221 research outputs found
Effect of feeding programme on growth and body balance of meat rabbits
No full textTwo feeding systems (L, ad libitum vs. R, feed restriction) were combined with three feeding plans (HH, MM, MH) to evaluate the effects on performance, slaughter results and nitrogen balance of 300 commercial crossbred rabbits kept individually from weaning to slaughter (34-70 d of age). Feed restriction ranged from 80% to 100% of ad libitum intake from the beginning of the trial until the end of the 3rd week. The three feeding plans were: 1) HH, H diet with high digestible energy content, 11.1 MJ DE/kg, during the whole trial; 2) MM, M diet with moderate DE, 10.6 MJ/kg, during the whole trial; 3) MH, M diet during the first three weeks and H diet during the last two weeks. Feed restriction did not affect health status, nutrient digestibility, growth rate and slaughter results, but improved feed conversion (2.96 vs. 2.89 in L and R rabbits, respectively; P<0.01) and reduced N excretion (2.15 vs. 2.07 g excreted N/d, in L and R rabbits; P<0.05). At the end of the first period (55 d), R rabbits showed lower empty body protein, lipid, and gross energy gains than L rabbits, but differences disappeared within the end of the trial. The high- energy feeding plan (HH) improved feed conversion (2.89 vs. 2.93 and 2.97 for HH, MH and MM, respectively; P<0.05), but increased excreted N (2.17 and 2.12 vs. 2.03 g/d; P<0.001) because of the higher DP/DE ratio of H diet. In conclusion, a moderate feed restriction during post weaning improved feed conversion and reduced N excretion without negative effects on growth or slaughter results. Besides, N excretion was confirmed to depend largely on dietary nitrogen content
The path of a scholar
No full text“The path of a scholar” is the introduction to Production, Distribution and Trade: Alternative Perspectives, a volume of essays in honour of Sergio Parrinello (edited by Adriano Birolo, Duncan Foley, Heinz Kurz, Bertram Schefold and Ian Steedman, published by Routledge, 2010). The author traces out the scientific career of Sergio Parrinello in context of the italian market for economists of the sixties and seventies of the twentieth century and critically discusses his most significant works, specially those have resulted as seminal contributions for the later development of the neo-Ricardian theory. This discussion inevitably evolves in a tentative appraisal of the meaning of the neo-Ricardian theory in the recent history of political economy.neo-Ricardian; capital controversy; history of political economy
The path of a scholar
No full text“The path of a scholar” is the introduction to Production, Distribution and Trade: Alternative Perspectives, a volume of essays in honour of Sergio Parrinello (edited by Adriano Birolo, Duncan Foley, Heinz Kurz, Bertram Schefold and Ian Steedman, published by Routledge, 2010).
The author traces out the scientific career of Sergio Parrinello in context of the italian market for economists of the sixties and seventies of the twentieth century and critically discusses his most significant works, specially those have resulted as seminal contributions for the later development of the neo-Ricardian theory. This discussion inevitably evolves in a tentative appraisal of the meaning of the neo-Ricardian theory in the recent history of political economy
A RAMAN/SANS/XRD STUDY ON THE STRUCTURE-PROPERTY RELATIONSHIP OF OUTDOOR AND INDOOR ROMAN WALL PAINTINGS
No full textDetermination of the chemical composition of different parts of the wall paintings (pigments, mortars and binders) allows extracting information about technology of preparation of the artefact. Herein we present a multimethodological characterization of wall paintings from a Roman Archeological sites from Cuma, focusing on differences between indoor (domus) and outdoor (Temple) fabrication. Both pigments, binders and mortars were studied via a combination of destructive/microdestructutive (mass spectrometry, ionic chromatography, ICP-based techniques) and non-destructive (Raman microscopy, X-ray diffraction and SANS) methodologies. Particularly, the systematic presence of dolomite only in temple mortars suggests an intentional use of such limestone for outdoor fabrication. Differences between temple and domus extends also to binder composition: proteinaceous binders in domus (possibly egg [3] and animal glue), whereas in TCP no protein was detected but some fat acids (probably from animal fat). Ultimately, the multimethodological study allowed an overall picture of the components and technology of the paintings from fabrications with different use, proposing distinct engineering choices for indoor and outdoor walls.
