M. Pla

CARCASS CHARACTERISTICS AND MEAT QUALITY OF RABBIT LINES SELECTED FOR DIFFERENT OBJECTIVES : I. BETWEEN LINES COMPARISON

Abstract Rabbits from three lines (A, V, R), selected for different objectives, were slaughtered at three different liveweights (1800, 2050 and 2300 g). Lines A and V were selected for litter size at weaning, whereas line R was selected for growth rate between the 4th and 9th week of life. Fifteen animals of each of the nine combinations body weight group×line were used in the experiment. The composition of their carcasses as well as some of the characteristics of their meat were then compared. Dressing out percentage was between 51.48 of line R and 55.67 of line V. The thoracic cage was relatively more developed in lighter animals, they had less fat (0.8%) and had a smaller meat-to-bone ratio (4.16 v 4.87). The meat of the R line animals presented a higher pH, had less fat and loosed more water (40%) when cooked than the meat of line V (37.7%). We found significantly lower initial yield force (4.71) and maximum shear force (4.75) in line A in relation to the other two lines, being the line V (initial yield force=5.10 and maximum shear force=5.11) more close to line R (5.20 and 5.25, respectively). These results indicate a more tender meat in line A than in the other two lines. We can conclude that differences in tenderness in loin meat rabbit are more affected by genetic origin than by body weight. Females had more adipose tissue (4.07%) than males (3.65%). Female meat had a slightly more acid pH and retained more water.

Carcass characteristics and meat quality of rabbit lines selected for different objectives

Abstract Rabbits from three lines (A, V and R) and three different weights (1800, 2050, 2300 g) were used in the experiment. Nine animals of each line and weight were used. Lines A and V were selected for litter size at weaning, whereas line R was selected for growth rate between the 4th and 9th week of life. Muscular pH of Longissimus (pHLD) at the level of the 5th lumbar vertebra and pH of Biceps femoris (pHBF) were taken 24 h post-mortem. Colour (L* lightness, C* chroma, H* hue) was measured on the carcass surface of the Longissimus muscle at the level of the 4th lumbar vertebra and at the 7th lumbar vertebra cut. Fat and moisture were estimated on fore leg muscles (including insertion and thoracic muscles), hind leg, abdominal wall and Longissimus muscle. Water holding capacity, cooking loss (CL) and texture (shear force) were estimated on Longissimus muscle. A principal component analysis was performed in order to examine the relationships between the traits measured. The four 1st PC explained a 63% of the total variation (29%, 16%, 10% and 8%, respectively). The principal component analysis showed that meat quality traits were grouped in independent sets. Fat-moisture, texture, pH and luminosity of Longissimus explained a large part of the observed variation. The differences between lines or liveweight groups in meat quality tend to be small, which implies a certain constancy in rabbit meat quality.

Carcass Composition and Meat Characteristics of Two Rabbit Breeds of Different Degrees of Maturity

Carcass and meat characteristics of rabbits from two synthetic breeds of different size were compared. Breed R had a higher adult weight and reached slaughter weight 1 week before breed V. Sixty rabbits of each breed were slaughtered when they (approximately) reached the Spanish commercial liveweight of 2 kg in order to compare their carcasses and meat quality. The carcasses were measured and retailed according to the norms of the World Rabbit Scientific Association. Breed R had a considerably more developed liver, a less developed hind part, and a more developed thoracic cage. Dissectible fat content was 3.1% and 2.5% of the carcass weight for the breeds V and R, respectively. Meat content was higher in the V breed than in the R breed (53 and 51% with respect to the chilled carcases). The ratio meat bone was better for breed V (2.18 and 2.05, respectively). Muscular fat content, estimated in the meat of one side of the carcass, was higher for breed V. All these differences are related to the lower degree of maturity of breed R at equal weights. Muscular pH, measured on the B. femoris and on the M. Longissimus lumborum at the level of the 5th lumbar vertebra, was the same for both breeds. Colour was measured on the carcass surface and in cuts of the M. Longissimus lumborum. Some colour differences were found for the carcass surface, but not for the meat.

