Rabbits Divergently Selected for Total Body Fat Content: Changes in Proximate Composition and Fatty Acids of Different Meat Portions.

The present research studied the potential of a four-generation divergent selection (Pannon maternal rabbit lines) based on the total body fat content to create two rabbit lines with different meat attributes: a Fat line to deliver greater amounts of healthy fatty acids for newborns and infants, and a Lean line intended to provide lean meat for everyday consumption. Selection was based on the fat index calculated in 10-week-old live rabbits by means of computed tomography (CT). For each generation, 60 rabbits/line were fed ad libitum with commercial pellet from weaning (5 weeks) to slaughter (11 weeks). A total of 15 rabbits/line were randomly selected for meat quality evaluations: the longissimus thoracis et lumborum muscles (LTLs), hind legs (HLs), forelegs (FLs) and abdominal wall (AW) were analyzed for their proximate composition and fatty acid (FA) profile. FA contents were also calculated. Results highlighted that it was possible to obtain leaner meat for everyday consumption in most meat portions starting from generation 4 (7.93 vs. 11.9, 5.10 vs. 5.98 and 7.26 vs. 10.9 g of lipids/100 g of meat in Lean and Fat groups for the FLs, HLs and AW, respectively). The sole exception was the LTLs, which were not affected by the divergent selection. The total PUFA amount increased in FL and AW (p < 0.05) portions of the Fat line only, attributable to a greater n-3 amount (151 vs. 216 and 73 vs. 143 mg/100 g of meat in Lean and Fat groups for the FLs and AW, respectively).

Rabbit Lines Divergently Selected for Total Body Fat Content: Correlated Responses on Growth Performance and Carcass Traits.

The aim of this experiment was to study the effect of divergently selected rabbits for total body fat content (fat index) on growth performance and carcass traits. The fat index was determined at 10 weeks of age by computed tomography and lasted for four consecutive generations. The rabbits with the lowest fat index belonged to the lean line and those of the highest values belonged to the fat line. At generation four, 60 rabbits/line were housed in wire-mesh cages and fed with commercial pellet ad libitum from weaning (5 w of age) to slaughtering (11 w of age). Growth performance, dressing out percentage and carcass adiposity were measured. The lean line showed a better feed conversion ratio (p < 0.001) than the fat line. Furthermore, the carcass of the lean rabbits had the highest proportion of fore (p < 0.020) and hind (p < 0.006) parts. On the contrary, rabbits of the fat line had the highest carcass adiposity (p < 0.001). The divergent selection for total body fat content showed to be effective for both lean and fat lines. Selection for lower total body fat content could be useful for terminal male lines, while the selection for higher total body fat content could be an advantage for rabbit does in providing fat (energy) reserves.

Inbreeding depression for kit survival at birth in a rabbit population under long-term selection.

BACKGROUND: Accumulation of detrimental mutations in small populations leads to inbreeding depression of fitness traits and a higher frequency of genetic defects, thus increasing risk of extinction. Our objective was to quantify the magnitude of inbreeding depression for survival at birth, in a closed rabbit population under long-term selection. METHODS: We used an information theory-based approach and multi-model inference to estimate inbreeding depression and its purging with respect to the trait 'kit survival at birth' over a 25-year period in a closed population of Pannon White rabbits, by analysing 22,718 kindling records. Generalised linear mixed models based on the logit link function were applied, which take polygenic random effects into account. RESULTS: Our results indicated that inbreeding depression occurred during the period 1992-1997, based on significant estimates of the z-standardised classical inbreeding coefficient z.FL (CI95% - 0.12 to - 0.03) and of the new inbreeding coefficient of the litter z.FNEWL (CI95% - 0.13 to - 0.04) as well as a 59.2% reduction in contributing founders. Inbreeding depression disappeared during the periods 1997-2007 and 2007-2017. For the period 1992-1997, the best model resulted in a significantly negative standardised estimate of the new inbreeding coefficient of the litter and a significantly positive standardised estimate of Kalinowski's ancestral inbreeding coefficient of the litter (CI95% 0.01 to 0.17), which indicated purging of detrimental load. Kindling season and parity had effects on survival at birth that differed across the three periods of 1992-1997, 1997-2007 and 2007-2017. CONCLUSIONS: Our results support the existence of inbreeding depression and its purging with respect to kit survival at birth in this Pannon White rabbit population. However, we were unable to exclude possible confounding from the effects of parity and potentially other environmental factors during the study period, thus our results need to be extended and confirmed in other populations.