References
[1] Cartechini L., Pucci P., Sgamellotti A., Marino G., Birolo L., “Proteomic strategies for the identification of proteinaceous binders in paintings” Analytical & Bioanalytical Chemistry 395(7), 2009, 2269-2280.
[2] Gelzo M., Grimaldi M., Vergara A., Severino V., Chambery A., Dello Russo A., Piccioli C., Corso G,. Arcari P. "Comparison of binder composition in Pompeian wall painting styles from Insula Occidentalis" Chemistry Central J. 8(65), 2014, 1-10.
[3] Vinciguerra R, Galano E, Vallone F, Greco G, Vergara A, Bonaduce I, Marino G, Pucci P, Amoresano A, Birolo L, “Deglycosylation Step to Improve the Identification of Egg Proteins in Art Samples”
Analytical Chemistry 87 (20), 2015, 10178-10182.
Acknowledgements
This work was financially supported by Distretto ad Alta Tecnologia dei Beni Culturali (DATABENC scarl), progetto SNECS. “Soprintendenza Speciale per i Beni Archeologici di Napoli e Pompei” – Ufficio Archeologico di Cuma - Dr Paolo Caputo is also acknowledged
Effect of sex and slaughter age on carcass and meat quality of brown hares (L. europaeus)
No full textThe present study aimed at evaluating slaughter results, carcass traits and meat quality in 48 farmed brown hares (L. europaeus) of both sexes slaughtered at two ages (sub-adult hares, on average 73 d of age, vs. adult reproducing hares, on average 17 months) in a commercial slaughterhouse and then dissected following standardized procedures for rabbits. At slaughter, the females were heavier than the males (2783 vs. 2629 g; P<0.05), showed higher full gut incidence (13.7 vs. 12.9%; P<0.05), lower skin and feet incidence (13.3 vs. 14.0%; P<0.01), and lower dressing percentage (66.7 vs. 67.6%; P=0.06). The carcasses of females had lower dissectible fat (1.34 vs. 2.17%; P<0.05) and higher proportion of both l. lumborum (14.3 vs. 13.8%; P<0.05) and hind legs (37.2 vs. 36.4%; P=0.06). When age increased, slaughter live weight (2022 to 3391 g) and carcass weight increased (P<0.001), but dressing percentage did not vary (67.2% on average); the full gut incidence decreased (14.5 to 12.1%; P<0.001), whereas skin and feet proportion increased (12.9 to 14.5%; P<0.001). When age increased, head, liver and thoracic organs proportions decreased (P<0.001); dissectible fat (1.34 to 2.17%; P<0.05) and l. lumborum (13.5 to 14.5%; P<0.001) increased; moreover, hind legs proportion decreased (37.3 to 36.3%; P=0.01) but the muscle to bone ratio of hind legs increased (5.11 to 6.23; P<0.001). Meat quality did not vary with gender, whereas sub-adult animals significantly differed (P<0.001) from adults, showing lower meat pH, higher lightness index, higher redness index for l. lumborum (3.03 to 1.46) and lower redness index for b. femoris (4.07 to 5.76); besides they had higher meat thawing losses and lower shear force measured on the hind leg (2.97 to 4.02 kg/g; P<0.001). In conclusions, hare slaughter and carcass traits differed according to both sex and age, whereas meat quality was affected only by age
Effects of the inclusion of Hermetia illucens meal in diets for rainbow trout (Oncorhynchus mykiss) reared in a low-tech aquaponic system
No full textThe study evaluated the effects of the partial substitution of fish meal (FM) with partially defatted Hermetia illucens (HI) meal on growth, gut morphology and fillet quality of rainbow trout reared in a low-tech aquaponic system. A total of 173 rainbow trout (initial body weight: 156 g ± 39.8 g) were distributed into nine experimental aquaponic units (3 tanks per treatment, initial tank biomass 5.74 ± 0.44 kg m−3) and fed during 76 days with three diets containing 0%, 6.3% and 12.5% HI meal and 20%, 15% and 10% FM, respectively. Therefore, HI meal replaced 0% (HI0, control diet), 25% (HI25), or 50% (HI50) of FM, respectively. During the trial, water quality was not affected by dietary treatment: temperature averaged 19.4 °C (13.8 − 23.7 °C), dissolved oxygen 8.0 mg L−1 (6.08 − 10.2 mg L−1), pH 7.4 (6.4 − 8.5), and total ammonia nitrogen 0.13 mg L−1 (0 − 0.36 mg L−1), while daily water losses due to plant evapotranspiration averaged 1.31% d−1. At the end of the trial, trout mortality was low (2.9%) and