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Abstract: The objective of the study was to analyze the effects of divergent selection for computer tomography (CT) measured thigh muscle volume (VTM) on the production and slaughter performance of growing rabbits. Pannon White rabbits were selected to increase (PP) or decrease (MM) their VTM during two generations. Production and slaughter traits of their offspring (the third generation) were measured for 25 MM and 57 PP and for 24 MM and 24 PP rabbits, respectively. Selection had no effect on daily weight gain and body weight at 10 week. PP rabbits had lower feed consumption (128 vs. 138g/d, P<0.05) and better feed conversion ratio (FCR) (2.81 vs. 3.01, P<0.001) compared to the MM group. CT measured VTM (309 vs. 336cm3, P<0.05), hind part weight (439 vs. 473g, P<0.001) and meat weight of the hind legs (HLMW) (326 vs. 355g, P<0.001) were higher in the PP group, while the perirenal fat weight (PFaW) (29.4 vs. 23.8g, P<0.05) and the periscapular fat weight (SFaW) (13.0 vs. 6.05g, P<0.001) were lower than that of the MM rabbits. The ratio of the full gastrointestinal tract compared to body weight (GIP) was not higher for the MM rabbits (18.1% vs. 16.7%). Compared to the reference carcass, ratios of the perirenal fat (PFaP) (2.40% vs. 1.90%, P<0.05) and periscapular fat (SFaP) (1.07% vs. 0.49%, P<0.001) were higher in the MM group while ratios of the hind part (HPP) (36.3% vs. 38.2%, P<0.001) and hind leg meat were higher (HLMP) in the PP group (26.9% vs. 28.7%, P<0.001). It was thus shown that CT aided selection can efficiently increase the thigh muscle volume. At the same time the volume of fat depots decreased while FCR also improved. [Copyright &y& Elsevier]

Abstract: In this experiment the effect of digestible energy (DE) restriction on carcass traits and meat quality of rabbits selected divergently for body fat content was studied. Using a 2×3 factorial arrangement, Pannon White rabbits selected for high (HFAT) or low (LFAT) total body fat content were fed isocaloric diets between 4 and 12 weeks of age. Energy restriction was achieved by reducing the daily feed intake by 10% (M) and 20% (L) compared to the ad libitum fed group (H). Proportional to the reduction of feed intake the nutrient density of diets M and L was increased. Thus, the DE intake was reduced while the nutrient intake remained stable among the 3 dietary groups. Effect of genetic group on carcass traits and on meat quality parameters was less marked than DE restriction. Selection for high body fat content improved the dressing out percentage (58.3 and 57.3% in HFAT and LFAT respectively; P <0.01), and reduced the percentage of the full gastrointestinal tract to slaughter weight (13.7 and 14.3% in HFAT and LFAT respectively; P <0.05). Reduction of DE intake decreased the body weight and the weight of the chilled and reference carcass (P <0.001), while it had no effect on dressing out percentage. In group H the percentage of fore part to reference carcass was higher (29.7 vs 29.0%; P <0.01) while that of the hind part was lower than in group L (37.0 vs 38.2%; P <0.001). The Longissimus lumborum meat from HFAT rabbits exhibited a lower content of moisture (76.1 and 76.5% in HFAT and LFAT respectively; P <0.01) as well as lower L⁎ (53.5 and 54.4 in HFAT and LFAT respectively; P <0.05) and b⁎ (0.42 and 0.81 in HFAT and LFAT respectively; P <0.05) colour values. When compared with ad libitum fed rabbits, those restricted at 20% (L) exhibited a higher content of moisture (76.9 vs 75.8%; P <0.01), as well as higher pHu (5.87 vs 5.73; P <0.01) associated with lower cooking loss (17.8 vs 19.1%; P <0.05). L rabbits also produced lower values of redness (a⁎, 2.21 vs 3.35; P <0.01) and yellowness (b⁎, 0.23 vs 0.91; P <0.01). No effect of the divergent selection for body fat content on the total lipid percentage and on most of the fatty acids in the meat of the hind leg was found. DE restriction resulted in lower SFA (L: 32.1 vs H: 35.8%; P <0.01) and MUFA (L: 21.0 vs H: 28.6; P <0.01) but higher PUFA contents (L: 45.5 vs H: 34.9%; P <0.01) in the hind leg meat. [Copyright &y& Elsevier]