Aggressiveness, Mating Behaviour and Lifespan of Group Housed Rabbit Does.

Aggressiveness is one of the main problems in group housing of rabbit does. The aim of the experiment was to investigate the frequency of aggressiveness and mating behaviour as well as the lifespan of does depending on group composition. The female and male rabbits were housed in one of the 7.7 m2 pens (four females and one male per pen). Based on the ages of female rabbits two homogenous groups (HOM) were formed containing four 17-week-old females and two heterogeneous groups (HET) containing three 17-week-old and one 1-year-old female. Twenty-four-hour video recordings were taken during the first month after assembling the groups, and the aggressive actions (fights) and matings were counted. The lifespan was examined over a 200-day experimental period. On the day after assembling the groups the number of fights among does was high in HET group. The same aggressive behaviour only started a week later in HOM group, and some fights between females and the male were also observed. The daily peaks of aggressiveness were in the morning (after the light on) and in the evening (before and after the lights off). The primary position of females in the hierarchy was clear but sometimes no differences were detected among the subordinate females. The mortality of does was connected with their rank order. The number of matings was very high on the day of assembling the groups and a second small peak was observed at the end of the hypothetical pseudo-pregnancy. In addition to mating between male and females, female-female and female-male mounting was also observed. Despite of the small sample size it seems that aggressive behaviour is frequent in group housing systems, which is contrary to animal welfare. Natural mating is not effective in group-housing system.

Housing Rabbit Does in a Combi System with Removable Walls: Effect on Behaviour and Reproductive Performance.

We evaluated the effects of two types of colony cages, in which rabbit does were always in a group (C1), and where they were in combi cages furnished with removable internal walls to allow both individual and grouphousing (C2), in addition to the control group (C: conventional individual cage), on welfare, reproductive performance, and global efficiency. Forty-eight New Zealand White nulliparous rabbit does underwent artificially insemination (AI) and were divided into three groups, and reared in the different systems for about 1 year. The reproductive rhythm provides AIs at weaning (30d). In the C1 system, does were continuously grouped, while in C2, walls were inserted four days before kindling and removed 1week after it (60% of the timesheet in group). Reproductive traits and behaviour were evaluated during the entire year. The behavioural observations were performed around days 7, 36, and 44, corresponding to the inclusion of the does in the maternal cages, the insertion of walls four days before kindling, and the removal of the walls 1week after parturition in the C2 group, respectively. The percentages of does with severe skin injuries and the distribution of the injuries on different parts of body were also registered. Does reared in conventional cages showed the greatest presence of stereotype behaviours, while the C1 group showed the highest (p < 0.05) incidence of aggressiveness after regrouping (attack, dominance features, and lower allo-grooming) in comparison to the C2 group (17% and 22%, in C2 and C1 does, respectively).Individually caged does achieved the best productive performance (sexual receptivity, fertility, kindling rate, and number of kits born alive and at weaning). The C1 group showed the lowest performance (p < 0.05), whereas C2 showed an intermediate one. Does housed in the combi cage (C2) had higher (p < 0.05) receptivity and fertility rates and higher numbers of kits born alive and at weaning (79.2% and 76.2%; 7.95 and 7.20, respectively) than the C1 group, but lower values (p < 0.05) than does that were individually housed.

The antioxidant effectiveness of liquorice (Glycyrrhiza glabra L.) extract administered as dietary supplementation and/or as a burger additive in rabbit meat.

