Different rearing systems for fattening rabbits: Performance and carcass characteristics

Physicochemical properties and sensory profile of some breeds of rabbits in Algeria

The objective of this study was to compare physicochemical traits and sensory profile of meat from rabbits of both sexes belonging to two genotypes, local population and new line (ITELV 2006) which exhibited better characteristics due to its genetic potential. A total of 60 rabbits at 90 days of age were used in the experiment. At slaughter, meat physicochemical and sensory characteristics were measured on Longissimus lumborum muscle. Differences related to genotype were found in most of the physicochemical characteristics studied like Cooking Losses (P < 0.001), Percentage of Released Water (P < 0.001), Myofibril Fragmentation Index (P < 0.001) and a* value (P < 0.001). However, in some of the traits, the differences were related to interaction of sex and genotype (S*G) as in the case of Cooking Losses (P < 0.001) and b* value (P < 0.01). Regarding SDS-PAGE analysis results, the comparison between two breeds has not shown any particular distinction in the myofibrillar and sarcoplasmic protein profiles in relation to the number and the intensity of bands. No significant differences in the sensory characteristics of the meat were noted (P > 0.05). Interestingly, no relevant differences were found between meat from male and female rabbits in all the variables studied (P > 0.05). It was concluded that meat quality was mainly affected by genotype. Thus, the new line exhibited good physicochemical characteristics compared to the local one. This study is the first to analyse and compare the physicochemical and sensory properties of Algerian rabbit meat.

Profile of Nitrogenous compounds and Bacterial proliferation in Rabbit meat stored cold with three types of packaging

Meat is an excellent medium for bacterial growth due to its high water and nutrient content. The nitrogenous compounds (NC) are derived through decarboxylation of amino acids due to microbial enzymes. The objective of this study was to evaluate the concentration of 3 NC and the proliferation of some microorganisms in rabbit meat with three treatments (T) , classified by three types of packaging for 21 days (d) in rabbit meat stored cold. The meat samples were obtained of the Longissimus thoracis et lumborum muscle. Each sample was divided and two groups were formed. The first group was used to measure the physicochemical characteristics of the meat, and the second group was used to quantify NC and bacterial isolation. The pH in the meat decreased from 0 to 21 d in the three T. The brightness (L*) decreased (P<0.05), while the variables a* and b* increased (P<0.05) to 21 d for all groups. Histamine and cadaverine remained low and were similar in the three T (P>0.05). Putrescine (PU) increased (P<0.05) from 7 to 21 d in the Control-Plastic (CP) and Semi-permeable plastic film (SP) groups vs. Vacuum packing (VP). The Enterobacteriaceae remained constant throughout the experimental period in the three T, compared to the aerobic mesophilic, which was higher (P<0.05) until 21 d of the evaluation in CP and SP. The type of packaging and cooling time influenced the concentration of NC. The VP had the lowest level of PU and mesophilic bacteria until 21 d of storage.

Evaluating productive performance, meat quality and oxidation products of Italian White breed rabbits under free-range and cage rearing system

Objective

Free-range systems have been increasingly available to the consumer due to increased demand for more sustainable meat-products. In the current study, the effect of free-range (FR) and cage system (CS) was explored on growth performance, meat quality and oxidation products in Italian White breed rabbits during the growing-fattening phase (5 to 13 weeks of age).

Methods

Forty rabbits were randomly allotted to two treatment groups according to the rearing system, and each treatment group was replicated five times with four subjects in each replicate (20 rabbits per treatment-group). All rabbits fed the same diet as pelleted, and under FR system, no additional feeds were available to animals.

Results

Rearing system had significant effect on rabbit growth performance, where CS group resulted in higher final body weight (p<0.045) and gain (p<0.029) and better feed efficiency (p<0.025) compared to FR rabbits. Most carcass traits were not affected by rearing system; however, a reduction of abdominal fat content (p<0.015) and meat lipids (p<0.034) was observed in FR rabbits. Rearing system had no effects on meat fatty acid profile, whereas meat from FR rabbits resulted less susceptible to lipid and protein oxidation compared to caged animals.

Conclusion

In overall, FR system could be suggested as a substitute for conventional caged system because of FR system preserved rabbit meat from oxidation.

