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

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 af- fected 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 cae- cal 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

Alternative matrices for cortisol measurement in fish.

Plasma cortisol is the most commonly used indicator of stress in fish but, as the blood sampling procedure itself can be a source of stress, it would be helpful to measure cortisol using less invasive matrices. It is also necessary to find alternative matrices as stress indicators in dead fish in which blood sampling is impossible. In the present study, we investigated transport stress in three aquaculture species, European sea bass (Dicentrarchus labrax L.), common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum), by cortisol determination (radioimmunoassay) in plasma and other matrices (skin mucus, gut content, lateral muscle and caudal fin). Cortisol significantly increased after transport in all species and matrices, except in the sea bass gut content, where it remained unchanged. The three species responded to transport stress by producing different cortisol levels. In conclusion, the significant correlation found between plasma cortisol and most of the other matrices opens up the possibility of using them to evaluate stress in fish: mucus sampling is a less invasive method than blood sampling, and in addition to muscle and fin sampling, it can be used in postmortem fish

CARATTERIZZAZIONE QUALITATIVA, EVOLUZIONE DELLA FRESCHEZZA E IDENTIFICAZIONE DI SPIGOLE (Dicentrarchus labrax L.) PROVENIENTI DA DIFFERENTI SISTEMI DI ALLEVAMENTO