not affected by dietary treatment. The specific growth rate was lower in fish fed HI50 diet compared to those fed HI0 and HI25 diets after 26 days (1.07% d−1 vs. 1.22% d−1; p < .001) and at the end of the trial (0.81% d−1 vs. 0.88% d−1; p < .05). However, the dietary inclusion of HI did not affect feed conversion ratio (on average 1.53), final weight (303 g), fish condition factor (1.40), viscerosomatic index (10.9%) and hepatosomatic index (1.22%). Histological analyses of the anterior gut showed no significant differences in villi height (503 μm) whereas the density of goblet cells was higher in HI50 than in HI0 trout (+11%; p < .05). Regarding fish quality, fillet redness (a*) and yellowness (b*) were lower in HI50 than in HI0 treatments (−58% and −19%, respectively; p < .001). Fillet proximate composition, total saturated, monounsaturated and polyunsaturated fatty acids, eicosapentaenoic acid and docosahexaenoic acid were not affected by diets, whereas the content of C12:0 and C14:0 increased with HI dietary inclusion and the index of atherogenicity was higher (+6%; p < .05) in HI50 treatment than in HI0 and HI25 ones. In conclusion, the rearing of rainbow trout was successful in the tested aquaponic system. Fish growth, health and fillet quality were not affected when HI meal replaced 25% FM, whereas at 50% replacement rate some effects on gut histology and fillet colour and nutritional characteristics were detected, which deserve further investigations to be elucidated
Role of feed restriction programs on enhancing gut health, feed efficiency and meat quality in growing rabbits
No full textThe 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 (0.05<P<0.01) lower in Y and Z rabbits compared to X ones. The frequency of injuries increased in pens Y, with only males, and Z, mixed–sexes (5.2% vs. 18.3% and 13.3%; P<0.05). In conclusion, growth performance and meat quality were not significantly affected by the feeding system. The progressive increase of the access time to the feeders from 10 to 16 h/d in the first three weeks did not allow to control accurately the feed restriction level because rabbits adjusted very quickly their ingestion capability. Growth performance, slaughter traits and meat quality were not affected by the sex–group composition. Housing animals in groups of only males increased the risks of aggressiveness.
Third contribution. Effect of the feeding program and group size on growth performance, health status and meat quality in growing rabbits
The effect of the feeding program (AL: ad libitum vs. R: feed restriction) and the group size (8, 16 or 32 rabbits per pen) on growth performance, health status, carcass traits and meat quality was evaluated on 320 crossbred rabbits (160 females and 160 males) reared from weaning (31 d of age) to slaughter (73 d) in 20 open–top pens with different group size (8, 16 or 32 animals) at the same stocking density (16 animals/m2).
Feed restriction provided a progressive decrease of the access time to the feeders during the first week (from 14 h/d to 8 h/d), a stable time of 8 h/d in the second week and a progressive increase (+1 h/d) during the third and fourth week (re–feeding phase), thus achieving a restriction level equal to 85% of ad libitum. Throughout the last two weeks, all rabbits had free access to the feeders.
Feed restriction significantly (P<0.001) reduced feed intake ( 15%) and feed conversion ( 12%) in the first three–week period. During the last three–week period, the previously restricted rabbits showed higher daily growth rate compared to the AL ones (47.2 g/d vs. 48.8 g/d; P<0.05), whereas feed intake and feed conversion did not differ between groups. In the whole period, feed conversion was significantly lower in R group compared to AL group (3.05 vs. 2.93; P<0.001). Digestive troubles appeared before in AL rabbits, but morbidity soon raised in R group during the re–feeding phase. At the end of the trial, mortality rate tended to be higher in the restricted rabbits (6.3% vs. 11.9%; P<0.10). Slaughter weight (2734 g), dressing percentage (61.3%), carcass traits and meat quality were not affected by the feeding program.