Influence of Stress Assessed through Infrared Thermography and Environmental Parameters on the Performance of Fattening Rabbits

Simple Summary

The aim of this study was to evaluate the impact of stress due to heat (temperature-humidity index; THI) or handling (human restraining), assessed using infrared thermography, on the performance parameters of rabbits of a Spanish Common breed. Thirty-nine rabbits weaned at the age of 28 days were analyzed during a 38-d fattening period at two times of the year: a cold period and a warm period. The rabbits’ stress due to handling was assessed by the temperature difference taken by infrared thermography in the inner ear of the animals, before and after being handled. In general, the productive results were low, since it was an unimproved rustic breed. The animals were more productive in the cold season as the values obtained for daily feed intake (DFI), average daily gain (ADG), total body weight (TBW), total feed intake (TFI) and total weight gain (TWG) were higher then, while the feed conversion ratio (FCR) was higher in the warm season. The greater the stress due to handling, the less efficient the animals were. It was therefore concluded that changes in animal welfare caused by the rabbits’ reactivity to both climatic and individual factors affect animal productivity.

Abstract

Rabbits often experience stress when they perceive certain stimuli, such as handling. The physiological response of animals to stress and temperament is associated with feeding efficiency, with those with the least capacity to react to stress showing the highest performance. The aim of this study was to evaluate the impact of stress due to heat (temperature-humidity index; THI) or handling, assessed using infrared thermography, on the performance parameters of rabbits of a Spanish Common breed. Thirty-nine rabbits were analyzed during a 38-d fattening period at two times of the year: a cold period and a warm period. The rabbits’ stress due to handling was assessed by the temperature difference taken in the inner ear, before and after being handled. The animals were more productive in the cold season. Temperature-humidity index significantly influenced average daily gain (ADG) and daily feed intake (DFI). Rabbits with higher levels of stress showed higher ADG, DFI and feed conversion ratio (FCR) values. The greater the stress due to handling, the less efficient the animals were. FCR increased with higher THI. It was concluded that changes in animal welfare caused by the rabbits’ reactivity to both climatic and individual factors affect animal productivity.

Volumetric MicroCT Intensity Histograms of Fatty Infiltration Correlate with the Mechanical Strength of Rotator Cuff Repairs: An Ex Vivo Rabbit Model

BACKGROUND

Fatty infiltration of the rotator cuff occurs after injury to the tendon and results in a buildup of adipose in the muscle. Fatty infiltration may be a biomarker for predicting future injuries and mechanical properties after tendon repair. As such, quantifying fatty infiltration accurately could be a relevant metric for determining the success of tendon repairs. Currently, fatty infiltration is quantified by an experienced observer using the Goutallier or Fuchs staging system, but because such score-based quantification systems rely on subjective assessments, newer techniques using semiautomated analyses in CT and MRI were developed and have met with varying degrees of success. However, semiautomated analyses of CT and MRI results remain limited in cases where only a few two-dimensional slices of tissue are examined and applied to the three-dimensional (3-D) tissue structure. We propose that it is feasible to assess fatty infiltration within the 3-D volume of muscle and tendon in a semiautomated fashion by selecting anatomic features and examining descriptive metrics of intensity histograms collected from a cylinder placed within the central volume of the muscle and tendon of interest.

QUESTIONS/PURPOSES

(1) Do descriptive metrics (mean and SD) of intensity histograms from microCT images correlate with the percentage of fat present in muscle after rotator cuff repair? (2) Do descriptive metrics of intensity histograms correlate with the maximum load during mechanical testing of rotator cuff repairs?

METHODS

We developed a custom semiautomated program to generate intensity histograms based on user-selected anatomic features. MicroCT images were obtained from 12 adult female New Zealand White rabbits (age 8 to 12 months, weight 3.7 kg ± 5 kg) that were randomized to surgical repair or sham repair of an induced infraspinatus defect. Intensity histograms were generated from images of the operative and contralateral intact shoulder in these rabbits which were presented to the user in a random order without identifying information to minimize sources of bias. The mean and SD of the intensity histograms were calculated and compared with the total percentage of the volume threshold as fat. Patterns of fat identified were qualitatively compared with histologic samples to confirm that thresholding was detecting fat. We conducted monotonic tensile strength-to-failure tests of the humeral-infraspinatus bone-tendon-muscle complex, and evaluated associations between histogram mean and SDs and maximum load.

