Academic literature on the topic 'Restriction digestion'

Total DNAs from nine strains of Acetobacter xylinum, two strains of Acetobacter aceti, and one Acetobacter pasteurianus strain were examined for the extent of digestion by various restriction endonucleases. The majority of the endonucleases cleaved the total DNAs with a frequency expected from the number of sites present in DNA sequences deposited in the GenBank data base. However, the restriction enzyme digestions identified two different genomic DNA modifications in Acetobacter. One sequence-specific modification protected total DNAs from seven of the A. xylinum strains against cleavage by EcoRI (GAATTC). Digestion of total DNAs from A. xylinum ATCC 10245 (DNA not cut by EcoRI) and the closely related A. xylinum NRCC 17005 (DNA cut by EcoRI) with Tsp509I (AATT) revealed differences in restriction frequencies that indicated methylation of the first or second adenine within GAATTC. Another sequence-specific modification rendered total DNAs from all the 12 strains recalcitrant to digestion by HinfI. The latter modification indicated that species of the genus Acetobacter contain a solitary DNA methyltransferase that probably methylates adenine in GANTC.Key words: Acetobacter, genomic DNA, modifications, EcoRI, HinfI.

Polytene chromosomes of Drosophila virilis were treated with AluI and HaeIII restriction endonucleases. Both enzymes were capable of extensively digesting chromosomal DNA, with the exception of some regions that contain repetitive DNAs. Moreover, a comparison was made between our data and the data already obtained with the same enzymes in D. melanogaster. On this basis, AluI digestion showed that the 5S RNA genes of D. virilis and D. melanogaster have different base composition, while digestion with HaeIII revealed resistance of the histone genes in D. virilis, contrary to what was previously found in D. melanogaster. Key words: restriction endonucleases, 5S RNA genes, histone genes, polytene chromosomes, Drosophila species.

ABSTRACT A physical map of the apple proliferation phytoplasma strain AT chromosome was constructed from genomic DNA extracted from diseased tobacco plants. The map was generated with single and double digestions of the chromosome with BssHII, SmaI,MluI, and ApaI restriction endonucleases and resolving the fragments by pulsed-field gel electrophoresis. Partial digestion and Southern blot analysis were used to assist in the arrangement of the 14 contiguous restriction fragments obtained. From the restriction fragments generated by double digestions, the size of the circular chromosome was calculated to be approximately 645 kb. Locations of the two rRNA operons, the operon including thefus and tuf genes, and three other genes were placed on the map. Genome sizes and BssHII restriction profiles of apple proliferation strain AP15 and the pear decline and European stone fruit yellows phytoplasmas were different from that of strain AT.

A specific diagnostic method using the polymerase chain reaction, together with restriction endonuclease digestion patterns, was developed for members of the “ Mycoplasma mycoides cluster” that normally occur in the United States (i.e., Mycoplasma mycoides subsp. mycoides Large Colony and Mycoplasma capricolum subsp. capricolum in addition to “cluster” mycoplasma, bovine serogroup 7, and Mycoplasma putrefaciens. The digestion of “cluster” polymerase chain reaction DNA (1,225 bp) amplification products with restriction enzymes Asel and SspI gave mycoplasma species-specific patterns for all strains of M. mycoides subsp. mycoides Large Colony, M. capricolum subsp. capricolum, and bovine group 7 tested. Moreover, we found a nonspecific amplification product for M. putrefaciens that occurred with the oligonucleotide primers used for the “ M. mycoides cluster” reaction. However, the restriction endonuclease digestion patterns observed with the restriction enzymes AluI, AseI, and SspI for M. putrefaciens were different than the digestion patterns obtained for the other “cluster” mycoplasmas. This report confirms the usefulness of polymerase chain reaction DNA amplification allied with restriction enzyme digestion profile analysis for the rapid and specific identification of mycoplasmas belonging to the “ M. mycoides cluster” and M. putrefaciens.

La restriction temporaire de l'ingestion du lapin après son sevrage est maintenant une stratégie d'alimentation couramment employée en cuniculture. L'objet de cette synthèse est de présenter les différents effets d'une limitation de l'ingestion sur la santé, la physiologie digestive et l'efficacité alimentaire du lapin en croissance. Même si une restriction alimentaire conduit à une croissance plus lente, ces stratégies sont désormais utilisées par plus de 85% des éleveurs français. En effet, elles permettent de réduire les risques de mortalité et de morbidité post-sevrage par troubles digestifs, par exemple par l'entéropathie épizootique du lapin. De plus, la conversion alimentaire est améliorée, plus particulièrement lorsque les lapins sont de nouveau alimentés librement, en raison d'une importante croissance compensatrice. Cette meilleure efficacité alimentaire est associée à un transit plus lent et à une meilleure digestion, bien qu'on observe des interactions avec la composition chimique de l'aliment. La physiologie digestive est par ailleurs peu modifiée, en particulier la morphométrie de la muqueuse intestinale, l’activité fermentaire et le microbiote caecal. La qualité de la viande est peu affectée par la restriction alimentaire, alors qu'on observe une baisse de l'état d'engraissement des carcasses et une légère dégradation du rendement à l'abattage. Les effets d'une limitation de l'ingestion sur le comportement et le bien-être animal sont discutés, sachant que le jeune lapin présente une adaptation très rapide aux stratégies de restriction. Ainsi, les stratégies de restriction peuvent améliorer la rentabilité de l'atelier cunicole, mais elles doivent être adaptées à chaque situation d'élevage.