Abstract: This 2×2×2 factorial experiment was conducted to study the effects of housing system (pair caged – cage – : 2 rabbits/0.122 m2 vs open top pen housed – pen – : 13 rabbits/0.86 m2; same stocking density), floor type (wire mesh vs plastic net), and environmental enrichment (with vs without gnawing stick) on the meat quality of Pannon White growing rabbits (n =64). The housing system significantly influenced slaughter weight (2590 vs 2531 g in cage or pen, respectively; P <0.01), reference carcass (RC) weight (1266 vs 1234 g; in cage or pen, respectively; P <0.05), and the hind leg meat to bone ratio (6.11 vs 5.62 in cage or pen, respectively, P <0.001). The animals reared in pens showed paler meat with lower pHu than that of those reared paired in cages. Hind leg meat dry matter and protein content were also influenced by the housing system (26.3 vs 25.9%, 21.9 vs 21.6%; in cage or pen, respectively; P <0.05). Pen housed rabbits had significantly heavier femur and tibia bone weight and higher fracture toughness than pair caged rabbits. Floor type affected the fore part/RC weight ratio (29.2 vs 29.6% of the RC on plastic net or wire mesh, respectively). Gnawing stick presence increased slaughter yield (59.0 vs 58.3%; P <0.05), RC weight (1266 vs 1236 g; P <0.05) and the forepart/RC ratio (29.6 vs 29.2% RC; P <0.05) while significantly reducing the meat colour b⁎ value and increasing m. Longissimus dorsi shear force (0.60 vs 0.50 kg/cm2; P <0.01). The hind leg meat fatty acid profile was only slightly influenced by experimental factors. Although this study showed pair caged rabbits to have increased carcass weight with better meatiness and other meat quality traits, hind leg bone strength was shown to be higher in pen housed rabbits. [Copyright &y& Elsevier]

Abstract: In a 2×2×2 factorial experiment the effects of housing system (pair caged (cage): 2 rabbits/0.122 m2 vs open top pen housed (pen): 13 rabbits/0.86 m2; same stocking density), floor type (wire mesh vs plastic net) and environmental enrichment (with vs without gnawing stick) were studied on live performance, health status and welfare (ear lesions) of growing rabbits (n =176). The housing system significantly influenced the body weight at 11 weeks of age (2630 vs 2557 g; in cage or pen, respectively) and the feed conversion (3.12 vs 3.38 g/g; in cage or pen, respectively). Floor type did not affect the traits tested. Gnawing stick consumption affected the body weight at 11 weeks of age (2553 vs 2622 g; without or with gnawing stick, respectively), the percentage of ear lesions (18.5 vs 1.20%; without or with gnawing stick, respectively). Some of the live performance traits of rabbits reared in pens was slightly lower. The presence of gnawing stick, especially in pens, reduced the aggressive behaviour and improved the welfare. [Copyright &y& Elsevier]

Abstract: Genetic parameters for average daily gain between the age of 5 and 10 weeks (ADG), the average cross-sectional area of the m. Longissimus dorsi (L) (between the 2nd–3rd and 4th–5th lumbar vertebrae-based on in vivo computerized tomography (CT)) and dressing out percentage (DoP) were estimated in a group of 28,686 Pannon White rabbits reared in 5044 litters and born between 2000 and 2003. Using multivariate animal models with Bayesian procedures, estimated heritabilities were moderate and moderately high for ADG, L and DoP (0.21 to 0.29, 0.25 to 0.42 and 0.19 to 0.71, respectively). Litter effects were moderate for ADG, L and DoP estimates (0.20 to 0.22, 0.10 to 0.18 and 0.09 to 0.30, respectively). Genetic correlation coefficient estimates between ADG and L and ADG and DoP were moderate and negative (−0.41 to −0.01, −0.70 to +0.10). A moderately high positive genetic correlation was found between L and DoP (0.13 to 0.83). [Copyright &y& Elsevier]