The present research studied the effect of liquorice extract (in feed and/or directly in burgers) on the shelf-life of rabbit meat. Before weaning, 28 individually caged rabbit does with their litters were divided in two dietary groups: Control, receiving a commercial diet, and Liquorice, receiving the Control diet supplemented with 6 g liquorice extract/kg (L). At 12 weeks of age, 15 fattened rabbits/treatment (one rabbit/cage) were slaughtered and their hindlegs dissected. Hindleg meat was trimmed, individually minced and divided into two parts: one of them was mixed with 0.25% (w/w) L. Storage time significantly reduced the amount of polyunsaturated fatty acids in the burger, to a different magnitude depending on the unsaturation level, experimental group and storage time. The α-tocopherol content showed higher levels during storage in the burgers from the Liquorice group. Also TBARs values showed a significant positive effect of dietary liquorice and a progressive increase at days 3 and 6 of storage.

Supplementing growing rabbit diets with chestnut hydrolyzable tannins: Effect on meat quality and oxidative status, nutrient digestibilities, and content of tannin metabolites.

The study investigated the effect of dietary inclusion of chestnut hydrolyzable tannin (CHT) in growing rabbit diets on nutrients digestibility, quality and oxidative status of meat, and content of tannin metabolites. At weaning, rabbits were assigned to 5 dietary groups (n = 72 rabbits/diet): control medication-free (Co), control with coccidiostat (Cc), and T200, T400 and T600 (diets supplemented with 200, 400 and 600 g/100 kg CHT extract). Sixteen carcasses/treatment were considered and hindleg meat and Longissimus thoracis et lumborum (LTL) muscle were used for analyses. L*a*b* color values, water holding capacity, Warner Bratzler shear force, haem iron content, oxidative status and nutritional quality were unaffected by dietary treatments. Saturated fatty acids (SFA) and monounsaturated FA (MUFA) in LTL meat were higher in T600 than Cc rabbits (P < .05), even though no differences were found for SFA and MUFA digestibility. Contrarily, polyunsaturated FA digestibility was lower in T400 and T600 than Co rabbits. No tannin metabolites traces were found in rabbit meat. Results of the present study showed that feeding CHT did not improve rabbit meat quality.

Effect of diet and packaging system on the oxidative status and polyunsaturated fatty acid content of rabbit meat during retail display.

The aim of this study was to evaluate the combined effect of two dietary lipid sources (sunflower vs. linseed oil) and three packaging methods (PVC film - BAG vs. modified atmosphere CO2 20% + 80% O2 - MAP vs. and vacuum - VAC) on the oxidative status and polyunsaturated fatty acid content of rabbit loins (Longissimus thoracis et lumborum muscle), at days 1, 4 and 10 of simulated retail display. The diet, storage time and packaging method affected the oxidative status of rabbit meat under retail display. As expected, storage time, independently on the other factors, significantly reduced the antioxidant content of loin meat. Accordingly, TBARs values significantly increased during storage, as well as the dietary supplementation of linseed. The fatty acid profile of the fresh loin closely respected that of the diets. At day 10, oxidative status and fatty acid profile of MAP samples could be yet considered optimal.

Effect of diet and packaging system on the microbial status, pH, color and sensory traits of rabbit meat evaluated during chilled storage.

The combined effect of two dietary lipid sources (sunflower vs linseed oil) and three packaging methods (PVC film - BAG, modified atmosphere CO2 20% + 80% O2 - MAP, and vacuum - VAC) on the shelf-life (pH, color, microbial count, sensory traits) of rabbit loins was tested at days 1, 4 and 10 of refrigerated storage. Linseed oil did not adversely affect neither the physical or sensory traits, nor the microbiological quality of rabbit meat throughout the shelf-life trial. The three packaging methods were all similarly effective in maintaining the physical and sensory quality of the meat, irrespective of the different dietary lipid sources and thus different susceptibility to oxidation. MAP and VAC were more effective than BAG in preserving rabbit meat hygienic quality, as highlighted by the microbial count analyzed at day 4 of shelf-life (P < 0.001). At day 10, the microbiological quality didn't differ between MAP and VAC rabbit meat samples.

Effect of turmeric powder (Curcuma longa L.) and ascorbic acid on physical characteristics and oxidative status of fresh and stored rabbit burgers.