The genetic variability of 40 accessions of_C. arabica was evaluated using a combination of the random amplified polymorphic DNA (RAPD) technique and restriction digestion of genomic DNA. The genetic variability and the relatedness among all accessions were initially evaluated using 195 RAPD primers which revealed a very low level of genetic variation. To improve the efficiency in the detection of polymorphism, the genomic DNA of all accessions were submitted to digestion with restriction endonucleases prior to PCR amplification. A total of 24 primers combined with restriction digestion of DNA rendered 318 bands, of which 266 (83.65%) were polymorphic. The associations among genotypes were estimated using UPGMA-clustering analysis. The accessions were properly clustered according to pedigree and agronomic features. The ability to distinguish among coffee accessions was greater for RAPD plus restriction digestion than for RAPD alone, providing evidences that the combination of the techniques was very efficient for the estimation of genetic relationship among_C. arabica genotypes.

Dans un contexte de limitation de l'utilisation des antibiotiques, de nouvelles stratégies doivent être mises en place pour préserver la santé des animaux, en particulier lors du sevrage. En cuniculture, les stratégies de limitation de l'ingestion permettent de réduire les troubles digestifs en post sevrage et améliorent l'efficacité alimentaire, mais induisent inévitablement un retard de croissance et une baisse du rendement à l'abattage. Ce travail de thèse avait pour objectif d'une part d'optimiser les performances de croissance et de rendement à l'abattage des animaux soumis à une restriction alimentaire via une modulation de la quantité et de la qualité énergétique des aliments et d'autre part d'expliciter les mécanismes physiologiques sous-jacents aux effets bénéfiques d'une ingestion restreinte sur la santé et l'efficacité alimentaire. Nous avons démontré que dans le cadre d'une stratégie de restriction alimentaire un aliment riche en énergie digestible permet d'optimiser la croissance (+2%), le rendement à l'abattage (+0,6 points) et l'efficacité alimentaire (+11%), via notamment une amélioration de l'efficacité digestive, sans pénaliser les paramètres sanitaires, mais ne permet de rattraper que partiellement le retard de croissance induit par la restriction alimentaire (-3% de poids à l'abattage par rapport aux animaux nourris à volonté). Un aliment riche en amidon était favorable à la croissance de ces animaux et en particulier au rendement à l'abattage et n'avait pas d'effet délétère sur les paramètres sanitaires. La restriction alimentaire et la concentration énergétique alimentaire dans une moindre mesure, modulaient la réponse immunitaire via une réduction de la réponse humorale digestive (IgA intestinaux) et systémique (IgA et IgG circulants) sans modification de la réponse inflammatoire. L'activité du microbiote caecal était quant à elle modulée par la masse d'aliment ingérée alors que le profil de la communauté bactérienne caecale, sa diversité et sa richesse ne semblaient pas modifiés par la restriction alimentaire. Toutefois l'abondance relative de certaines familles (Eubacteriaceae, Peptococcaceae et Christensenellaceae) et genres montraient des variations spécifiques à la restriction ou à la concentration énergétique de l'aliment. L'ensemble de ces résultats indiquent que les relations entre les mesures physiologiques et les effets bénéfiques de la restriction alimentaire sur la santé digestive restent complexes et suggèrent l'implication d'autres paramètres métaboliques non évalués. Des hypothèses complémentaires de travail doivent ainsi être envisagées Toutefois nos travaux établissent l'intérêt économique de la restriction alimentaire, quel que soit le contexte sanitaire, et celui de l'utilisation d'aliments à haute valeur énergétique sur les performances zootechniques. Notre étude ouvre dès lors des perspectives de recherches complémentaires d'optimisation des stratégies alimentaires via une modulation de la durée de restriction alimentaire et de la qualité énergétique des aliments
With the reduction in antibiotic use new strategies are required in order to preserve animal health, particularly around weaning. In rabbit breading feed restriction strategies allow for the reduction of post-weaning digestive disorders and improve feed efficiency, but are inevitably responsible for a reduced growth and carcass yield at slaughter. This work aimed to optimize the growth performances and slaughter yield of restricted fed rabbits through a modulation of the dietary energy concentration and quality. The second objective of this work was to explain the physiological mechanisms underlying the beneficial effects of feed restriction upon health and feed efficiency. We demonstrated that, under a restriction strategy, a diet rich in digestible energy increased growth (+2%), slaughter yield (+0.6 points) and feed efficiency (+11%), through