No significant difference in growth performance, slaughter results and meat quality was observed according to the group size. Nevertheless, rabbits housed in larger groups were subjected to increased sanitary risk (6.3% vs. 14.8% and 18.0% for groups with 8, 16 and 32 rabbits/pen, respectively; P<0.05).
In conclusion, the application of a feed restriction program characterized by a progressive reduction of the access time to the feed during the first week, a constant phase in the second week, and a progressive increase during the third and fourth week allowed to obtain the expected restriction level in the first trial period (85% of ad libitum). Feed restriction significantly improved feed conversion without affecting final live weight, slaughter traits and meat quality. However, even if a progressive re–feeding phase was performed, morbidity and mortality rate increased in the previously restricted rabbits during the second trial period. Housing animals in large groups impaired sanitary conditions.
Fourth contribution. Effect of different rationing and re–feeding programs on growth performance, digestive physiology, health status, slaughter traits and meat quality in group–housed rabbits
The effects of feeding system (ad libitum vs. restriction) and restriction method (diurnal vs. nocturnal access to feed) were evaluated on growth performance, digestive physiology, health status, slaughter traits and meat quality of 400 growing rabbits housed from weaning (28 d of age) to slaughter (70 d) in collective pens of 8 animals (stocking density of 16 animals/m2). Moreover, the effects of re–feeding speed (fast: +4 h/d vs. slow: +1/+2 h/d of access to feed) and re–feeding level (complete: up to 24 h/d vs. incomplete: up to 12 h/d of access to feed) were also assessed. The following groups were formed: ad libitum (AL); diurnal rationing with fast and complete re–feeding (DF); nocturnal rationing with fast and complete re–feeding (NF); nocturnal rationing with slow and complete re–feeding (NS) and nocturnal rationing with very slow and incomplete re–feeding (NI).
The rationing programs previewed a first week of decreasing access time to feed until 9 h/d; a second week of stable daily access time (8 h/day) and a re–feeding period starting from the beginning of the third week.
The diurnal access to the feed led to an initial restriction level more severe than that obtained with the nocturnal rationing programs, but after one week of adaptation DF group reached the feed intake of nocturnal restricted groups (N groups). Feeding time reduction (until 8 h/d) in the first two weeks decreased feed intake ( 24% of ad libitum) and weight gain ( 7% with respect to the AL group) of restricted rabbits leading to a significantly lower live weight at the end of the third week (1761 g vs. 1671 g for AL and restricted rabbits, respectively; P<0.001). However, restricted rabbits showed a feed conversion significantly lower compared to that of ad libitum ones (2.11 vs. 1.95; P<0.001) in the first period. Indeed, during the second week, the feed restriction significantly (0.01<P<0.001) enhanced the digestibility of dry matter (+3.5%) and most of nutrients compared to the ad libitum system, irrespective of the feed restriction method. At 43 d of age, the pH of the caecal content was lower in DF and NF rabbits compared to AL ones (5.46 vs. 5.34 on average; P<0.01). Accordingly, the total production of volatile fatty acids (VFA) increased in DF and NF groups with respect to AL group (+15% on average), while the N–ammonia decreased in restricted groups ( 29% on average). In the second rearing period, with the re–feeding phase, the weight gain was higher (P<0.001) in previously restricted rabbits compared to AL ones (47.1 g/d vs. 51.1 g/d) because of the increase (P<0.001) in feed intake (157 g/d vs.165 g/d). The NI group, characterized by an incomplete re–feeding, showed higher feed efficiency with respect to the groups submitted to complete re–feeding curves (P<0.05). Indeed, at the end of re–feeding (51 d of age), the digestibility of gross energy and crude protein of fattening diet was higher in NI group compared to the fast re–fed groups (0.05<P<0.01). At the same age, the total VFA production was still higher in the restricted groups compared to AL one (+19% on average; P<0.001) and increased with the decrease of re–feeding speed (P<0.01).