Qualitative characterization, freshness evolution and identification of European sea bass (Dicentrarchus labrax L.) from different rearing systems This PhD thesis is divided into four main sections: introduction, objectives, material and methods, results and discussion and is concluded by general considerations and reference list. Introduction In this section, world and national statistics on wild captures and cultivated fish production are reported, with detailed information on European sea bass production in the Mediterranean basin. Morphological traits and ecological needs of sea bass are described, as well as the equipments and techniques for artificial reproduction and fattening. The second part of the work is dedicated to outline the state of art on the specific items that have been investigated here, that are the characterization of biometric traits, chemical composition and dietetic value of fish and sea bass, the food safety, with the problem of PCB and heavy metal contamination, the assessment of freshness evolution and, lastly, the possible utilization of NIR spectroscopy for the characterization and origin identification of fish and fish product. European sea bass, together with sea bream, is the main fish species reared in Italy after trout. The great competition existing among producing Countries of the Mediterranean area (especially Turkey, Greece, Spain, Croatia) and the relative consequences on market prices require the national product to be characterized for quality and food safety at origin. Even if with some differences among Countries, European consumers give increasing attention to food safety and are especially worried about the possible presence of inorganic and organic persistent pollutants in fish products. On one hand wild and cultivated fish have recognized higher nutritional quality in comparison with terrestrial animals, thanks to the high concentration in poly-unsaturated fatty acids of the ω-3 series, on the other hand fish products are more sensible to accumulate contaminants which concentrate along the natural trophic chain or may be present in commercial feeds. The control of heavy metals and polychlorinated biphenyl (PCB) concentration has a key role, because these pollutants are concentrated in the meat of carnivorous animals at the top of the trophic chain and their presence, even if still debated, is associated to various metabolic, hormonal and reproductive diseases as well as the occurrence of cancers. In post-mortem, fish product quality is strictly correlated to the degree of freshness and storage condition. These characteristics may be evaluated by different means based on analytical determination of degradation metabolites, as well as on sensory methods based on standard EU methods (Reg. EC 2406/96) or more recently-developed schemes adapted to the different species and product category (Quality Index Method, QIM). Among innovative methodologies, Near Infrared Reflectance Spectroscopy (NIRS) may be successfully used for a full evaluation of fresh and stored fish products. Largely used to evaluate nutritional characteristics of livestock feedstuffs, characterize and identify the origin, and detect adulterations in a wide range of products, NIRS analysis has been successfully apply also to fish products to predict flesh composition of various species, besides identify their origin and evaluate their freshness. Objectives With the main aim of contributing to reinforce programs for global quality, food safety and sea bass promotion by means of a wide study about biometric, chemical, dietetic, sensorial and toxicological traits of fish of various commercial sizes and coming from farms with different productive systems as well as geographic locations along Italy, the present thesis developed the following specific objectives: Objective 1 - QUALITY. Characterization of morphological, chemical and nutritional traits of sea bass coming from Italian farms with different rearing systems. Objective 2 - POLLUTANTS. Determination of the presence and concentration of persistent environmental pollutants (PCB and heavy metals) in sea bass from Italian farms with different rearing systems. Objective 3 - FRESHNESS. Evaluation of freshness change in reared sea bass as affected by storage duration and productive system. Objective 4 - NIRS. Using NIRS analysis to characterize chemical and nutritional composition, to evaluate freshness and identify the origin of sea bass from different rearing systems. Material and Methods Sampling Four groups of sea bass were caught and analysed at different moments: Sampling no. 1: 133 sea bass from four farms with different rearing system (extensive valley, semi-intensive ponds, intensive tanks, intensive sea cages). Sampling no. 2: 170 sea bass of two commercial sizes (400-600 g and 700-1000 g) coming from 11 Italian farms and belonging to three rearing systems (extensive valley, intensive tanks, intensive sea cages). Where used and when possible, the commercial diet fed to sea bass during the last period of growth before caught was sampled. Sampling no. 3: 90 sea bass taken in a different moment from the same semi-intensive farm used for the sampling no. 1. Sampling no. 4: 90 sea bass from three farms with different rearing systems (extensive valley, intensive tanks, intensive sea cages) and already used for sampling no. 1 and 2. Sample preparation and analyses After