an improved digestive efficiency, without penalizing the sanitary parameters. The reduced growth induced by feed restriction was however only partially compensated for (-3% in final weight compared to the ad libitum fed animals). A diet rich in starch induced a higher growth and slaughter yield and did not penalize the sanitary parameters under a restriction strategy. Feed restriction and, to a lesser extent, the dietary energy concentration, modulated the immune response through a reduced humoral response at the digestive (fecal IgA) and systemic (plasmatic IgA and IgG) levels without modifying the inflammatory response. The cecal microbial activity was modulated by the amount of feed ingested while the cecal bacterial community profile, diversity and richness were not affected by the feed intake level. However, the relative abundance of certain families (Eubacteriaceae, Peptococcaceae and Christensenellaceae) and generas demonstrated specific variations according to the feed intake level and the dietary energy concentration. These results indicate that the relationship between the physiological measurements and the beneficial effects of feed restriction upon health remain complex and suggest the implication of other metabolic parameters that weren't measured. Complementary work hypothesis must therefore be considered. This work however enabled us to establish the economic advantage of feed restriction strategies regardless of the sanitary status and demonstrated the beneficial effects of a high energy diet on growth parameters. Our study opens the door to new complementary research projects regarding the optimization of the feeding strategies through for instance the modulation of the restriction length and the dietary energy quality

Les attentes sociétales s’orientent vers une consommation saine, et provenant de systèmes agricoles durables. En filière cunicole, la maîtrise des pathologies digestives nécessite le recours à l'antibiothérapie curative ou préventive. La recherche d’alternatives à l’utilisation d’antibiotiques en élevages cunicoles est donc primordiale pour augmenter la durabilité de cette production. Les stratégies de limitation de la quantité d’aliment ingérée sont une des solutions possibles à ce problème, puisqu'elles améliorent la résistance du jeune lapin aux troubles digestifs. Ce travail de thèse a pour objectif d’étudier les mécanismes sous-jacents à cet effet favorable des stratégies de rationnement, et aussi d'analyser le comportement alimentaire du lapin restreint en relation avec son bien-être. Cet objectif se scinde en deux parties étudiées. La première partie a pour but de déterminer quelle caractéristique de la restriction alimentaire limite les troubles digestifs en engraissement. La seconde partie s’intéresse aux paramètres biologiques potentiellement influencés par cette stratégie d’alimentation. Les paramètres considérés sont reliés à plusieurs domaines de biologie : enzymologie, histométrie, écosystème bactérien cæcal. Une restriction de l'ingéré de -25% réduit la croissance mais améliore significativement l’efficacité digestive (de 4 à 6% entre 28 et environ 50 jours d'âge) des lapins en engraissement, qui peut s'expliquer par une plus forte digestibilité des fractions protéique (4,5%), énergétique (5,3%) et fibreuses (NDF : 8,9%, ADF : 9,7%, hémicelluloses: 7,9%, cellulose : 11,5%). Cependant, la structure, la diversité et la densité de la communauté bactérienne cæcale sont peu modifiées chez l'animal restreint sain. Des modifications du comportement alimentaire ont été soulignées au cours de ce travail. Ainsi, le rythme d’ingestion, fonction du rythme nycthéméral pour les lapins nourris à volonté, est dépendant du moment de distribution de l’aliment pour les animaux restreints. Après 18 jours de restriction, les lapins ingèrent un tiers de la quantité qui leur est distribuée en 2 heures, et la totalité en moins de 10 heures. Mais aucune agressivité ou compétition n’a été observée entre les animaux restreints. Plusieurs pistes peuvent expliquer l’efficacité de cette stratégie d’alimentation sur la santé digestive du lapereau. Ainsi, les résultats obtenus au cours de la reproduction d’une colibacillose (Escherichia coli O128:C6) suggèrent une stabilisation de l’écosystème iléal par la restriction alimentaire après l’infection. D'autre part, au niveau cæcal l'activité des communautés bactériennes serait modulée, même si pour ce modèle, l'effet d'une ingestion limitée semble faible sur le statut sanitaire. Enfin, l’alternance de périodes de satiété et de périodes de faim stimule la libération sanguine d’hormones (ghréline notamment) qui pourraient moduler la fonction immunitaire. En perspectives, il serait pertinent d'étudier plus précisément les fonctions liées au statut immunitaire ou endocrinologique. De plus, l'étude plus approfondie de la communauté bactérienne cæcale, en ciblant certaines espèces, pourrait apporter un complément d’informations sur les interactions entre ingestion et symbiote digestif et lors d'une approche comparée de 2 modèles pathogèniques : EPEC vs. EEL
