Effects of floor type, stocking density, slaughter age and gender on productive and qualitative traits of rabbits reared in collective pens

At 34 d of age, 376 crossbred rabbits of both sexes were housed in 16 open-top collective pens (1.68 m2) according to a 2 72 72 factorial arrangement with two types of pen floor (wooden v. plastic slatted), two stocking densities (12 v. 16 animals/m2), and two slaughter ages (76 v. 83 d). The rabbits were examined for growth performance, slaughter results, and meat quality. The effect of gender was also examined. The percentage of rabbits with wounds due to aggression varied with stocking density (8.2% v. 26.2% for 12 v. 16 animals/m2; P 64 0.001), slaughter age (15.0% v. 22.0% at 76 v. 83 d; P 64 0.10), and gender (11.3% v. 25.8% for females v. males; P 64 0.001). Rearing rabbits on a plastic rather than a wooden slatted floor promoted slaughter weight (2795 g v. 2567 g; P 64 0.001), dressing percentage (61.4% v. 60.9%; P 64 0.01), dissectible fat (2.4% v. 2.0%; P 64 0.01), and hind leg muscle-to-bone ratio (5.81 v. 5.35; P 64 0.001). Increased stocking density impaired daily growth (38.5 g/d v. 35.9 g/d; P 64 0.05) and feed intake (140 g/d v. 134 g/d; P 64 0.01) during the second period (55 d to slaughter) and decreased slaughter weight (2725 g v. 2637 g; P 64 0.01). At the older slaughter age, the feed conversion ratio was impaired (2.98 v. 3.18; P 64 0.001); the slaughter weight (2574 g v. 2788 g; P 64 0.001), dissectible fat (2.0% v. 2.4%; P 64 0.01), and hind leg muscle to bone ratio (5.41 v. 5.75; P 64 0.01) increased; meat thawing losses, cooking losses, and shear force decreased (P 64 0.05). The main differences between the females and males were found in the slaughter for transport losses (2.6% v. 2.2%; P 64 0.01) and l. lumborum proportions (13.0% v. 12.4%; P 64 0.01). In conclusion, the growth performance of pen-housed rabbits was largely determined by the type of floor and less affected by stocking density. The meat quality depended on ontogenetic factors, such as slaughter age and gender, and not on housing conditions. The differences in the percentages of wounded animals due to experimental factors deserve further investigation from the perspective of animal welfare issues

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

Effect of feed restriction and feeding plans on performance, slaughter traits and body composition of growing rabbits