caught and sacrificed in water and ice, sea bass were submitted to the following preparation and analyses: • sensorial evaluation of freshness by the standard EU scheme (Reg. EC 2406/96) and two QIM (Quality Index Method) schemes; • biometries and morphometric indexes: total length, standard length, maximum height and head length were measured and used to calculate the condition factor, relative profile, and cranial index; • skin colour (L*a*b*) at 3 dorsal and 2 ventral points by spectrophotometer; • texture profile analysis (TPA) of the whole fish by dynamometer; • eye pH; • gut and internal organs were removed and weighed: gut, liver, perivisceral fat, gonads; fillets with skin were separated from eviscerated carcass and weighed; hepatosomatic index, viscerosomatic index, mesenteric fat index, gonadic index, carcass and fillet percentages were calculated; • fillet colour (L*a*b*) at 3 dorsal and 2 ventral points by spectrophotometer • fillet pH at three dorsal points; • fillet texture profile analysis (TPA); • NIRS analysis of fresh minced filled without skin by monocromator spectrometer within 1100 and 2500 nm wavelengths; • lipid extraction and fatty acid profile of muscular fat by gas-chromatography; • total volatile basic nitrogen (TVBN) in fresh minced fillet; • freeze-drying of fillets; • NIRS analysis of freeze-dried fillets as for fresh fillets; • chemical characteristics (water, ether extract, protein, ash) and energy content of freeze-dried fillets; • heavy metals concentration in fillets and diets by ICP-MS (Inductively Coupled Plasma Mass Spectrometry) after sample mineralization; • PCB concentration in fillets and diets. For sea bass of sampling no. 1, 12 congeners were determined representative of PCB contamination, among which the 7 indicator congeners (28, 52, 101, 118, 138, 153 e 180). On 18 pool of fillets and 7 diets of sampling no. 2, PCB were measured as concentration and sum of equivalent toxicity (TEQ) of the 12 dioxin-like PCB congeners. Data treatment and statistical analyses Objective 1 - Quality. Biometric data and morphometric indexes (samplings no. 2, 3, and 4) and analytical data (samplings no. 1, 2, 3, and 4) were submitted to analysis of variance (ANOVA) by GLM procedure (SAS), considering as main variability factors the rearing system and fish size. Objective 2 - Pollutants. Data of heavy metals and PCB concentrations were submitted to analysis of variance considering the rearing system as main factor (samplings no. 1 and 2). For data of sampling no. 2, fish live weight at slaughter was included as covariate in the model. Besides, correlation coefficients and regressions were calculated between fish live weight and ether extract concentration; fish live weight and PCB concentration (ng/g fat); ether extract and PCB concentration (ng/g fat). Objective 3 - Freshness. Morphometric and analytical data were submitted to analysis of variance with storage time (samplings no. 3 and 4) and rearing system (sampling no. 4) as main factors. The results of sensory evaluation were analyzed by Proc UNIVARIATE (SAS). Data with normal distribution were submitted to Proc. GLM; data with non-normal distribution were analysed by non-parametric analysis of variance (Kruskal-Wallis and Mann-Whitney tests) with Proc. NPAR1WAY. Objective 4 - NIRS. Spectra were taken in reflectance, transformed in absorbance and derivatized (2, 20, 20). Calibrations to predict the chemical composition of fillets and some carcass characteristics were calculated by Partial Least Square Regression (PLSR) on derivatized spectra and validated by full cross-validation. Principal Component Analysis (PCA) and Soft Independent Modelling Class Analogy (SIMCA) were used to discriminate and classify samples according to origin (samplings no. 2 and 4) and storage time (samplings no. 3 and 4). Results Objective 1 - Quality The rearing system significantly affected morphologic, biometric and reologic traits, besides chemical composition of sea bass. In fish of sampling no. 2, the carcass percentage was significantly higher (P<0.05) in sea bass from extensive systems (87.7%) in comparison with those reared intensively in sea cages (85.9%) and similar to that of sea bass reared intensively in concrete tanks (87.0%). Fillet percentage was lower in extensively-reared sea bass compared to fish of the other systems (46.1 vs. 48.5%). The index of mesenteric fat was lower in sea bass reared in sea cages in comparison with those from extensive valleys or land intensive systems (2.21 vs. 3.40 and 4.24%; P<0.05). In sampling no. 4, differences among rearing systems were even accentuated. In both samplings, the intensity and saturation of red and yellow colour indexes were greater in sea bass from extensive rather than from land intensive system and, even more, than in those from sea cages (P<0.05). Further differences were evidenced in the TPA of whole fish (sampling no. 4), with the maximum force for the first compression significantly higher in sea bass from extensive and sea cages systems compared to those from land intensive systems (29.2 and 26.7 vs. 21.8 N; P<0.001). Fillet pH was higher (P=0.02) in fish from sea cages (6.42) than in those from extensive or land intensive systems (6.28 and 6.29). In all samplings (no. 1, 2), fillets from extensive farms had less muscular fat (P<0.01) compared to intensively-reared sea bass (in tanks, ponds or sea