Societal expectations are moving towards healthy food from sustainable farming systems. In rabbit industry, control of digestive diseases requires the use of curative or preventive antibiotics. The search for alternatives to the use of antibiotics in rabbit breeding is thus crucial to improve sustainability of this production. Strategies for limiting the amount of feed ingested are one possible solution to this problem, since they improve the digestive resistance of young rabbits. This thesis aims to study the mechanisms underlying this positive effect of restriction strategies, and also to analyze the feeding behaviour of restricted rabbit in relation to their welfare. This objective is divided into two parts. The first part aims to determine which characteristic of feeding restriction limits the digestive disorders in fattening. The second part deals with the biological parameters potentially influenced by this feeding strategy. The parameters considered are related to several areas of biology: enzymology, histometry, digestive bacterial ecosystem A reduction of feed intake of -25% reduced growth, but significantly improved digestive efficiency (4 to 6% between 28 and 50 days old) of fattening rabbits which can be explained by a higher protein digestibility (4.5%), energy (5.3%) and fibres (NDF: 8.9%, ADF: 9.7%, hemicellulose 7.9%, cellulose: 11.5%). However, the structure, diversity and density of the caecal bacterial community are little changed in the healthy animal fed restricted. Changes in eating behaviour were highlighted during this work. Thus, the rhythm of intake, depending on the circadian rhythm in rabbits fed ad libitum, is function of the feed distribution time for restricted animals. After 18 days of restriction, rabbits ingest in 2 hours the third of the quantity supplied, and the entire amount within 10 hours. No aggression or competition was observed between animals. Several hypotheses could explain the effectiveness of this strategy on digestive health in young rabbit. Thus, the results obtained during the reproduction of colibacillosis (Escherichia coli O128: C6) suggest a stabilization of the ileal ecosystem after infection. On the other hand, the main activity of bacterial communities of caecum would be modulated, even if for this model a limited intake moderately modified the sanitary status. Finally, the alternation of periods of satiety and hunger may stimulate the release of hormones (e.g. ghrelin) that could modulate immune function. In perspective, it would be appropriate to study more precisely the functions related to immune or endocrine status.In addition, a deeper study of the caecal bacterial community by targeting some species could provide additional informations on the interactions between intake and digestive symbiote, and on a comparative approach of the two pathogenic models: EPEC vs. REE

2006/2007
Next-generation DNA detection arrays are expected to achieve unprecedented sensitivity, reducing the minimum amount of genetic material that can be directly (PCR-free and label-free) and quantitatively detected, up to the single cell limit. To realize these goals, we propose a new method for the miniaturization of DNA arrays to the nano-scale, which has the unique capability of controlling the packing quality of the deposited bio- molecules. We used NanoGrafting, a nano-lithography technique based on atomic force microscopy (AFM), to fabricate well ordered thiolated single stranded (ss)-DNA nano-patches within a self-assembled monolayer (SAM) of inert thiols on gold surfaces. By varying the “writing” parameters, in particular the number of scan lines, we were able to vary the density of the supported DNA molecules inside the nano-patches in a controlled manner. Our findings can be resumed in two parts: 1) Combining accurate height and compressibility measurements, before and after hybridization, we demonstrate that high-density ss-DNA nanografted patches hybridize with high efficiency, and that, contrary to current understanding, is not the density of probe molecules to be responsible for the lack of hybridization observed in high density ss-DNA SAMs, but the poor quality of their structure. 2) Dpn II enzymatic reactions were carried out over nanopatches with different molecular density and different geometries. Using nanopatch height measurements we are able to show that the capability of the Dpn II enzyme to reach and react at the recognition site significantly depends on the molecular density in the nanopatches. In particular the inhibition of the reaction follows a step-wise fashion at relatively low DNA densities. These findings suggest that, due to the enzyme size, it is possible to tune the efficiency of an enzymatic reaction within surface-bound DNA nanostructures by changing only the crowding of DNA on the surface and without introducing any further physical or chemical variable.
