Effect of energy restriction in interaction with genotype on the performance of growing rabbits: II. Carcass traits and meat quality

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.