cages). Moreover, fillets from fish coming from intensive tanks were fatter that those from sea cages (P<0.05). Energy content of fillets increased with fat content, while water concentration decreased. The size of sea bass (small and large; sampling no. 2 on 11 farms distributed along Italy) affected significantly biometric traits, relative profile and cranial index, but to a limited extent in absolute value. Heavier sea bass showed higher condition factor and higher incidence of losses at evisceration (hepatosomatic index) (P0.05). The percentage of fillets was higher in large than in small fish (48.2 vs. 47.2%; P=0.05). The size of sea bass did not affect the skin colour indexes except for L* values in the dorsal side of fish, showing higher brightness in sea bass of small size (42.6 vs. 39.7; P<0.05). Fillet chemical composition was not significantly affected by the commercial size of sea bass. Sampling no. 3, with sea bass from only one farm with semi-intensive system, was used to obtain information on acidic profile of muscular fat. Saturated fatty acids were 26.5% of total fatty acids, with palmitic acid as the most represented. Monounsaturated fatty acids were 34.5%, with oleic acids reaching 50% of them. The content of polyunsaturated fatty acids (PUFA) was 34.4% on average, with a light prevalence of ω-3 PUFA (17.3%) on ω-6 PUFA (15.8%) series. Within ω-6 PUFA, the main acids was alpha-linoleic; within ω-3 PUFA, eicosapentaenoic and docoesaenoic acids were the most abundant. Objective 2 - Pollutants In sea bass of sampling no. 1, the rearing system significantly affected the total concentration of the 12 most abundant PCB (PCBtot) and the 7 PCB indicators (PCB7), which were less concentrated in extensively-reared sea bass (112.0 and 74.6 ng/g fat, respectively) in comparison with sea bass from the other rearing systems (on average 179.7 and 123.2 ng/g fat, respectively) (P<0.001). When concentrations were given on fresh muscle weight instead of on fat weight, PCBtot and PCB7 levels were lower in extensively-reared sea bass (3,412 and 2,266 ng/g fresh weight, respectively), intermediate in sea bass from semi-intensive ponds (15,398 and 10,632) and from sea cages (13,123 and 8,882), and higher in intensively-reared sea bass (18,176 and 12,440) (P<0.001). Within rearing system, ether extract concentration of the fillet and slaughter live weight were positively correlated (r=0.79). PCB7 concentration expressed on g fat was positively correlated with both sea bass slaughter weight (r=0.71) and fillet fat concentration (r=0.86). The correlation between fish slaughter weight and fillet fat concentration increased (r=0.73 and 0.96, respectively) when PCB7 was given on fresh weight basis. The correlation degree between PCB7 concentration on fresh weight and sea bass slaughter weight was affected by the rearing system, while the correlation between PCB7 and fat concentrations in fillets was not. The total content of the 12 dioxin-like PCB in diets obtained in the frame of sampling no. 2 (and fed to sea bass during the last period of growth) was higher in sea-cage farms G1 (29.35 ng/g fat) and G3 (15.80 ng/g fat) followed by the intensive farms I1 and I3 (12.72 and 12.62 ng/g fat, respectively), while very low contaminations were found in diets of the other farms. In fillets, depending on the rearing systems, only concentrations of PCB congeners no. 126 and 189 significantly changed, but the variations in PCB no. 126, low concentrated but very toxic, determine the major changes in fish toxicity equivalent (TEQ). The highest value of TEQ was in fact measured for PCB no. 126 in fillets of sea bass from extensive systems (19.7 pg/g fat; P=0.05) rather than in those from intensive systems (7.6 pg) or sea cages (11.0 pg). As a consequence, the sums of toxicity equivalents (ΣTEQ), expressed in g fat, significantly changed (P=0.05) according to the rearing system with the highest values in extensive farms compared to land or sea cage intensive systems (21.9 vs. 8.89 and 12.6 pg/g fat, respectively). When expressing data on fresh weight basis, however, ΣTEQ was not significantly different among rearing systems (from 0.72 to 0.83 pg/g fillet). The size of fish did not affect dioxin-like PCB concentrations and ΣTEQ, both when expressed on fat and on fresh weight. In sea bass of sampling no. 1, PCB7 concentration (75-131 ng/g fat) was always lower to the limit (200 ng/g fat) established in 1999 by the European Union Regulations for swine and poultry meat and derived products for human consumption. On 2006, the European legislation established for fish and fish products a maximum concentration of dioxins and furans equal to 4.0 pg TEQ/g fresh weight and the sum of dioxins, furans and dioxin-like PCB equal to 8.0 pg TEQ/g fresh weight. In fillets coming from sampling no. 2, also the highest dioxin-like PCB concentration found in an extensive farm (TEQ 45.3 pg/g fat equal to 0.735 pg/g fresh weight) was largely below law limits. As what concerns heavy metals, great differences were found in the metal concentrations in the feed sampled in the different farms: arsenic concentration was higher in farms G1 and I2 and lower in farms E3, I1, I3, G3 and G4. The concentration of the other metals was less variable among diets. None of the analysed samples contained mercury at a detectable level, while zinc and copper concentrations were rather abundant, likely