Effects of pig sire type and sex on carcass traits, meat quality and sensory quality of dry-cured ham

Five different sire types, Danish Duroc (DU), Dutch Large White (LWD), English Large White (LWE), Belgian Landrace × Landrace (BL × LR) and Belgian Landrace (BL), were mated with LR × LW crossbred sows. Their offspring were compared on carcass traits, meat quality measurements and sensory characteristics of dry-cured ham. An animal mixed model was used to analyse these traits. BL-sired pigs had the worst score for meat quality but the highest killing out proportion and the best carcass conformation, with a higher percentage of ham and shoulder. On the other hand, DU-sired pigs had a good score on meat quality measurements as well as low subcutaneous fat and a good carcass conformation. Sensory analysis of dry-cured ham revealed that the BL-sired pigs showed a high ‘rancid’ aroma, although this sire type presented a low ‘marbling’ appearance. Dry-cured ham from BL × LR-sired pigs was characterised by a high ‘fat complex’ aroma and a low level of ‘tyrosine crystals’, and from DU-sired pigs by high ‘marbling’ and ‘tyrosine crystals’ and a low aroma content. The females produced a higher percentage of ham and dry-cured ham with a higher ‘overall quality’ than the males. It can be concluded that the appropriate genetic type for dry-cured ham processing is the DU sire because of its high desirable ‘marbling’ descriptor. © 1999 Society of Chemical Industry

Effects of the terminal sire type and sex on pork muscle cathepsins (B, B+L and H), cysteine proteinase inhibitors and lipolytic enzyme activities

Pork muscle cathepsins (B, B+L, and H), cysteine proteinase inhibitors and lipolytic enzyme activities were measured in the offspring of five different genetic sire types: Danish Duroc (DU), Dutch Large White (LW(D)), English Large White (LW(E)), Belgian Landrace × Landrace (BL×LR) and Belgian Landrace (BL). Cathepsin B and B+L activities were higher for LW(E) and LW(D) sires than for BL×LR and BL. Cathepsin H activity showed an opposite evolution, being higher for BL and BL×LR sires than for DU, LW(D) and LW(E). Cysteine proteinase inhibitor activity was higher for LW(E) sires than for DU and BL. In lipolytic enzymes, BL sires had a lower acid lipase activity than DU and LW(E) sires and also a lower neutral esterase activity than LW(E) and LW(D) sires. Significant differences between sexes were found for cathepsin H activity only, being higher for females.

Relationships between meat quality measurements in rabbits fed with three diets of different fat type and content.

Two hundred and eighty-four, genetically similar (a three-way cross), young rabbits were fed ad libitum, from weaning, either a commercial diet (group C, ether extract 2.6%) or a diet containing vegetable fat (group V, ether extract, 9.9%) or animal fat (group A, ether extract 11.7%). A principal component (PC) analysis was performed with the variables: ultimate pH at 24 h post mortem measured in the longissimus dorsi (LD) and in the biceps femoris (BF) muscles, colour measured on the surface of the loin, fatty acid composition of perirenal fat, meat fat content of the hind leg, water holding capacity and cooking losses of the meat, and sensory variables determined by a trained panel test. The four first PC explained 62% of the total variation (27, 13, 11 and 11%, respectively). The first PC grouped the fatty acids, the second PC grouped the sensorial variables, and the third and fourth PCs grouped the pHs and the water holding capacity. The projection of the data in the first two PCs showed three separate groups of points. Animals fed with diet V were on the left side of the graph, where the variable C18:2 lies, whereas animals fed with diets A and C lay on the right side of the graph, where the saturated acids were grouped. These were slightly separated by the higher content of oleic acid in the animals fed with diet A. The second PC, where the sensorial variables were grouped, did not separate the animals fed with diets A, V and C. The diets used in this experiment had only a slight influence on the organoleptic characteristics of rabbit meat.

The Effect of Fat-enriched Diets on the Perirenal Fat Quality and Sensory Characteristics of Meat from Rabbits

Two hundred and eighty four medium sized young rabbits were fed ad libitum with two fat-enriched experimental diets (V: vegetable fat, A: animal fat) and a control diet (C). Diet had a significant effect on the ultimate pH (pHu) of the Longissimus dorsi muscle and on the colour, weight and fatty acid composition of the perirenal fat. The carcasses from diet C had significantly less perirenal fat (14.2 g) compared to the carcasses from group A and V (24.4 and 23.0 g) using carcass weight and age of the animals as covariables. Supplementing the diet with animal fat produced perirenal fat which was richer in oleic acid (41%) than in groups V (20.9%) and C (27.9%). The P:S ratio was higher in group V (2.45) compared with groups A and C (0.53 and 0.42). Diet also affected the organoleptic quality of the loin meat. The meat from groups V and C was considered to have a more aniseed flavour than that from group A. In contrast the loin meat from group A had more liver flavour. Both groups V and A were considered juicier than group C. No differences were found in hardness, chewiness and fibrousness. These results suggest than from a human health point of view, the use of a diet supplemented with animal fat is useful on the basis of the nutritional index, P:S of the perirenal fat. However the amount of fat added in the diets V and A should be less than used in this study if the carcass is sold whole in order to avoid excessive perirenal fat. From an organoleptic point of view, the greater aniseed and grass flavour of group V compared to group A may give meat of better sensory quality.

