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).

A 65-Day Fumonisin B Exposure at High Dietary Levels Has Negligible Effects on the Testicular and Spermatological Parameters of Adult Rabbit Bucks.

A 65-day study was undertaken to test the effects of two doses (10 and 20 mg/kg) of dietary fumonisin Bs (FB) on the rabbit male reproduction system. Body and testicular weight was not affected by the intoxication, neither the fatty acid composition of the testicular total phospholipids; the testis histological analysis failed to reveal any toxic effect. The FBs increased the testicular concentration and activity of reduced glutathione and glutathione peroxidase and decreased initial phase lipid peroxidation (conjugated dienes and trienes) in a dose dependent manner. Sperm morphology and chromatin condensation were monitored on Feulgen-stained smears. No significant differences were observed between the treatment groups and between sampling time points. The live cell ratio in the sperm (as assessed with flow cytometry) was not different among groups at any of the five sampling timepoints and was also identical within groups. Similarly, the spermatozoa membrane lipid profile was also identical in all three groups after the total intoxication period. In summary, it was demonstrated that FBs in an unrealistic and unjustified high dose still do not exert any drastic harmful effect on the leporine, male reproduction system, meanwhile slightly augmenting testicular antioxidant response.

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.

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.

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.