Animal health status was not affected either by the feeding system (ad libitum or feed restriction) or by the rationing method (diurnal or nocturnal) or by the re–feeding program (fast, slow or incomplete).
Slaughter weight (2607 g on average), dressing percentage (60.2% on average), carcass traits and meat quality did not change according to the feeding program.
In conclusion, a nocturnal rationing program performed by decreasing gradually the access time to feed in the first week of post–weaning and increasing slowly the feeding time up to 12 h/d at the fourth week onwards represented the best strategy to optimize feed efficiency in growing rabbits without impairing health status, growth performance, slaughter traits and carcass and meat quality.
The restriction levels applied in our trials (85–90% of ad libitum during the first three weeks after weaning) have been set to find a balance between the positive effects on gut health and the negative impact on the growth performance of rabbits. Generally, a more severe feed restriction (≤80% of ad libitum) applied during post–weaning allows to obtain a relevant enhancement of animal health status, but it may compromise the overall productive performance of rabbits by decreasing final live weight, slaughter yield and impairing carcass traits. In the first contribution, with rabbits housed individually, the total mortality rate was significantly reduced by applying a moderate restriction level (90% of ad libitum) during post–weaning especially when a progressive and gradual feed restriction curve was adopted. In this regards, a slight feed restriction may exert a protective effect on gut health in conditions of limited contacts among animals. Nonetheless, in the third contribution, a strict rationing program preserved the digestive health of rabbits housed collectively in the first two weeks, but its positive effect disappeared when the animals started the re–feeding phase. Feed restriction can lead to a relevant increase of mortality in previously restricted rabbits during the last weeks of fattening, thus increasing the economic impact of animal losses. Indeed, in the fourth contribution neither the application of a very slow and even incomplete (12 h/d) re–feeding programs was effective in reducing the incidence of digestive troubles once an antibiotic-free diet was supplied.
In the first two trials, no differences in terms of feed efficiency and growth performance were detected among restricted and ad libitum groups. On the other hand, in the third and fourth contributions, with the implementation of more severe feed restrictions, daily growth decreased in the first period, but restricted rabbits reached live weights similar to those of AL ones at the end of trial, thanks to the occurrence of a compensatory growth during the re–feeding period. Moreover, a significant reduction of feed conversion was detected in restricted groups especially when an incomplete re–feeding was used. The rationing programs did not affected slaughter results, carcass traits and meat quality: the restriction levels tested and the length of re–feeding phase could explain these results. The improvement of feed efficiency in restricted rabbits could be related to the increase in diet digestibility. However, this effect occurred only during the restriction phase. Indeed, an incomplete re–feeding until the end of trial allowed to maintain a higher diet digestibility compared to the complete re–feeding techniques.
The feeding behaviour of rabbits greatly changed when the animals were subjected to limited access time to the feeders. However, in our conditions, the rabbits adopted a feeding behaviour similar to that of rabbits always fed ad libitum within few days after reaching the free access to the feed. In the fourth contribution, a diurnal access to the feed involved a deeper change in the feeding behaviour of rabbits, which need approximately one week to reach the intake level of rabbits fed during the night.
In conclusion, our results confirm the possibility to apply feed restriction programs in the Italian production system with the main objective of enhance feed efficiency. The control of digestive diseases still appear difficult to be achieved and the relationship between feed restriction and gut health needs further investigations. A time–based feed restriction, characterized by a feeding time shorter than 10 h/d during the first three weeks after weaning and followed by an incomplete re–feeding (up to 12 h/d) could be the most suitable technique to be used in field conditions and in group–housed rabbits. Further investigations may be also carried out to prove a possible synergistic effect by combining feed restriction programs with different diet compositions
STRUCTURAL CHARACTERISATION OF M-PARTLY FOLDED INTERMEDIATES OF WILD-TYPE AND P138A ECASPAT
No full textSTRUCTURAL CHARACTERISATION OF M-PARTLY FOLDED INTERMEDIATES OF WILD-TYPE AND P138A ECASPAT
No full textA proteomic approach to identify ubiquitinated proteins in a macrophage cell-free system
No full text- …