[EN] Two feeding systems (L, ad libitum vs. R, feed restriction) were combined with 3 feeding plans (MM, MH, HH) to evaluate the effects on performance, slaughter results, body composition and nitrogen balance of 300 commercial crossbred rabbits kept individually from weaning to slaughter (34-70 d of age). The R rabbits were fed from 80% (first days on trial) to 100% (end of 3rd wk) of ad libitum intake, whereafter R rabbits had free access to feed. The 3 feeding plans were: MM plan, M diet with moderate digestible energy (DE) content, 10.6 MJ/kg, throughout the trial; HH plan, H diet with high DE content, 11.1 MJ/kg, throughout the trial; MH plan, M diet for the first 3 wk and H diet for the last 2 wk. Feed restriction did not affect nutrient digestibility, growth rate on the whole trial 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 (2.16 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 HH plan improved feed conversion (2.97 vs. 2.89 for MM vs. HH; P<0.05), but increased excreted N (2.03 vs. 2.17 g/d; P<0.001) in comparison with the MM plan due to the higher digestible protein/DE ratio of H diet, whereas the MH plan showed intermediate results. In conclusion, a moderate feed restriction during post weaning improved feed conversion and reduced N excretion without negative effects on growth or slaughter results. Moreover, N excretion was confirmed to depend largely on dietary nitrogen content.This study was funded by the Ministero dell’Istruzione dell’Università e della Ricerca (Project COD.60A08–7188/12).Birolo, M.; Trocino, A.; Tazzoli, M.; Xiccato, G. (2017). Effect of feed restriction and feeding plans on performance, slaughter traits and body composition of growing rabbits. World Rabbit Science. 25(2):113-122. https://doi.org/10.4995/wrs.2017.6748SWORD113122252Blas, C. de, & Mateos, G. G. (s. f.). Feed formulation. Nutrition of the rabbit, 222-232. doi:10.1079/9781845936693.0222Di Meo C., Bovera F., Marono S., Vella N., Nizza A. 2007. Effect of feed restriction on performance and feed digestibility in rabbits. It. J. Anim. Sci., 6: 765-767.ERM/AB–DLO. 1999. Establishment of Criteria for the assessment of the nitrogen content of animal manures, European Commission, Final Report, Luxembourg.Fernández Carmona J., Pascual J.J., Cervera C. 2000. The use of fats in rabbit diets. In: Proc. 7th World Rabbit Congress, 5-7 July, 2000, Valencia, Spain. World Rabbit Sci., 8, suppl. 1, vol. C, 29-59.Gidenne T., Aubert C., Drouilhet L., Garreau H. 2013a. Feed efficiency in rabbit breeding: technico-economical and environmental impacts. In: Proc. 15èmes Journ. Rech. Cunicole, 26-27 November, 2013, Le Mans, France, 1-13.Marlier D., Dewree R., Delleur V., Licois D., Lassence C., Poulipoulis A., Vindevogel H. 2003. A review of the major causes of digestive disorders in the European rabbit. Ann. Med. Vet., 147: 385-392.Mertens D.R. 2002. Gravimetric determination of amylase-treated neutral detergent fiber in feeds with refluxing in beakers or crucibles: collaborative study. J. AOAC Int., 85: 1217-1240.XICCATO, G. (2010). FEEDING AND MEAT QUALITY IN RABBITS: A REVIEW. World Rabbit Science, 7(2). doi:10.4995/wrs.1999.383Xiccato G., Cinetto M., Dalle Zotte A. 1992. Effetto del livello nutritivo e della categoria di conigli sulla digeribilità degli alimenti e sul bilancio azotato. Zoot. Nutr. Anim., 18: 35-43.Xiccato G., Trocino A., Sartori A., Queaque P.I. 2003. Effect of weaning diet and weaning age on growth, body composition and caecal fermentation of young rabbits. Anim. Sci., 77: 101-111. https://doi.org/10.1017/S135772980005370

Increasing Dietary Energy with Starch and Soluble Fibre and Reducing ADF at Different Protein Levels for Growing Rabbits

The effect of increasing dietary energy by increasing both starch (14% to 20%) and soluble fibre (9.6% to 11.6%) and decreasing ADF content (21% to 13%) at two crude protein levels (14% and 15%) was assessed on health, growth performance, caecal fermentative activity, gut mucosa traits, and carcass and meat quality of growing rabbits reared from 34 to 76 days of age. At weaning, 306 rabbits were divided into six groups and fed ad libitum six diets formulated according to a bi-factorial arrangement with 3 (starch+soluble fibre)/ADF ratio (L=1.2; M=1.8; H=2.8) x 2 protein levels. The contemporary increase of dietary starch and soluble fibre and the reduction of ADF linearly increased the digestibility of dry matter, energy and all nutrients, decreased feed intake and improved feed conversion (3.65 to 2.76 in rabbits fed diets L and H; P<0.001); it increased morbidity (P=0.09) but did not affect mortality due to epizootic rabbit enteropathy; at caecum, VFA production raised (52.1 to 61.9 mmol/L) and pH (5.90 to 5.67) and N ammonia lowered (4.85 to 1.93 mmol/L); the villi/crypts ratio (4.42 vs. 3.81 and 3.95 in rabbits fed diets L, M and H) decreased in a non linear mode. The decrease of the protein level did not affect growth performance, but nearly halved mortality (28.9% vs. 16.3%; P=0.01) and increased caecal pH (5.70 to 5.87; P=0.05). Weak effects of the dietary treatments were measured on carcass traits and meat quality