because of the commercial diet supplementation. Rearing system significantly affected heavy metal concentration in flesh. When detectable, mercury concentration ranged from 0.023 to 0.152 mg/kg DM, with the highest values in extensively-reared sea bass, but always lower than the 0.5 mg/kg fresh weight established by the EU rules. Arsenic was found at high concentrations (12-15 mg/kg DM) in one of the extensive farms, while ranged from 1 to 3 mg/kg DM in most cases, and was even below 1 mg/kg DM in some farms. Copper concentration of extensively reared sea bass was lower than in fish from land and sea cage intensive systems (0.82 vs. 1.03 and 1.06 mg/kg fresh weight; P<0.01). Fillet lead concentration, even if not statistically different, was higher in sea bass from intensive systems (0.13 mg/kg fresh weight). In two out of the four intensive farms, this value (0.22 and 0.30 mg/kg fresh weight) was higher than the law limits, that is 0.20 mg/kg fresh weight. Also arsenic concentration was 3-4 fold higher in extensively-reared sea bass than in sea bass from land or sea cages intensive systems, even if with a low statistical significance (P=0.12). The size of fish did not affect heavy metal concentrations. Objective 3 - Freshness Freshness evolution was evaluated on sea bass of sampling no. 3, for which the effect of storage time was considered, and on Set n. 4 for which the effects of both storage time and rearing systems were evaluated. The sampling no. 3 consisted of 90 sea bass coming from a semi-intensive farm and stored in groups of 15 specimens during 0, 1, 2, 4, 6 and 8 days in boxes without ice and in a refrigerated room at 2°C. During storage, biometric and carcass traits little varied. At the sensorial evaluation, 8 days after slaughter, sea bass showed a still acceptable degree of freshness, even if some traits (shining, mucus presence, hardness for general aspect; gill odour and mucus) degraded quickly in comparison with other traits. Eye characteristics did not change and the loss of colour at abdomen was limited, while abdomen consistency and the odour of cloacae impaired to an intermediate degree. The regression between QIM scores from 0 to 8 days of storage was explained by a high coefficient of determination (R2=0.95), with a linear (increase with the time of storage) and quadratic evolution (reduction of the increase in value with the days of storage). Among rheological measurements, eye pH decreased from 7.25 at day 0 to 7.04 at day 4 to increase again at 7.48 after 8 days of storage (linear and quadratic component of variance, P<0.001), while fillet pH did not change. During storage, skin lightness linearly increased with days from 44.8 to 52.3, with the highest value after 2 days of storage; the red index moved from positive values around zero to minimum values tending to green; the reduction of b* index evidenced a corresponding reduction of yellow component (from 5.63 to 2.42) with a quadratic trend (Q=0.02). As what concerns fillet colour, lightness increased with storage length (L<0.001 and Q<0.01). The indexes a* and b* increased on day 1 and 2 and then decreased after 6-8 days of storage (L<0.01; Q<0.05). Fillet texture significantly changed: hardness increased from slaughter (4.86 N on day 0) to day 4 of storage (7.20 N), then decreased on days 6 and 8 (L<0.001; Q=0.02) according to the onset and resolution of rigor mortis. The value of elasticity linearly decreased (L=0.09), even if the lowest values were measured 1 and 2 days after slaughter (Q<0.01). As what regards the chemical composition, during storage, the total volatile basic nitrogen concentration increased (from 15.6 to 16.5 mg/100 g; L<0.001). When considering the fatty acid profile of sea bass fillet fat, the concentration of palmitic acid decreased linearly from 17.8 to 17.1% with increasing days of storage, while changes in stearic acid were limited in absolute value even if significant at a statistical level. The concentration of mono-unsaturated fatty acids did not change, while, among ω-6 polyunsaturated fatty acids (PUFA), the concentration of alpha-linoleic acid was higher after 8 days of storage. Arachidonic acid, present in small amounts, significantly decreased its concentration during storage. Among ω-3 PUFA, linolenic acid linearly increased (from 2.04 to 2.23%), while eicosapentaenoic and, expecially, docosahexaenoic acids significantly diminished with the days of storage. The analyses of further 90 sea bass (sampling no. 4) from three farms with different rearing systems (extensive, land intensive and intensive sea cages) and stored for 3, 6, 10, 13 and 17 days in boxes covered with ice and kept in a refrigerated room at 2°C confirmed the absence of an effect of the storage time on biometric traits and carcass and fillet percentages. The sensorial evaluation confirmed a significant increase of QIM scores and a high correlation (R2 from 0.84 to 0.95 depending on the farm considered) with the days of storage. The QIM evolution, however, evidenced a curvilinear trend, with a quick freshness degradation during the first days, which was slow until 10-13 days of storage (normalized QIM corresponding to 30-35% of the total loss of freshness) and, at last, fast between 13 and 17 days of storage, when freshness impairment reached 65-70%. The complete loss freshness in the storage conditions used in the present trial was estimated to

