Carcass composition, bone mechanical properties, and meat quality traits in relation to growth rate in rabbits1

Abstract

The objective of this study was to characterize correlated responses in carcass composition, bone mechanical properties, and meat quality indicators to divergent selection for growth rate. Rabbits from low (LOW) or high (HIGH) lines divergently selected over five generations on 63-d BW and a control group (CONT) were used. Rabbits were slaughtered at an average BW of 2,306 +/- 65 g, corresponding to 63, 58, or 52 d of age in LOW (n = 41), CONT (n = 43), and HIGH (n = 44) groups, respectively. Postweaning ADG and G:F increased (P < 0.001) in the order LOW < CONT < HIGH groups. The lengths of the tibia and femur in rabbit legs decreased (P < 0.001) with increasing growth rate. Tibia and femur bone intrinsic stiffness, as assessed by a three-point flexure test, followed the order (P < 0.001) of HIGH < CONT < LOW groups. At the same BW, HIGH rabbits and CONT rabbits showed many similarities for dressing percent, carcass composition, and color and chemical composition of muscles or meat parts. In contrast, carcass yield and the relative proportion of hind part were 3% greater (P < 0.01) in LOW rabbits than in CONT and HIGH rabbits. The meat-to-bone ratio in the hind leg was 11% greater (P < 0.001) in the LOW group compared with the CONT and HIGH groups. Yellow color index and moisture content in LM, a fast-twitch glycolytic muscle, were lower (P < 0.05) in LOW rabbits than in HIGH rabbits, but ultimate pH, WHC, and cooking loss did not differ between the two growth-selected lines. Ultimate pH in semitendinosus, a mixed slow- and fast-twitch oxidoglycolytic muscle, was less (P < 0.001) in HIGH rabbits than in CONT and LOW rabbits. However, lactate dehydrogenase and isocitrate dehydrogenase activities in this muscle (n = 21 per group), assessed at the time of slaughter as markers of glycolytic and oxidative capacities, respectively, did not differ among groups. Growth rate did not modify mean cross-sectional area and type frequency of myofibers in semitendinosus muscle. Finally, Warner-Bratzler shear force and total energy needed to achieve rupture did not differ among groups in semitendinosus muscle (n = 21 per group), whereas they were the least (P < 0.001) in LM (n = 128) from HIGH rabbits. Results from this study indicate that improvement of growth rate by selection has little effect in rabbit carcass and meat quality traits.

Embryo vitrification in rabbits: Consequences for progeny growth

“…Cryopreservation of mammalian embryos has benefitted both breeding and biomedical research in recent decades, due in part to the improvement of techniques related to vitrification, freezing-thawing processes, and transfer procedures. To this end, rabbit embryo banking has allowed the preservation and spread of genetically superior animals over different countries [34] and the possibility of evaluating the genetic gain in maternal lines [4][5][6][7] without cumulative genetic drift variance [35]. Nevertheless, it is known that these techniques induce changes in environ-mental and maternal side effects modifying the embryo gene expression and methylation pattern [19,20,36], the transcriptomic and proteomic placental profile [21], and their viability [29,37], but little is known regarding the long-term effects on the derived progeny.…”

“…Strain rederivation from cryopreserved embryos has been used to assess the genetic improvement of quantitative traits such as prenatal survival, litter size, and growth characteristics in polytocous species such as mice, rats, and rabbits [4][5][6][7].…”

Genotype and gender effects on sheep limb bone growth and maturation: selection for loin depth causes bone hypotrophy

“…Third, selection for loin depth may be acting through hormonal drivers of bone growth such as growth hormone (GH), since sheep expressing excess GH show increased bone growth yet relative under-muscling (Adams et al 2006), the opposite to that observed in the PD m × M genotype in the present study. Alternatively, a more prosaic explanation is that selection for PEMD EBV, which is referenced to bodyweight (Hall et al 2002) may inadvertently produce selection pressure for lighter appendages thus shorter limbs, as has been shown in other production animals such as rabbits (Gondret et al 2005) and broiler chickens (Reddish and Lilburn 2004). However, other data from this study demonstrating shorter carcass length in PD m × M compared with PD g × M animals (Ponnampalam et al 2007a), suggest that limb shortness is indicative of more generalised skeletal hypotrophy in this genotype.…”

Age-related changes in muscle fiber type frequencies and cross-sectional areas in straightbred and crossbred rabbits

“…Selection for growth rate in rabbits has resulted in myofiber hypertrophy (Gondret et al, 2002), together with increased (Pascual and Pla, 2007) or unchanged (Hernandez et al, 2004) oxidative traits evaluated through enzymatic activity. Although a lower proportion of slow-type myosin heavy chain has been demonstrated in rabbits selected for a rapid growth rate (Ramírez et al, 2004), no changes in the relative proportion of fiber types as evaluated by m-ATPase histochemistry have been elicited (Gondret et al, 2005).…”