Feeding strategies to improve health status and feed efficiency in growing rabbits

Epizootic Rabbit Enteropathy (ERE) has become the main cause of losses in intensive rabbit farms: it is typical of post weaning period and can be described as a severe form of mucoid enteropathy, complicated by secondary etiologic agents. The main solution to ERE are antibiotics, but the European rules limit the possibility of using them in preventive treatments. Moreover, due to the fast evolution of the disease, once ERE occurs and is recognized, the therapeutic use of antibiotics may often not be applied on time to control economic losses. In addition, the cost of the therapy has an important impact in rabbit production costs. In the last decade, the studies intended to specify the nutritional requirements and feeding strategies in rabbits during weaning and post weaning with special emphasis on the possibility of reducing the damages caused by ERE. With regards to nutrients, both experimental studies and field results push towards the reduction of the use of high insoluble fibre diets in growing rabbits, because they greatly limit growth performance, impair feed conversion and increase nitrogen excretion while sometimes do not avoid the need of using prophylactic and therapeutic drugs. The negative role of starch on the occurrence of digestive diseases has been somewhat put under discussion, whereas a positive effect of the most soluble fibre fractions has been outlines on both health and performance of growing rabbits when used in substitution of insoluble fibre or starch. Finally, both lack and excess of crude protein are critically considered because of their negative effects on caecal fermentative activity, microflora composition and lastly on rabbit health. With regards to feeding management, feed restriction programs may be used also with some advantages on global farm efficiency as they increase diet utilization, modify the partition of body energy retention as protein instead of fat, and may reduce mortality and morbidity due to digestive problems. With these programs, especially in the early period of breeding, growth is controlled and limited during the restriction period but the compensatory growth during the following period of re alimentation allows animals to recovery productive performance at the end of the rearing period. From the end of the ‘90s, feed restriction has been widely used in some European Countries (especially France) during the post weaning period to control the mortality due to digestive disorders. Positive effects of this technique have been outlined since the spread out of ERE in terms both of a better control of the disease and improvement of the global feed conversion. The general objective of the present thesis was the development of nutritional strategies for improving feed efficiency and health status of growing rabbits. This goal was pursued by means of experimental activities with the specific objectives of: i) defining requirements of soluble fibre in relation to dietary insoluble fibre, starch and protein in rabbits during post weaning and fattening (experiments 1 and 2); ii) measuring the effect of the rate and duration of feed restriction compared to an ad libitum feeding, in order to define the most effective restriction technique capable of maximizing performance and controlling digestive problems in growing and fattening rabbits (experiments 3 and 4).L’Enteropatia Epizootica del Coniglio (Epizootic Rabbit Entropathy, ERE) è diventata, negli ultimi decenni, la principale causa di perdite a livello economico negli allevamenti cunicoli europei, con aumento della morbilità e della mortalità traducibili in un importante peggioramento della conversione alimentare a livello aziendale. È una patologia caratteristica del periodo di post svezzamento e può essere descritta