XIX Ciclo
1979

The application of feed restriction strategies to meat rabbit production is focused on two main aspects: 1) the improvement of animal health status by reducing mortality and morbidity due to digestive troubles; 2) the increase in the global farm efficiency by enhancing feed conversion and decreasing the costs related to antibiotic treatments. Both of these issues are of great interest in view of guaranteeing an economic sustainability to farmers and meeting the European regulations in terms of food safety. Hence, over the last decades, the effects of feed restriction strategies in growing rabbits have been widely investigated. Most of the studies has carried out feeding restriction during the first three or four weeks after weaning, with the aim to obtain feeding levels ranging from 60% to 90% of ad libitum, and free feeding during the last phase of fattening (from one to three weeks). Quantitative feed restrictions have been obtained directly by reducing the amount of diet supplied or indirectly by limiting the feeding time or the drinking time. Furthermore, qualitative feed restriction has been performed by reducing the energy level in the diets supplied to animals. The choice of restriction method should take into account the rearing facilities and equipment, the environmental conditions, and the impact on animal welfare. The literature reported that rationing programs could represent a valid tool to reduce the incidence of digestive troubles, to increase diet utilization and to improve feed efficiency in growing rabbits. However, the protective effect of feed rationing on gut health is only limited to the restriction phase, while the incidence of digestive disease could even increase during fattening in rabbits previously restricted. Therefore, the re–feeding technique represents a critical point, but few studies have been focused on this issue. Moreover, the multifactorial origin of ERE makes difficult the interpretation of the variable and sometimes contrasting results among studies. On the other hand, the improvement of feed conversion seems to be a constant effect, but the economic benefits can be limited because of a longer fattening period is often required to achieve the complete recover of the animals in terms of live weight and avoid a substantial decrease in slaughter yield. Indeed, the economic aspects of feed restriction techniques should be carefully evaluated especially in the markets that require high slaughter weights (e.g. Italian market). The present thesis aimed to define an effective feed restriction program for enhancing feed efficiency and gut health in growing rabbits, without impairing slaughter traits, carcass and meat quality. The goal was pursued by focusing on three specific objectives (i) to evaluate the effect of quantitative feed restriction systems in individually-housed rabbits; ii) to develop an adequate time–based feed restriction program in group–housed rabbits; iii) to optimize the management of the re–feeding phase. These points were developed in four experimental contributions whose working plan and main results are summarized below: First contribution: Effects of feed restriction system and slaughter age in growing rabbits The effect of the feeding system (AL: ad libitum vs. D: day–by–day restriction system vs. W: week–by–week restriction system) on digestive efficiency, sanitary status, growth performance, carcass traits, and nitrogen excretion was evaluated on 282 commercial crossbred rabbits kept in individual cages from weaning (36 d of age) to slaughter. The effect of slaughter age (73 vs. 80 d of age) was also assessed. The feed restriction was based on the administration of a restricted amount of the diet which increased from 80% to 100% of AL intake in the first three weeks after weaning according to two feeding curves characterized by either small daily increments (+4 g/d; D group) or large weekly increments (+23 g/week on average; W group). From the beginning of the 4th week, the amount of feed supplied for both restricted groups was increased by 4 g/d for 9 consecutive d in order to prevent high picks in food ingestion, then all rabbits were fed ad libitum until commercial slaughter. No antibiotic treatment was administered during the trial. The apparent digestibility of the post–weaning diet was measured on 36 rabbits (12 per feeding system) from 49 to 53 d of age (during the restriction phase), while the digestibility of the fattening diet was measured on 36 rabbits (12 per feeding system) from 64 to 68 d of age (during the ad libitum period). At the moment of the first digestibility trial, the feed ingestion of the restricted group was equal to 95% of AL group and therefore only the digestibility of crude protein was increased (P<0.001). During the second period, no residual effect of the previous restriction treatment was observed on diet digestibility. In the whole trial, mortality, morbidity and sanitary risk reached respectively 12.7%, 11.3% and 24.0% on average. Mortality and sanitary risk were significantly (P<0.05) reduced in restricted rabbits compared to those fed ad libitum ( 12.0 percentage points), in particular when a day–by–day restriction curve was applied ( 14.2 percentage points). In the first three weeks the feed restriction level was equal to 91% in D group and 93% in W group; daily growth decreased in both restricted groups ( 7.5% with respect to AL) whereas feed conversion did not differ among