Effect of selection for growth rate on the ageing of myofibrils, meat texture properties and the muscle proteolytic potential of m. longissimus in rabbits.

The effect of selection for growth rate on the degradation of the myofibrillar proteins and on meat texture properties of rabbit longissimus muscle at two ageing times (1 and 7 days) was studied as well as its effect on the proteolytic potential of the muscle. Two groups of contemporary animals (20 rabbits per group), one selected for growth rate (S) for 14 generations and the other unselected control group (C) were compared. The control group was formed from the offspring of the embryos belonging to the 7th generation and was compared with selected animals belonging to 21st generation. Myofibrillar protein degradation was studied by SDS-PAGE electrophoresis (12.5% and 4-15% polyacrylamide gels) followed by densitometric analysis of the pherograms. Texture properties were evaluated by Warner-Bratzler (WB) test and Texture profile analysis (TPA). The activities of proteolytic enzymes calpains and cathepsins and of their inhibitors were determined in the muscle at 24h. Densitometric analysis of the pherograms of samples aged 7 days showed an extra 30kDa band and the disappearance of a band with higher molecular weight than the myosin heavy chain with respect to samples aged 24h in both groups of rabbits. TPA results showed that cohesiveness was significantly lower in meat at 7 days than at 24h (P<0.0001), whereas springiness and chewiness presented a clear tendency to be lower at 7 days than at 24h (P=0.0646 and P=0.0764, respectively). Regarding the genetic type, S animals presented higher hardness and chewiness than C rabbits. Shear firmness (WB test) was significantly (P<0.0001) higher for S group, whereas no significant differences in shear force and area were found. No significant effect (P>0.05) of ageing time was detected using WB test. Selection for growth rate did not affect the activities of proteolytic enzymes or their inhibitors.

Effect of selection for growth rate on relative growth in rabbits.

The effect of selection for growth rate on relative growth of the rabbit body components was studied. Animals from the 18th generation of a line selected for growth rate were compared with a contemporary control group formed with offspring of embryos that were frozen at the seventh generation of selection of the same line. A total of 313 animals were slaughtered at 4, 9, 13, 20, and 40 wk old. The offal, organs, tissues, and retail cuts were weighed, and several carcass linear measurements were recorded. Huxleys allometric equations relating the weights of the components with respect to BW were fitted. Butterfields quadratic equations relating the degree of maturity of the components and the degree of maturity of BW were also fitted. In most of the components studied, both models lead to similar patterns of growth. Blood was isometric or early maturing and skin was late maturing or isometric depending on the use of Huxleys or Butterfields model. Full gastrointestinal tract, liver, kidneys, thoracic viscera, and head were early maturing, and the chilled carcass and reference carcass were late maturing. The retail cuts of the reference carcass showed isometry (forelegs) or late maturing growth (breast and ribs, loin, hind legs, and abdominal walls). Dissectible fat of the carcass and meat of the hind leg had a late development, whereas bone of the hind leg was early maturing. Lumbar circumference length was later maturing than the carcass length and thigh length. Sex did not affect the relative growth of most of the components. Butterfields model showed that males had an earlier development of full gastrointestinal tract and later growth of kidneys than females. No effect of selection on the relative growth of any of the components studied was found, leading to similar patterns of growth and similar carcass composition at a given degree of maturity after 11 generations of selection for growth rate.

Comparison between rabbit lines for sensory meat quality

Rabbits from three synthetic lines were used in the experiment. Line R was selected for growth for 24 generations. Lines V and A were selected for litter size at weaning for 30 and 33 generations, respectively. Sensory analysis was carried out on the Longissimus muscle. The parameters evaluated were: juiciness (J), hardness (H), fibrousness (F), flouriness (Fl), intensity of rabbit flavour (IRF), aniseed odour (AO), aniseed flavour (AF), liver odour (LO) and liver flavour (LF). A Bayesian analysis was performed. Line V was only 82% as juicy as line R. Line V was 18% harder and 17% more fibrous than line R. Lines A and R had the same H and F. No differences in Fl were found. Small effects were found for flavour traits. We conclude that line origin has an influence on some sensory traits determining rabbit meat tenderness.