come una grave forma di enteropatia mucoide, complicata da affezioni batteriche secondarie che, spesso, ne rendono difficile l’interpretazione dei sintomi e l’attribuzione sicura della malattia (Marlier e coll., 2003; Rosell, 2003). Non essendo stato ancora identificato l’agente eziologico della malattia cui piuttosto si riconosce un carattere multifattoriale, le principali soluzioni adottate fino ad oggi hanno riguardato l’utilizzo di antibiotici in profilassi e meta filassi orientati al controllo di clostridi e coli, ma la vigente normativa comunitaria ne limita l’utilizzo a fini preventivi. Inoltre, a causa della rapida evoluzione della malattia, una volta che l’ERE è stata diagnosticata, l'intervento con antibiotici a scopo terapeutico non sempre è sufficientemente tempestivo da limitare le perdite economiche (Xiccato e coll., 2008). A ciò si aggiunga il costo della terapia antibiotica, che risulta avere un considerevole impatto sui costi di produzione degli allevamenti cunicoli e l’elevata frequenza di scarsa efficacia del trattamento antibiotico dovuta a ceppi di clostridi e coli resistenti. A tal proposito, gli studi effettuati negli ultimi decenni hanno puntato a definire al meglio i fabbisogni nutrizionali degli animali e a sviluppare nuove strategie alimentari soprattutto nelle fasi di svezzamento e post svezzamento in relazione alla possibilità di ridurre le perdite causate dall’ERE. Infatti, la nutrizione gioca un ruolo fondamentale nello sviluppo delle popolazioni microbiche intestinali e nella possibilità che batteri enteropatogeni possano prevalere sulle popolazioni simbionti. In particolare, parlando dei nutrienti della dieta è risaputo come il contenuto ottimale di amido in mangimi per conigli nella fase di svezzamento si attesti attorno al 10 15%, mentre può superare il 15% nelle ultime fasi di ingrasso e finissaggio (De Blas e Mateos, 2010). L'utilizzo di diete ad alto tenore in amido viene spesso associato alla comparsa di disturbi digestivi durante le fasi di svezzamento e post svezzamento (Blas e Gidenne, 2010). Quanto detto trova riscontro nella teoria di Cheeke (1987), secondo la quale diete ricche in amido e povere di fibra aumenterebbero il flusso di amido a livello ciecale, soprattutto negli animali giovani che presentano una scarsa attività delle amilasi intestinali. A livello ciecale, l’amido viene fermentato dai batteri amilolitici, aumenta la produzione di acidi grassi volatili (AGV) provocando un importante riduzione del pH. Queste condizioni risulterebbero favorevoli alla proliferazione di Clostridium spiroforme che, utilizzando il glucosio in eccesso, produrrebbe una tossina iota simile, principale causa di enteriti e diarree. I fabbisogni proteici si attestano attorno al 15 16% di proteina grezza (PG) o al corrispondente 10,5 11% di proteina digeribile (PD). Per quanto riguarda le relazioni intercorrenti tra il livello proteico della dieta e la salute degli animali, la carenza (18%) di PG possono favorire la presenza di problemi digestivi e quindi aumentare la mortalità modificando l’attività fermentativa ciecale e la composizione della microflora intestinale (Maertens e De Groote, 1988; Lebas, 1989; Carabaño e coll., 2008, 2009). Tutte le popolazioni microbiche beneficiano della disponibilità proteica a livello ciecale per il loro sviluppo e la loro proliferazione, ma alcune specie (in particolare E. coli e Clostridia) sembrerebbero maggiormente avvantaggiate da squilibri nell’apporto proteico. Per quanto concerne i fabbisogni delle diverse frazioni fibrose, vengono consigliati quantitativi minimi pari al 5% di ADL e 16 17% di ADF (Gidenne e García, 2006). Bassi livelli di fibra insolubile diminuirebbero la velocità di transito, prolungando la permanenza dell’alimento nel tratto intestinale; questo aumenterebbe la fermentazione delle proteine, con