groups. In the second period only W rabbits showed higher feed intake (+4.2%) and weight gain (+14.5%), and a better feed conversion ( 3.2%) compared to AL rabbits. Final live weight (on average 2748 g), feed conversion ratio (3.07), cold dressing percentage (59.8%) and other carcass traits were not affected by the feeding treatment. The daily nitrogen excretion was reduced ( 0.08 g/d per rabbit; P<0.05) in the D group respect to AL group. The increase of slaughter age from 73 to 80 d significantly increased final live weight (+7.5% g; P<0.001) and feed intake (+4 g/d, P<0.05), reduced daily weight gain ( 3.1 g/d; P<0.001) and impaired feed conversion (2.92 vs. 3.22; P<0.001). All carcass traits were greatly (P<0.01) modified by delaying slaughter age; carcass weight increased (1563 g to 1705 g) as well as dressing percentage (59.3% to 60.5%), carcass fatness and muscularity, whereas the incidence of full gut decreased ( 0.7 percentage points). Nitrogen excretion was also increased (+0.21 g/d per rabbit) in older rabbits. In conclusion, feed restriction improved rabbit health status without impairing growth performance and carcass traits. The day–by–day restriction curve reflected better the feeding behaviour of growing rabbits compared to the week–by–week curve, allowing to obtain a feeding level similar to that expected. However, the application of this type of restriction appears difficult in commercial farms because it is time and labour consuming if automatic feeding systems are not available and could not to be adequate with group–housed rabbits. The delay of slaughter increased dressing percentage, but impaired feed conversion and increased environmental nitrogen excretion. Second contribution: Time–based feed restriction and group composition for gender: effects on growth performance, feeding behaviour and meat quality of growing rabbits The effect of the feeding system (AL: ad libitum vs. R: feed restriction) and the sex–based group composition (X: only females vs. Y: only males vs. Z: mixed sexes) on growth performance, feeding behaviour, slaughter traits and meat quality was evaluated on 288 crossbred rabbits (144 females and 144 males), housed from weaning (33 d of age) to slaughter (75 d of age) in 18 collective pens (1 m2; 16 animals per pen). A time–based feed restriction was realized by increasing the access time to the feeders (allowed mainly during the hours of darkness) step–by–step (+1 h every 3–4 d) from 10 h/d to 16 h/d in the first three weeks. After that, feeding time increased gradually (+1 h/d) until reaching the free access to the feeders. During the first three weeks, an average restriction level equal to 95% of ad libitum was obtained. During the first three weeks, feed intake decreased (128 vs. 122 g/d; P<0.01) and feed conversion improved (2.42 vs. 2.29; P<0.001) in restricted rabbits in comparison with rabbits fed ad libitum. In the second trial period, the previously restricted rabbits showed a worse feed conversion (2.70 vs. 2.83; P<0.001) compared to rabbits always fed ad libitum. In the whole trial, growth performance were not affected by the feeding system. The feed restriction greatly modified the feeding behaviour of R rabbits, which showed a higher hourly feed consumption compared to AL ones throughout the time of access to the feeders. Once fed freely, R rabbits showed an intake pattern similar to that of AL rabbits within two days. The feed restriction did not affect slaughter weight (on average 2860 g), dressing percentage (61.0%) or meat quality. In the first trial period growth performance did not change according to the sex of the animals, while in the second period the pens with only females or with mixed sexes showed higher daily growths compared to those with only males (47.0 g/d vs. 43.8 g/d vs. 46.1 g/d for X, Y and Z groups, respectively; P<0.01). At the same time, the feed conversion ratio decreased in pens X and Z in comparison to Y ones (3.66 vs. 3.91 vs. 3.72; P<0.01). Considering the whole rearing period, daily weight gain, feed intake and feed conversion did not change according to the group composition and the animals reached similar live weights at the end of trial. Transport losses were higher in X pens compared to Y ones (3.00% vs. 2.45% vs. 2.80%; P<0.01), while the cold dressing percentage (60.2% vs. 61.8% vs. 61.0%; P<0.001) and the head proportion on carcass (7.41% vs. 7.65% vs. 7.60%; P<0.05) were higher in males. Meat pH, thawing losses and shear force of l. lumborum were significantly (0.05L’applicazione di strategie di restrizione alimentare nei conigli in accrescimento si focalizza su due obiettivi principali: 1) il miglioramento dello stato di salute con la riduzione di mortalità e morbilità causate da patologie digestive; 2) l’aumento dell’efficienza globale delle aziende con l’ottimizzazione dell’indice di conversione e la diminuzione dei costi legati alla somministrazione di antibiotici. Entrambi questi temi sono di grande interesse al fine di garantire la sostenibilità economica per gli allevatori e rispettare le normative Europee in tema di scurezza alimentare. Per questi motivi, nel corso degli ultimi decenni, gli effetti delle strategie di restrizione alimentare nei conigli in accrescimento sono stati ampiamente studiati. Nella maggior parte degli studi, il razionamento è stato attuato durante le prime tre o quattro settimane successive allo svezzamento, con l’obiettivo di ottenere livelli di alimentazione