Reactivity of growing rabbits under different housing systems

To evaluate the effect of housing system (bicellular cages vs collective pens) and, within collective systems, of pen size and stocking density on animal reactivity, a total of 456 rabbits was kept in pairs in bicellular cages or in large groups (20 to 54 animals) in collective cages of different sizes (small vs large) with wooden slatted floor and at two stocking densities (12 vs 16 rabbits/m2). The effects of the rearing system were assessed on rabbit reactivity to humans (tonic immobility test at 55 and 72 days of age) and against a new environment (open field test at 56 and 75 days of age). The reactivity of rabbits at the tonic immobility test was not affected by the age of the animals at the test, whereas at the open field test the younger rabbits spent less time in biting walls and edges of the enclosure (2.58 vs 6.33 sec; P<0.001) and showed a higher number of jumps (0.25 vs 0.01; P<0.01) and alerts (0.29 vs 0.05; P<0.01) than the older rabbits. With reference to the effect of the housing system, the percentage of rabbits that did not fall in immobility tended to be lower (6.2 vs 23.5%; P=0.09) and the amount of rabbits that rested in tonic immobility from 1 to 179 second tended to be higher (90 vs 73%; P=0.09) in the rabbits kept in bicellular cages than in those housed in collective cages. At the open field test, the rabbits reared in bicellular cages crossed more squares (47.5 vs 31.2, P<0.01) and moved more (58.3 vs 40.4 sec, P<0.01) than the rabbits in collective cages, whereas they stand in a vigilance position for a shorter time (38.7 vs 84.6 sec, P=0.04). Neither the cage size nor the stocking density in the collective pens significantly affected rabbit reactivity. In conclusion, the rabbits housed in bicellular cages showed a higher fear level against man but were more prone to exploration in a new environment in comparison with group-housed rabbits

Effect of cage floor and stocking density on growth performance and welfare of group-housed rabbits

Two hundred forty rabbits weaned at 36 d (LW=1103\ub141 g) were housed in groups to evaluate the effect of stocking density and type of cage floor on behaviour, health status, growth performance, and carcass and meat quality. The rabbits were put in groups of 6 into 40 cages of two sizes (78 x 64 cm or 58 x 64 cm) corresponding to two stocking densities (D12, 12.1 rabbits/m2 vs. D16, 16.2 rabbits/m2). Within density, four types of floor were compared (steel slat, plastic slat, wire net and straw litter on wire net) according to a 2 x 4 factorial arrangement with five replications (cages). The rabbits were fed a unique diet (CP: 15.8%, ADF: 19.3%, DE: 9.8 MJ/kg). No antibiotic was added to feed or water. Rabbit reactivity was assessed by the tonic immobility and open-field tests at 70 and 74 d of age. Rabbits were slaughtered at 78 d to evaluate carcass and meat quality. Femur dimensions and resistance to fracture were measured. Sanitary status and growth performance were highly satisfying in all treatments: growth rate averaged 45.5 g/d and final weight 2967 g, with a feed conversion rate of 3.49. Stocking density did not affect growth performance, meat quality, nor animal reactivity. In contrast, the type of floor significantly affected growth performance: rabbits kept on straw bedded floor showed the lowest final weight (2865 g vs. 3000 g on average, P=0.03), weight gain and feed intake. Differences in carcass and meat quality mainly depended on the weight at slaughter: dressing percentage and separable fat of the carcass were lower (P<0.01) in the lightest rabbits kept on straw (58.6% and 2.3%, respectively) compared to the heavier animals of the other three experimental groups (average values 59.9% and 3.0%, respectively). The type of floor also affected animal reactivity: the number of attempts necessary to induce immobility, considered inversely correlated with fear towards humans, was lower in rabbits kept on straw; these rabbits also showed a more passive reaction during the open field test, spending less time exploring and more time in an immobile state (P<0.01) in comparison with the animals housed in the cages with plastic slat or wire net floors

Riduzione del livello proteico e aumento del rapporto fibra solubile/amido in diete per conigli in accrescimento