conseguente aumento dell’azoto ammoniacale e del pH ciecale favorendo le disbiosi intestinali (Gidenne, 1996;. Bennegadi e coll., 2000). Anche un eccesso di fibra insolubile, tuttavia, associato ad una carenza di sostanze fermentabili a livello ciecale, promuove lo sviluppo di una microflora patogena nel cieco, in particolare Escherichia coli., come descritto dalla nota teoria di Morisse e coll. (1985). D’altra parte è stato evidenziato un effetto positivo della fibra solubile sullo stato di salute dei conigli soprattutto quando il suo incremento avviene a spese dell’amido in diete con un contenuto di ADF costante (Jehl e Gidenne, 1996; Perez e coll., 2000; Soler e coll., 2004; Xiccato e coll., 2008). In questo caso risultano migliorate le condizioni a livello ciecale con pH più bassi, conseguenza di una maggior produzione di AGV e di una minore concentrazione di azoto ammoniacale. Inoltre, non è modificata la digeribilità della sostanza secca e il contenuto energetico delle diete, pur migliorando considerevolmente la digeribilità delle frazioni fibrose delle diete stesse (Gidenne e Jehl, 1996; Gidenne e Bellier, 2000; Gidenne e Perez, 2000; Xiccato e coll., 2008, 2010; Trocino e coll., 2011). Al fine di controllare i disturbi digestivi si possono utilizzare anche programmi di restrizione alimentare. In particolare essi possono essere utilizzati al fine di migliorare l’efficienza globale dell’allevamento, aumentando l’utilizzazione digestiva della dieta fornita, modificare la composizione corporea in termini energetici, favorendo la deposizione di proteina a scapito di quella di grasso, ed infine ridurre la mortalità e la morbilità in allevamento causate da disturbi digestivi. Mediante l’applicazione di programmi di restrizione alimentare nella prima fase di allevamento, l’accrescimento viene controllato e quindi limitato durante la fase di restrizione ma, l’accrescimento compensativo durante la successiva fase di re alimentazione permette agli animali di recuperare le performance produttive durante la fase finale di allevamento. I primi studi effettuati sui piani di restrizione alimentare nel coniglio valutavano l’effetto di tali piani sulle performance produttive degli animali, sulle caratteristiche della carcassa e sulla qualità della carne. In seguito, il razionamento è stato utilizzato al fine di migliorare l’efficienza alimentare e standardizzare le curve di crescita negli animali con differenti capacità di ingestione. (Ouhayoun e coll., 1986; Ouhayoun, 1989; Cavani e coll., 1991). Dalla fine degli anni ’90, la restrizione alimentare è stata utilizzata soprattutto nel periodo di post svezzamento al fine di controllare i disturbi digestivi. Gli effetti positivi di queste strategie alimentari sono risultati evidenti sull’insorgenza e la diffusione dell’ERE, in quanto hanno un’azione positiva in termini di contenimento della patologia e di migliore indice di conversione globale (Maertens, 1992; Gidenne e coll., 2003; Tudela, 2009). Fatte queste premesse, obiettivo generale della presente Tesi di dottorato è stato lo sviluppo e la messa a punto di strategie nutrizionali per il miglioramento dell’efficienza alimentare e dello stato di salute di conigli in accrescimento. Tale obiettivo è stato perseguito mediante quattro attività sperimentali, in cui si è articolata la presente Tesi di Dottorato, orientate ai seguenti specifici obiettivi: i) definizione dei fabbisogni di fibra solubile in rapporto al contenuto di fibra insolubile, di amido e di proteina in conigli in post svezzamento e ingrasso (contributi sperimentali 1 e 2); ii) valutazione dell’effetto del livello e della durata della restrizione alimentare rispetto ad un’alimentazione ad libitum nell’ottica della massimizzazione delle prestazioni produttive e qualitative e del controllo dei problemi digestivi (contributi sperimentali 3 e 4)

