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Anatomical study of lesions in destructured ham
E. Laville1, M. Franck2, M. Sidibé1, T. Sayd1, J.M. Bonny1, J.F. Chazeix1 and G. Monin1
INTRODUCTION
Stress occurring in pigs, before and during slaughter favours destructured meat (Franck et al., 2000, 2002). We supposed that a restraint stress provoked by immobilising hind limbs by links during a few minutes should be sufficient to induce destructured meat lesions. This kind of stress may be divided into a phy- sical component (muscular effort) and an emotional component (fear). In order to study the two components separately we compared the effects of immobili- sation by physical links with the effects of immobilization by chemical muscle relaxation. An infusion of succhinylcholine was used to induce leg paralysis without conscience lost. The situation is considered to be emotionaly very pain- ful.
Furthermore, Franck et al. (2000) have shown that pigs carrying the n allele of HAL gene and presenting muscle hypertrophy are more affected by destruc- turation. These two factors were included in the study.
MATERIALS AND ET METHODS
The experimentation was conducted on 40 pigs of three genotypes: Large White x Landrace, Pietrain NN et Pietrain Nn, and two sexes: entire males and females. Animals were transported with as little stress as possible to the experi- mental abattoir 0.5 km far from the farm. They were subjected to four treat- ments: 1,immediate slaughter; 2, infusion of succinylcholine during 12 min prior to slaughter; 3, fetter of four limbs during 12 min prior to slaughter; 4, fetter of four limbs during 12 min followed by 3h of rest before slaughter.
1. ENV-Lyon, 69280 Marcy-l'Etoile.
At 1 hour post mortem, muscle were sampled in the superficial-proximale- caudale area of semimembranosus muscle. Contractile type of muscles was studied by electrophoretic separation of myosin heavy chains (MHCIIB, MHCIIX, MHCI). At 24 hours post mortem, dorsal, lateral and internal surfaces of half- carcasses were photographed. Linear and angular measures were performed on images. The left leg was cut perpendicular to femur bone, into 4 slices of equal thickness (figure 1). The extent of lesions on the four proximal surfaces of slices, was recorded on transparent sheets. Sum of destructured surfaces was related to the sum of total surfaces of the 4 slices.
Transversal development of muscles in the right leg was measured on Nuclear Magnetic Resonance images (CHU Clermont Ferrand). These measures were done at 3 levels of thigh: middle, proximal quarter, distal quarter of femur.
RESULTS
Anatomy of lesions
Colour of destructured meat was pale and its texture was soft and stringy.
Seventeen of the 40 pigs presented destructurations in hams (table 1). Lesions were found in all groups, including control group. Treatments seemed to increase the extent of lesion within the muscles. Pietrain pigs had higher fre- quency of lesions. Lesions were more extended in Pietrain heterozygous Nn pigs than in NN, confirming results of FRANCK et al. (2000).
Table 1
Effect of factors on frequency and extent of destructuration
Factors Size of classes Destructured
hams
Extent of destructuration
treatment
1 12 6 3.3
2 8 5 7.6
3 10 4 7.5
4 10 2 12.3
sex M 13 5 5.2
F 27 12 7.2
genotype
Lw ✕ Ld 16 3 7.5 ab
Pietrain NN 13 6 2.8 a
Pietrain Nn 11 8 9.2 b
ab For each factor, means with different superscripts are different (p<0.05).
Lesions were more developed in proximal part of femur, where muscles are the thickest (figure 1). The most affected muscles were adductor (ad), semi- membranosus (sm) and biceps femoris (bf), in posterior surface of the thigh (figure 2). Lesions were centred around deep femoral vessels and seemed to develop from the red and deep part of muscles (figure 2). Destructuration in muscles of anterior thigh surface was less frequent. Muscles rectus femoris (rf) and vastus lateralis (vl) presented lesions centred around a zone near the vein and artery circonflexe iliaque (figure 3). In gracilis (gr), semitendinosus (st), gas- trocnemius (ga) muscles lesions were less frequent and were observed only in the most destructured hams.
Figure 1
Distribution of lesions in the 4 slices
Figure 2
Frequency of lesions in ham Muscles 600
500 400 300 200 100 0
1 2 3 4
1 2 3 4 Lesion surface
(cm2)
Slice number
0 2 4 6 8 10 12 14 16 18
ad sm bf rf st vl gr ga
Ham muscles Frequency
Figure 3
Localisation of lesions in transversal section of ham
Carcasses morphometry
Differences in carcass and leg conformation measures were observed between the two breeds (LW ✕ Ld and Pietrain). Backs and legs of Pietrains were shorter. Their back was larger. Muscle thickness was higher. Morphologi- cal differences between Pietrains NN et Nn were not significant. Concerning the 17 destructured hams, leg length was negatively correlated to extent of lesions (–0.48).
Biochemical measures
Semimembranosus muscles of Pietrains NN had an higher amount of MHCIIX. We observed a positive correlation (0.57) between amount of MHCI and extent of lesions.
CONCLUSIONS
Treatments before slaughter did not induce destructuration in meat since control animals had an equivalent even superior frequency of lesions than trea- ted animals. On the other end, restraint of animals and succinylcholine infusion seemed to increase the extent of lesions, although differences were not signifi- cant. Genetic factors may increase the frequency and extent of lesions. Extent of lesions was not related to muscle hypertrophy but it was related to leg length.
Anatomical location of lesions near vessels and their positive relationship with slow twitch oxydative fibre type suggest that destructuration can be due to a vascular deficiency.
SM
VL RF AD
ST
BF GR Vessel
Destructured zone Bone
REFERENCES
FRANCK M., MONIN G., LEGAULT C., 2000. J. Rech. Porcine France, 32, 345- 350.
FRANCK M., SVENSSON G., VON SETH G., JOSELL A., FIGWER P., POIREL M.T., MONIN G., 2002. Meat Sci., in press.
This study was realised as part of the programme AQS 00 P0577 of Research Agency « Approches explicatives, diagnostique et préventive des viandes destructurées dans la filière porcine » in collaboration with ITP, CTSCCV and ENV-Lyon (scientific co-ordinator Gabriel Monin, INRA).