From 29 d of age until slaughter (78 d), 282 rabbits were fed six diets formulated in order to evaluate the combined effect of dietary protein level (CP: 13.9 vs. 15.4 vs. 17.5%) and soluble fibre to starch ratio (0.5 vs. 1.1). Health status was good in all groups. When dietary CP decreased, diet DM digestibility, daily growth rate and caecal volatile fatty acid (VFA) concentration significantly decreased. When soluble fibre to starch ratio increased, diet DM and fibre fractions digestibility significantly raised, feed intake decreased and feed conversion improved; at caecum, VFA concentration increased and N-ammonia level diminished. In conclusions, decreasing dietary CP until 13.9% impaired rabbit growth, while replacing starch with soluble fibre had advantages on both performance and caecal fermentations

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 (PCBtot) and of the seven indicator congeners (PCB7) (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 fat, respectively) with respect to sea bass from the other systems (average values: 179.7 and 123.2 ng/g fat) (P< 0.001). When the values were expressed on fresh muscle weight, PCBtot and PCB7 were lower in extensively-reared sea bass (3.412 and 2.266 ng/g 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). PCB7 concentration expressed in ng/g fat and in ng/g 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)

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

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&deg;C. Sea bass weighted 308&plusmn;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

Feeding growing rabbits with low dietary protein level and high soluble fibre to starch ratio

To evaluate the effect of decreasing dietary protein and replacing starch with soluble fibre on digestive physiology and performance, 246 hybrid rabbits (782\ub153 g LW) weaned at 33 d of age were divided into six groups and fed ad libitum until slaughter (76 d) six iso-ADF diets. The diets varied according to two protein levels (15.2% and 16.2%) combined with three soluble fibre to starch ratios (0.2, 0.6 and 1.5) obtained by replacing starch (20.9 to 9.1%) with soluble fibre (4.8% to 13.6%). Data were submitted to ANOVA by GLM procedure of SAS. The diet with 16.2% CP and 0.2 soluble fibre to starch ratio determined the highest mortality rate (17.1 vs 1.7%; P<0.001) compared to the other diets. When dietary CP increased, the digestibility of dry matter (61.5% to 62.6%), gross energy (62.0% to 63.0%) and aNDF (29.8% to 32.3%) significantly (0.001<P<0.10) raised and caecal volatile fatty acids (VFA) increased (59.0 to 68.4 mmol/L; P=0.01). Growth performance and slaughter traits were not affected by the protein level. When soluble fibre to starch ratio raised, the digestibility of dry matter and gross energy did not change, while the digestibility of aNDF (26.4 to 35.2%) and ADF (16.7 to 26.7%) linearly increased (P<0.001). Caecal VFA concentration (56.0 to 67.3 mmol/L) and acetate proportion linearly increased, while butyrate and valerate proportions decreased (0.01<P<0.05). Growth performance was similar among groups, while at slaughter the proportion of the gastro-intestinal tract linearly increased (17.7 to 18.4%; P<0.01) without affecting dressing percentage. Meat pH linearly decreased and L*, a* and b* colour indexes increased (0.01<P<0.05). In conclusion, feeding rabbits with low-protein and high-soluble fibre to starch ratio diets reduced mortality, improved digestive efficiency and intestinal environment without affecting growth performance

Enqu\ueate sur les \ue9levages de lapins en V\ue9n\ue9tie: R\ue9sultats de gestion technique et estimation des rejets azot\ue9s

A survey on rabbit farms in Veneto Region: technical data and nitrogen excretion estimate. A survey was performed on 48 rabbitries (breeding and fattening) located in Veneto Region to collect technical information and calculate nitrogen balance. Farms show great variability in dimensions (1 216\ub1885 reproducing does and 7 495\ub15 852 fattening rabbits), management and productivity. Fertility (76.8%) and other data of reproductive efficiency are significantly correlated with the number of rabbits sold/doe/year, while independent from the number of reproducing does in the farm. The number of rabbits sold/doe/year is 42.8 on average (from 28.9 to 60.9). The N excreted by the doe and its offspring is on average 7.40\ub11.48 kg/year and significantly influenced by slaughter weight (P=0.05) and number of rabbits sold/doe/year (P<0.001). The total nitrogen output of the whole rabbit production process corresponds to 65\ub15 g of N per kg of rabbit produced alive