RESULTS

The total percentage of fat was negatively correlated with the intensity histogram mean (Pearson correlation coefficient -0.92; p < 0.001) and positively with intensity histogram SD (Pearson correlation coefficient 0.88; p < 0.001), suggesting that the increase in fat leads to a reduction and wider variability in volumetric tissue density. The percentage of fat content was also negatively correlated with the maximum load during mechanical testing (Pearson correlation coefficient -78; p = 0.001), indicating that as the percentage of fat in the volume increases, the mechanical strength of the repair decreases. Furthermore, the intensity histogram mean was positively correlated with maximum load (Pearson correlation coefficient 0.77; p = 0.001) and histogram SD was negatively correlated with maximum load (Pearson correlation coefficient -0.72; p = 0.004). These correlations were strengthened by normalizing maximum load to account for animal size (Pearson correlation coefficient 0.86 and -0.9, respectively), indicating that as histogram mean decreases, the maximum load of the repair decreases and as histogram spread increases, the maximum load decreases.

CONCLUSION

In this ex vivo rabbit model, a semiautomated approach to quantifying fat on microCT images was a noninvasive way of quantifying fatty infiltration associated with the strength of tendon healing.

CLINICAL RELEVANCE

Histogram-derived variables may be useful as surrogate measures of repair strength after rotator cuff repair. The preclinical results presented here provide a foundation for future studies to translate this technique to patient studies and additional imaging modalities. This semiautomated method provides an accessible approach to quantification of fatty infiltration by users of varying experience and can be easily adapted to any intensity-based imaging approach. To translate this approach to clinical practice, this technique should be calibrated for MRI or conventional CT imaging and applied to patient scans. Further investigations are needed to assess the correlation of volumetric intensity histogram descriptive metrics to clinical mechanical outcomes.

A Comparison of the Quality of Meat from Female and Male Californian and Flemish Giant Gray Rabbits

This study aimed to compare the quality of meat (Longissimus thoracis et lumborum-LTL, hind legs-HL) from female and male Californian (CAL) and Flemish Giant Gray (FG) rabbits. The animals were kept outdoor, in a roofed pavilion, in wire mesh cages with a slatted floor and were fed ad libitum a complete pelleted diet. All rabbits were slaughtered at 91 days of age. The meat of CAL rabbits had a higher content of dry matter (p < 0.001), protein (p < 0.001) and unsaturated fatty acids (p = 0.002), higher pH (p < 0.001), and higher taste desirability (p = 0.021) and tenderness (p = 0.046). CAL rabbit meat had also a lower (p < 0.001) water to protein (W/P) ratio, lower (p < 0.001) shear force values, and lower (p = 0.042) taste intensity. The meat of FG rabbits was characterized by lower (p < 0.001) water-holding capacity (WHC). The LTL muscle had a higher content of dry matter (p = 0.003) and protein (p < 0.001), higher L* (lightness) (p = 0.011), b* (yellowness) (p < 0.001), and C* (chroma) (p = 0.010) values, and lower (p = 0.015) WHC. Hind leg muscles had higher (p < 0.001) fat content, a higher (p < 0.001) W/P ratio, and pH (p < 0.001). Sex had no effect (p > 0.05) on the analyzed meat quality attributes, excluding vitamin A content which was higher (p = 0.041) in females. In conclusion, the meat of CAL rabbits slaughtered at 91 days of age can be more mature than the meat of FG rabbits slaughtered at the same age. Furthermore, quality of meat from rabbits of both breeds depends on the anatomical origin of muscles. Further research is needed to identify the possible reasons for the higher vitamin A content of meat from female rabbits which did not differ from the meat of males in terms of other characteristics.

Influence of multi-enzyme preparation supplemented with sodium butyrate on growth performance blood profiles and economic benefit of growing rabbits

The present study was carried out to explore the impacts of dietary supplementation of enzyme mixture with sodium butyrate on the growth performance, carcass traits, blood profile and economic benefit in two breeds of weanling rabbits adapted to survive in Egypt (New Zealand White and Rex). One-hundred and twenty weaned male rabbits (New Zealand White and Rex) of 6 weeks of age and 770.5 ± 20 g body weight were allotted randomly into four groups in a factorial arrangement. The obtained results indicated that there were non-significant differences in all growth performance traits, blood profile and economic parameters due to the breed effect. However, there were significant differences in most of carcass traits due to the breed effect except total giblets and New Zealand White breed showed the highest value of these parameters including dressing % (p < .01), forequarter and loin % (p < .001) and hindquarter % (p < .003) compared with Rex breed counterparts. The effect of the treatment and its interaction with the breed significantly (p < .05) improved body weight gain, feed consumption and carcass traits (percentage of dressing, forequarter, hind quarter and lion). However, final body weight and feed conversion ratio were not significantly influenced. Supplementing a diet with treatment significantly decreased blood triglycerides, cholesterol and the ratio between albumin and globulin (A/G ratio), while increased blood total protein and globulin. Although higher feed cost and total costs in treated groups than control ones in each breed, they showed higher total return and net return. Rex non-treated rabbit breed showed the lowest profitability measures compared with other groups. In conclusion, dietary supplementation of multi-enzyme with sodium butyrate is highly recommended in growing rabbits due to their beneficial effects on the growth performance and profitability.