compresi tra il 60% e il 90% dell’ingestione ad libitum, seguito da un periodo di alimentazione a volontà durante le ultime fasi dell’ingrasso (da una a tre settimane). Restrizioni quantitative sono state ottenute direttamente, riducendo la quantità di mangime somministrato agli animali, o indirettamente, limitando il tempo di accesso al cibo o all'acqua. Inoltre, restrizioni qualitative sono state ottenute riducendo il contenuto energetico delle diete fornite agli animali. La scelta del metodo per applicare la restrizione alimentare deve tenere in considerazione le attrezzature disponibili in allevamento, le condizioni ambientali e di stabulazione nonché l’impatto sul benessere degli animali. La letteratura scientifica riporta che i programmi di razionamento rappresentano un valido strumento per ridurre l’incidenza dei problemi digestivi, aumentare l’utilizzazione digestiva delle diete e migliorare l’efficienza alimentare nei conigli in accrescimento. Tuttavia, l’effetto protettivo del razionamento sulla salute intestinale degli animali si limita alla fase di restrizione, mentre il rischio per i conigli precedentemente razionati di contrarre malattie digestive spesso aumenta durante la fase di re–alimentazione. Pertanto, la gestione di quest’ultima fase rappresenta un punto critico, ma pochi studi hanno trattato questa problematica. Inoltre, l’origine multifattoriale dell’enteropatia epizootica del coniglio rende difficile l’interpretazione dei risultati diversi e talora contraddittori ottenuti nei vari studi. Se da un lato il miglioramento dell’indice di conversione sembra essere un effetto abbastanza ripetibile, i vantaggi in termini economici potrebbero essere limitati considerando la necessità di allungare la fase di ingrasso per permettere un completo recupero delle performance produttive (pesi vivi finali) ed evitare considerevoli diminuzioni delle rese di macellazione. Infatti, gli aspetti economici legati all'utilizzo di strategie di riduzione alimentare nella produzione del coniglio da carne devono essere attentamente valutati, specialmente nei paesi dove il mercato richiede pesi di macellazione elevati come l’Italia. La presente tesi ha avuto lo scopo di definire programmi di razionamento efficaci nel migliorare l’efficienza alimentare e la salute intestinale nei conigli in accrescimento, senza compromettere i risultati di macellazione, le caratteristiche della carcassa e la qualità della carne. Lo scopo è stato perseguito focalizzandosi su tre obiettivi principali: (i) valutare l’effetto di un sistema di restrizione quantitativo in conigli alloggiati individualmente; (ii) sviluppare un’adeguata restrizione basata sul tempo di accesso al cibo in conigli stabulati in recinti collettivi; (iii) ottimizzare la gestione della fase di re–alimentazione. Questi punti sono stati affrontati in quattro contributi sperimentali la cui organizzazione e principali risultati sono riassunti di seguito: Primo contributo: Effetto del sistema di restrizione alimentare e dell’età di macellazione in conigli in accrescimento L’effetto del sistema di alimentazione (AL: ad libitum vs. D: sistema di razionamento progressivo con variazioni giornaliere vs. W: sistema di razionamento scalare con variazioni settimanali) su efficienza digestiva, stato di salute, performance produttive, caratteristiche della carcassa e bilancio dell’azoto è stato valutato utilizzando 282 conigli ibridi commerciali allevati in gabbie monocellulari dallo svezzamento (36 d di età) alla macellazione avvenuta a due età (73 vs. 80 d). La restrizione alimentare era basata sulla somministrazione di ridotte quantità di mangime crescenti dall'80% del consumo AL allo svezzamento al 100% alla fine della terza settimana dopo lo svezzamento in funzione di due curve di alimentazione caratterizzate da piccoli incrementi giornalieri (+4 g/d; gruppo D) o da grandi aumenti settimanali (+23 g/settimana in media; gruppo W). Dall'inizio della quarta settimana la quantità di mangime fornito in entrambi i gruppi razionati è stata aumentata di 4 g/d per 9 giorni consecutivi al fine di prevenire bruschi picchi di ingestione alimentare, dopodiché tutti i conigli sono stati alimentati a volontà fino alla macellazione commerciale. Nessun trattamento antibiotico è stato effettuato durante la prova. I coefficienti di digeribilità apparente della dieta da post–svezzamento sono stati misurati su 36 conigli (12 per sistema di alimentazione) da 49 a 53 d di età (ultima settimana di restrizione), mentre i coefficienti di digeribilità della dieta da ingrasso sono stati misurati su 36 conigli (12 per sistema di alimentazione) da 64 a 68 d di età (durante la fase di consumo volontario). Considerato il periodo di realizzazione della prova di digeribilità, quanto il livello nutritivo era pari al 95% del ad libitum, solo la digeribilità della proteina grezza è stata aumentata (P<0,001) nei gruppi razionati. Durante il secondo periodo, nessun effetto residuo del precedente trattamento di restrizione è stato osservato sulla digeribilità della dieta. Nell'intero periodo di prova, mortalità, morbilità e rischio sanitario hanno raggiunto rispettivamente 12,7%, 11,3% e 24,0% in media. Mortalità e rischio sanitario sono stati significativamente (P<0,05) inferiori nei conigli razionati rispetto a quelli alimentati ad libitum ( 12,0 punti percentuali), in particolare quando è stato applicato il sistema progressivo ( 14,2 punti percentuali). Nelle prime tre settimane, il