Effect of feed restriction level and period on performance and health of growing rabbits

The present study aimed to evaluate the effect of the level (100%, 90% and 80% of ad libitum) and period (2 and 3 weeks) of post-weaning feed restriction on growth performance and health status of 246 growing rabbits controlled from weaning until commercial slaughter (33-75 d of age). Despite significant effects of restriction program during the restriction period itself and soon after, the differences in final live weights of non-restricted and restricted rabbits were not significant, whereas rabbits submitted to the strongest restriction (80%) still tended to be lighter compared to R90 rabbits (P=0.06). Therefore, daily weight gain from 33 to 75 d of age was lower in R80 compared to R90 rabbits (P=0.04); feed intake was lower in restricted vs. not restricted rabbits and in R80 vs. R90 rabbits. Feed conversion was lower (P=0.04) in restricted rabbits without differences between the two restriction levels (R90 vs. R80). The restriction program, level and period did not affect rabbit health in the entire trial

Effect of feeding programme on performance and health of growing rabbits

The effects of two feeding systems (L, ad libitum vs. R, feed restriction) combined with three diets (HH, a high digestible energy diet, 11.1 MJ DE/kg, during the whole trial vs. MM, a moderate DE diet, 10.7 MJ/kg, during the whole trial vs. MH, a moderate DE diet during the first three weeks and a high DE diet during the last two weeks) were evaluated in 252 commercial crossbred rabbits kept individually from weaning to slaughter (34 to 70 d of age). The restricted rabbits were fed from 85% of the theoretical ad libitum intake at the beginning of the trial to 100% of the ad libitum level at the end of the 3th week. During the first week, growth rate was impaired by feed restriction (53.6 and 46.8 g/d in L and R rabbits, P0.10) and lower growth rate compared to R rabbits (48.2 vs. 51.3 g/d, P=0.05). During the fourth and fifth weeks, neither growth rate nor feed intake differed between the two groups. In the whole trial only feed conversion was improved by feed restriction (2.96 vs. 2.89 in L and R rabbits; P<0.01) and by the high-DE program (2.89 vs. 2.93 and 2.97, for HH, MH and MM groups, respectively; P<0.05). Morbidity was lower in the restricted group (5.5% vs. 2.4% in L and R rabbits; P<0.001) and in HH and MM groups compared to MH group (3.6% and 2.4% vs. 5.9% respectively; P<0.001). In conclusion, feed restriction improved feed efficiency and health, whereas the change from a moderate to a high energy diet during the growing period could impair rabbit health

Feed restriction programs and slaughter age in growing rabbits

The present study aimed at evaluating the effects of the feeding system (AL: ad libitum vs. D: day-by-day restriction vs. W: week-by-week restriction) and the slaughter age (73 vs. 80 d) on health status, growth performance, carcass and meat quality, and material balance of growing rabbits. A total of 300 commercial crossbred rabbits were housed in individual cages from weaning (36 d of age) to slaughter. The feed restriction was based on the administration of a restricted amount of the diet varying from 80% of the ad libitum intake at the beginning of the trial to 100% of the ad libitum intake at the beginning of the 4th week. The restriction level (about 90% on average) was obtained by two restriction curves: a day-by-day curve with small daily increments (+4 g/d; D group) and a week-by-week intake curve with large weekly increments (+23 g/week on average; W group). Mortality was significantly higher in the AL group compared to the daily and weekly restricted groups (20.7% vs. 11.0% and 6.5%; P<0.05). Final live weight (on average 2749 g), feed conversion (3.07), cold dressing percentage (59.9%) and other carcass and meat quality traits were not affected by the feeding system. However, the restricted rabbits evidenced increased empty body fat and energy gains (P<0.01) as a consequence of the compensatory growth during the second half of the trial. The delay of slaughter from 73 to 80 d of age significantly increased final live weight (2,647 vs. 2,847 g; P<0.001), reduced daily weight gain (47.3 vs. 44.3 g/d; P<0.001), increased feed intake, and impaired feed conversion (2.92 vs. 3.22; P<0.001). Besides, lipid and energy body content raised in the older rabbits (P<0.001). No substantial interaction between feeding regime and slaughter age was found. In conclusion, feed restriction improved rabbit health status and did not affect either growth performance or carcass and meat quality, whereas increased the body fat and energy deposition compared to the ad libitum feeding. A progressive day-by-day restriction curve appeared to be less risky and more respectful of the feeding behaviour of growing rabbits in comparison with a discontinuous week-by-week increment of feed administration and permitted to obtain a restriction level nearer to what expected (91% in D group vs. 93% in W group). The increase of slaughter age was much more effective in modifying growth and slaughter performance as well as body composition of rabbits than the feeding system