Comparative evaluation of the quality and fatty acid profile of meat from brown hares and domestic rabbits offered the same diet

Since animal diets have a strong influence on meat quality, a comparative study on farmed brown hares and domestic rabbits offered the same diet was undertaken to assess the physical and chemical properties of their meat. Ten brown hares and ten domestic rabbits were used to characterize the traits of meat from the foreleg, hind leg, and Longissimus lumborum muscles. The study indicated higher protein content in hare meat than in rabbit meat. The meat of hares had a concentration of heme iron that was more than twice as high as that of rabbits. Lower SFA and MUFA content and higher PUFA content contributed to the superior PUFA/SFA ratio in hares. An unfavorable n-6/n-3 ratio but superior atherogenic and thrombogenic indices was observed for hare meat. The higher TBARS of hares indicated a higher susceptibility of hare meat to lipid oxidation. Hare meat was also characterized by a higher water holding capacity and higher color indices (redness and chroma).

Rabbit meat production and consumption: State of knowledge and future perspectives

Since the 1970s, in some European countries rabbit meat production has progressively become a highly specialized industry, which has made Europe the second (after China) largest rabbit meat producer in the world. However, the industry is currently facing a critical period due to structural weaknesses, progressive and constant reductions in consumption, and raising criticism related to welfare conditions and other ethical issues. This trend is questioning the future of the rabbit meat industry, which could lead to the loss of knowledge and technical expertise acquired over decades of major investments and research efforts (a valuable cultural and professional heritage for future generations). In the present review, we provide an overview of the rabbit meat industry, market and value chain, we depict consumer's attitude towards rabbit meat, highlighting strengths and weaknesses, and factors driving their current purchase behavior. Finally, we will attempt to outline possible strategies to ensure a sustainable future for the production of rabbits for commercial meat purposes.

Effect of age and gender on carcass traits and meat quality of farmed brown hares

A total of 48 sub-adult hares and adult reproducing farmed hares were used to characterize carcass and meat traits according to the age and gender of animals. With respect to carcass traits, when age increased, the carcass weight significantly increased (2022 to 3391 g; P<0.001), but dressing out percentages did not change. The dissectible fat (1.3% to 2.2%; P<0.05) and Longissimus lumborum (LL) proportions (13.5% to 14.5%; P<0.001) and muscle-to-bone ratio of hind legs (5.11 to 6.23; P<0.001) increased, whereas the hind leg proportions decreased (37.3% to 36.3%; P=0.01). As for the meat quality, the pH of hind leg (5.74 to 5.83; P<0.001) and LL (5.53 to 5.69; P<0.001) increased with age, while the L* index decreased in both cuts (42.9 to 34.4 in hind leg; 45.1 to 40.3 in LL; P<0.001). The redness index increased at the hind leg (4.07 to 5.76; P<0.001), while it decreased at LL (3.03 to 1.46; P<0.001). In the case of the hind leg, meat thawing losses decreased (1.58% to 1.02%), and shear force increased (2.97 to 4.02 kg/g). In the case of LL, thawing losses decreased (8.79% to 4.91%; P<0.001) in the adult hares compared with the sub-adult ones. Meat water and protein contents decreased in the hind leg and LL of the adult hares compared with the sub-adult ones, whereas ether extract increased in a restricted range in LL only (0.92% to 1.11%; P<0.001). In the case of the hind leg, the rate of the saturated fatty acids (SFA) decreased (41.0% to 26.7%), and the rate of the polyunsaturated fatty acids (PUFA) increased (34.0% to 45.3%) (P<0.001). In the case of LL, SFA (38.6% to 42.9%) and monounsaturated fatty acids (19.4% to 27.2%) increased, whereas PUFA decreased (42.0% to 30.1%) when the age increased (P<0.001). Gender affected only the slaughter results and carcass traits. In conclusion, farmed hares have favourable slaughter results (high dressing percentage), carcass traits (high hind legs and loins rates), and meat nutritional value (high-protein, low-fat meat). This fact would offer additional commercial opportunities, in addition to restocking, to hare farmers.