livello di restrizione è stato pari al 91% nel gruppo D e al 93% nel gruppo W; l’accrescimento giornaliero è diminuito in entrambi i gruppi razionati ( 7,5% rispetto al gruppo AL) mentre l’indice di conversione non è stato modificato dal sistema di alimentazione. Nel secondo periodo, solo il gruppo W ha mostrato consumi (+4,2%) e accrescimenti (+14,2%) superiori e migliori indici di conversione ( 3,2%) rispetto al gruppo AL. Il peso vivo finale (2748 g in media), l’indice di conversione (3,07), la resa di macellazione (59,8%) e le caratteristiche della carcassa non sono stati influenzati dal trattamento alimentare. L’escrezione giornaliera di azoto è stata ridotta ( 0.08 g/d per coniglio; P<0.05) nel gruppo D. L’aumento dell’età di macellazione da 73 a 80 d di età ha significativamente aumentato pesi vivi finali (+7,5%; P<0.001) e consumi (+4 g/d; P<0.05); ha ridotto gli accrescimenti ( 3,1 g/d; P<0.001) e peggiorato gli indici di conversione (2,92 vs. 3,22; P<0.001) degli animali. Le caratteristiche della carcassa sono state fortemente (P<0.01) modificate ritardando la macellazione di una settimana: il peso medio delle carcasse è aumentato (da 1563 g a 1705 g) così come la resa di macellazione (da 59,3% a 60,5%), l’adiposità e la muscolosità, mentre l’incidenza dell’intestino pieno è diminuita ( 0,7 punti percentuali). L’escrezione di azoto è aumentata con l’età di macellazione (+0.21 g/d per coniglio). In conclusione, la restrizione alimentare ha migliorato lo stato d salute senza compromettere le performance produttive e le caratteristiche della carcassa. La curva di razionamento progressiva ha rispecchiato in modo migliore il comportamento alimentare dei conigli rispetto alla curva scalare, permettendo di ottenere un livello alimentare in linea con quello atteso. Tuttavia, l’applicazione di questo tipo di programmi di razionamento alimentare appare difficile nelle aziende commerciali in quanto richiede molto tempo e lavoro quando non sono presenti sistemi di alimentazione automatici e potrebbe non essere adeguato per conigli allevati in colonia. L’aumento dell’età di macellazione ha incrementato la resa in carcassa, ma ha peggiorato la conversione alimentare ed aumentato l’escrezione di azoto. Secondo contributo: Restrizione alimentare basata sul tempo e composizione del gruppo in base al sesso: effetti su prestazioni produttive, comportamento alimentare e qualità della carne in conigli in accrescimento L’effetto del sistema alimentare (AL: ad libitum vs. R: razionamento) e della composizione del gruppo in base al sesso (X: sole femmine vs. Y: soli maschi vs. Z: sessi misti) su prestazioni produttive, comportamento alimentare, risultati di macellazione e qualità della carne è stato valutato su 288 conigli ibridi (144 femmine e 144 maschi), allevati dallo svezzamento (33 d di età) alla macellazione (75 d) in 18 recinti collettivi (1 m2; 16 animali per recinto). La restrizione basata sul tempo è stata realizzata aumentando il tempo di accesso alle mangiatoie (principalmente durante le ore di buio) in modo graduale (+1 h ogni 3–4 d) da 10 h/d a 16 h/d nelle prime tre settimane. Dopodiché, il tempo di alimentazione è stato aumentato gradualmente (+1 h/d) fino al raggiungimento del libero accesso al cibo. Durante le prime tre settimane, è stato ottenuto un livello di restrizione mediamente pari al 95% dell’ingestione ad libitum. Nel primo periodo di prova, il consumo è diminuito (128 g/d vs. 122 g/d; P<0,01) e l’indice di conversione migliorato (2,40 vs. 2,29; P<0,001) nei conigli razionati rispetto a quelli alimentati a volontà. Nel secondo periodo di prova, i conigli razionati hanno mostrato un peggiore indice di conversione (2.70 vs. 2.83; P<0,001) rispetto i conigli AL. Nell'intero periodo, le prestazioni produttive non sono state influenzate dal sistema alimentare. Diversamente, la restrizione ha fortemente modificato il comportamento alimentare dei conigli R, che mostravano un consumo medio orario superiore rispetto ai conigli AL per tutto il periodo di accesso all'alimento. Tuttavia, una volta raggiunto il libero accesso alle mangiatoie, nell'arco di pochi giorni, i conigli R hanno adottato un comportamento alimentare simile a quello degli animali sempre alimentati a volontà. Il razionamento non ha modificato il peso di macellazione (2860 g in media), la resa di macellazione (61,0%) e la qualità della carne dei conigli. Il sesso degli animali non ha influenzato le prestazioni produttive nel primo periodo, mentre nel secondo periodo i recinti con sole femmine o a sessi misti hanno mostrato accrescimenti superiori rispetto a quelli di soli maschi (47,0 g/d vs. 43,8 g/d vs. 46,1 g/d per i gruppi X, Y e Z rispettivamente; P<0,01). Allo stesso tempo, l’indice di conversione è diminuito nei recinti X e Z rispetto ai recinti Y (3,66 vs. 3,91 vs. 3,72; P<0,01). Considerando l’intero periodo, accrescimenti, consumi ed indici di conversione non sono cambiati in funzione della composizione del gruppo e tutti gli animali hanno raggiunti pesi vivi simili alla fine della prova. Le perdite di trasporto sono risultate superiori nei gruppi X rispetto ai gruppi Y e Z (3,00% vs. 2,45% vs. 2,80%; P<0,01), mentre la resa di macellazione (60,2% vs. 61,8% vs. 61,0%; P<0,001) e l’incidenza della testa (7,41% vs. 7,65% vs. 7,60%; P<0,05) sono risultate più alte nei maschi. Il pH della carne, le perdite di scongelamento e lo sforzo di taglio misurati sul muscolo l. lumborum sono state significativamente (0,05