept in individual and bicellular cages, respectively, than in those kept in collective cages. In conclusion, the rabbits housed in individual cages showed higher daily growth than rabbits kept in bicellular or collective cages, but they had a similar feed conversion and carcass quality. Differently, neither in vivo performance nor slaughter results differed among the rabbits kept in bicellular cages or in collective cages. The meat colour may be affected by the housing system, but to an extent that is hardly perceivable by the final consumer.

Replacing starch with digestible fibre in growing rabbit feeding

Abstract To evaluate the effect of replacing dietary starch with digestible fibre (DF=pectin and hemicelluloses) on health status, digestive physiology, growth performance, and carcass traits, 250 hybrid rabbits weaned at 27 d were fed until slaughter (76 d) five diets with increasing DF to starch ratio (1.0 to 1.9; DF 18.9 to 22.2%; starch 19.6 to 11.5%). The digestibility of dry matter (64.7, 65.2, 66.8, 67.5 and 67.6%) and NDF (27.9, 32.2, 35.0, 40.2 and 41.5%) increased (probability of linear component of variance, L<0.001) with increasing DF to starch ratio. Final live weight and daily growth tended to decrease (L=0.06), feed intake significantly lowered (130 to 122 g/d, L=0.01) and feed conversion ratio improved (2.72 to 2.68; L<0.01). Health status, caecal fermentation and ileal mucosa traits of rabbits did not change. The feeding strategy failed in controlling the diffusion of epizootic rabbit enteropathy.

Evolution of European sea bass (Dicentrarchus labrax)freshness during storage

Abstract The study aimed to assess freshness evolution in 90 European sea bass (Dicentrarchus labrax) analyzed 2h after catch (day 0) and after 1, 2, 4, 6, and 8 days of storage at 2°C. Sea bass weighted 308±37g with average carcass yield of 89.8% and fillet yield of 48.8% slaughter weight. During storage skin colour indexes linearly changed (L<0.01) showing higher L* and lower a* and b* values. The eye liquor pH increased with storage, with both significant linear and quadratic components of variance. Fillet hardness increased from day 0 to day 4 and then decreased on day 8 (quadratic component of variance <0.01). Sensory freshness assessed by Quality Index Method showed a quadratic evolution and high correlation (R2=0.95) with days of storage.

Poly-chlorinated biphenyls (PCB) in European sea bass from different rearing systems

Abstract The chemical composition and the level of seven indicator congeners of PCB (BZ/IUPAC no. 28, 52, 101, 118, 138, 153, and 180) were determined in 133 specimens of farm-raised European sea bass (Dicentrarchus labrax). The fish were caught from different aquaculture rearing systems: extensive fish valley, semi-intensive ponds, sea-cages, and intensive concrete tanks. Fresh fillet chemical composition differed among the rearing systems (fat: 2.9, 7.5, 7.1, and 9.4%; P<0.001). Total concentrations of indicator congeners were below the EU limit (200ng/g fat) for meat, poultry and eggs, being the lowest in extensively-reared sea bass (75ng/g fat), intermediate in sea bass from semi-intensive ponds (119) and sea cages (116), and the highest in intensively-reared fish (133) (P<0.001). Similarly, PCB concentrations in fresh fillets were 2,438, 10,116, 8,491, and 12,952pg/g in the four systems (P<0.001). The congener 153 was the most represented in all rearing systems. TEQ concentrations for the dioxin-like congener no. 118 were 50 to 200 times lower than the maximum admitted value. Total concentration of indicator congeners of PCB was poorly correlated with fish slaughter weight (R2=0.17), while highly correlated with fat concentration of fish (R2=0.75).

Digestible fibre to starch ratio and protein level in diets for growing rabbits

Abstract To evaluate the effect of digestible fibre (DF) to starch ratio (0.8, 1.5, and 2.8) and protein level (15% and 16%) on health status, digestive physiology, growth performance, and carcass traits, 246 rabbits weaned at 33 d were fed until slaughter (75 d) six diets formulated according to a bi-factorial arrangement (3 DF to starch ratios by 2 protein levels). Growth performance and carcass quality at slaughter were not affected by treatments. Increasing DF to starch ratio did not modify dry matter digestibility (62.0% on average), while increased (P<0.001) DF digestibility (52.3 to 68.1%), stimulated caecal fermentation (total VFA: 56.0 vs 67.8 and 67.2 mmol/l; P=0.02) and changed VFA molar proportions. Increasing dietary protein increased digestibility of dry matter (P=0.02), crude protein (P<0.001) and digestible fibre (P<0.001) and increased caecal VFA production (P<0.01). The highest mortality (17.1% vs 1.5% average mortality of the other groups, P<0.001) was found in rabbits fed the diet with the lowest DF to starch ratio and the highest protein level.