Performance and sustainability of two alternative rabbit breeding systems

<p>The aim of this study was to evaluate 2 alternative breeding systems that differ from the current system in terms of reproduction rhythm, age of females at first insemination and the age of kits at weaning and at slaughter. We measured the performance of 332 females and their offspring over 4 consecutive cycles, as well as the sustainability of the systems. We compared an intensive (group I: reproduction rhythm [RR]=35 d; first insemination [AI₁]=20.6 wk of age; weaning age [WA]=32 d; slaughter age [WS]=63 d) an extensive (group E: RR=49 d; AI₁=16.6 wk; WA=30 d; WS=70 d) and a semi-intensive system (group S: RR=42 d; AI₁=19.6 wk; WA=35 d; WS=70 d) considered as the control system. Sustainability was evaluated using a multicriteria assessment method that takes 14 economic, environmental and social criteria into account, for which 3 to 5 indicators were expressed as the relative score [–1; –0.5; 0; +0.5; +1] for alternative systems compared to the control system. The productivity measured at 28 d (3.5, 4.2 and 4.6 kg/AI, for groups I, S and E, respectively), at 63 d post-partum (30, 38 and 42 kg/female for 4 cycles, respectively), and the total body energy measured 3 d after the 1st and at the 4th insemination (45.4, 46.8 and 49.5 MJ, respectively), were significantly increased when the reproductive rhythm decreased (P&lt;0.001). Before and after weaning, kit mortality decreased when the reproduction rhythm decreased (11.4, 7.3, and 1.9% and 18.3, 15.3 and 10.6% for groups I, S and E, respectively, P&lt;0.05). Carcass quality (weight and dressing percentage) was lower in I than in the S and E groups (P&lt;0.001). On this basis, the yearly productivity per doe at weaning could be estimated at 79, 83, and 78 kg for groups I, S and E, respectively. Consequently, the productivity per reproductive cycle increases with the extensification of the breeding system. Nevertheless, compared with the current French system (S), simultaneous changes in several breeding practices could lead to new coherent and functional systems capable of improving various aspects of sustainability.</p>

Meat physical quality and muscle fibre properties of rabbit meat as affected by the sire breed, season, parity order and gender in an organic production system

<p>The aim of the study was to evaluate some meat physical quality and muscle fibre properties of rabbit meat when considering 2 sire breeds (SB: Vienna Blue [VB]; Burgundy Fawn [BF]; both coloured and slow-growing breeds), several parity orders (P: 1, 2, ≥3), gender (G), and 2 slaughter seasons (SS: spring, summer) in an organic production system. The effect of storage time (ST) at frozen state (2 mo at –20°C) of <em>Longissimus lumborum</em> (LL) meat was also evaluated. Animals were slaughtered when they reached 2.8 kg of live weight. Then, pH and L*a*b* colour values of <em>Biceps femoris</em> (BF) and LL muscles, water loss and Warner-Bratzler shear force of LL and hind leg (HL) meat, and the fibre typing and enzymatic activity of LL muscle were analysed. LL meat from females showed higher b* values than males (0.04 vs. –1.25; P&lt;0.05). Significant (P&lt;0.05) SB×P, SB×G and P×G interactions were observed for the b* value of LL: VB and BF crossbreds presented a higher b* value when born as P≥3 and P2 respectively, VB females showed higher b* value than VB males, and P2 and P≥3 produced males with a significantly lower b* value. HL thawing losses were significantly (P&lt;0.05) higher in rabbits slaughtered in summer than in those slaughtered in spring, whereas the opposite result was obtained for LL meat (P&lt;0.01). Cooking loss of LL meat was significantly lower in P2 group than P≥3 group (P&lt;0.05). The lactate dehydrogenase activity in LL muscle was higher in VB than in BF crossbreds (930 vs. 830 IU; P&lt;0.05), albeit not supported by differences in fibre type distribution. The ST significantly (P&lt;0.01) reduced pH, a* and b* colour values, and increased lightness of LL meat. It was concluded that the crossbreeds derived from VB and BF genotypes and farmed organically did not show remarkable sexual dimorphism, considering their elder slaughter age than rabbits reared under intensive conditions. Physical quality of meat was mainly affected by slaughter season, indicating that in the organic rearing system, specific attention needs to be paid to the farming environmental conditions.</p>