The objective of this study was to evaluate the effect of Curcuma longa powder and ascorbic acid on some quality traits of rabbit burgers. The burgers (burgers control with no additives; burgers with 3.5 g of turmeric powder/100g meat; burgers with 0.1g of ascorbic acid/100g meat) were analyzed at Days 0 and 7 for pH, color, drip loss, cooking loss, fatty acid profile, TBARS, antioxidant capacity (ABTS, DPPH and FRAP) and microbial growth. The addition of turmeric powder modified the meat color, produced an antioxidant capacity similar to ascorbic acid and determined a lower cooking loss than other formulations. Turmeric powder might be considered as a useful natural antioxidant, increasing the quality and extending the shelf life of rabbit burgers.

Dietary Spirulina (Arthrospira platensis) and Thyme (Thymus vulgaris) supplementation to growing rabbits: effects on raw and cooked meat quality, nutrient true retention and oxidative stability.

The study evaluated the effect of Spirulina and Thyme dietary supplementation on rabbit meat quality, nutrient true retention and protection against oxidative stress. Rabbits in the control group (C-C) received a non-supplemented pellet throughout the experiment (5-11weeks of age). In the other groups, the pellet contained 5% Spirulina (S), 3% Thyme (T), or both (ST) for either the entire (groups S-S, T-T, ST-ST) or only the final part of the growing period (8-11weeks: groups C-S, C-T, C-ST). Spirulina supplementation increased the γ-linolenic acid content of rabbit meat, whereas Thyme improved the oxidative stability of raw and freeze-dried meat.

The role of rabbit meat as functional food.

Increasing consumer knowledge of the link between diet and health has raised the awareness and demand for functional food ingredients. Meat and its derivatives may be considered functional foods to the extent that they contain numerous compounds thought to be functional. This review will attempt to outline the excellent nutritional and dietetic properties of rabbit meat and offer an overview of the studies performed on the strategies adopted to improve the functional value of rabbit meat. Dietary manipulation has been seen to be very effective in increasing the levels of essential FA, EPA, DHA, CLA, branched chain FA, vitamin E, and selenium in rabbit meat. Dietary fortification with vitamin E or natural products such as oregano essential oil, chia seed oil, and Spirulina platensis microalga seem promising in improving the oxidative stability of rabbit meat while also adding functional ingredients.

Effect of nursing methods and faeces consumption on the development of the bacteroides, lactobacillus and coliform flora in the caecum of the newborn rabbits.

The effect of nursing method and ingestion of maternal faeces on the development of the bacteroides, lactobacillus and coliform flora of the caecum in the first 10 days of life were examined in freely nursed pups having access to maternal faeces (Group FF), pups nursed once a day and having access (Group CF), or having no access (Group CN) to maternal faeces. Colonisation of the caecum by Bacteroides commenced already on day 3 after birth. On day 2 the bacteroides counts were below 100, while on day 4 they were already between 100 and 10,000. In Group CN, the Bacteroides counts were lower (by 14 to 40%) throughout the 10-day period studied than in the groups having access to maternal faeces. Differences between groups were significant only on days 4 and 6. The average number of maternal faecal pellets left behind the doe in Group CN was 3-4 (between 0.5 and 6.4 per doe). In Groups FF and CF the pellets became smaller, crumbled and finally disappeared from the nest box, they were consumed by the pups and could be found in their gastric content. The lactobacillus counts decreased in all three groups with age, from 6.0 to 3.5 log10 CFU.g-1 (FF), 4.6 to 2.8 log10 CFU.g-1 (CF) and 5.1 to 3.1 log10 CFU.g-1 (CN), respectively. The coliform counts were higher in the first 4 days in FF (5.6 log10 CFU.g-1) than in CF (< 2 log10 CFU.g-1) and CN (2-3.6 log10 CFU.g-1) animals. Bacteroides could be cultured from the surface of the vulvar labia (max. 1000 colony count) and the vagina (max. 190 colony count), so young rabbits could become "infected" by them already in the doe's vagina. Thus prevention of ingestion of maternal faeces only slightly influenced the development of the bacteroides flora, the faeces left behind by the doe did not play an exclusive role in their colonisation.