characteristics, and meat quality in pigs and relationship between

Federal Department of Economic Affairs FDEA

Agroscope Liebefeld-Posieux ALP Research Station ALP Milk and meat production

Effect of litter size and birth weight on growth performance, carcass

characteristics, and meat quality in pigs and relationship between

proteolysis post-mortem and pork quality traits

Joël Bérard

21 may 2007 Qualifying Exam for Doctoral Studies

Preface 2

Increasing the number of the piglets born per litter:

• Increasing ovulation rate, embryonic survival and uterine capacity.

• including hyperprolific female into breeding nucleus.

(in Switzerland litter size has increased from less than 10.9 to 11.8 piglets per litter –Annual Report Suisag, 2005-)

Genetic selection strategy in the last decade

Problem:

• Increasing of litter size leads to a decrease in birth weight especially in piglets with low birth weight

(Foxcroft, 2007).

• low birth weight pigs not only grow slower and have worse carcass characteristics but also worse meat quality traits than their high birth weight siblings

(Bee, 2004; Bee et al., 2006a; Gondret et al., 2005b; Gondret et al., 2006a; Quiniou et al., 2002; Rehfeldt and Kuhn, 2006).

For economic reason

3

Myogenesis

important aspect for post-natal growth performance, carcass and meat quality

Biphasic phenomenon:

• 1

phase: development of primary fibers (from 35 to 55 d of gestation).

• 2

phase: formation of secondary myofibers using the primary as scaffold (until 90 d of gestation).

Preface

1. Hyperplasia (increasing myofiber numbers):

ceases at 90 d of gestation.

2. Hypertrophy (increase of size of myofibers):

during all post-natal growth.

Myogenesis

important aspect for post-natal growth performance, carcass and meat quality

Introduction 4

This hypothesis has been suggested because:

Intrauterine crowding leads to:

→ poor placenta development

→ increasing of fetus competition for maternal nutrients

→ consequently poorer growth performance, carcass characteristic, and meat quality at slaughter

(Foxcroft, 2007).

Prenatal programming effects:

• muscle development

• muscle growth

• influences the risk of postnatal diseases (Foxcroft, 2007).

1 ^st Aim of the study

was to test the hypothesis that effects of Birth weight (BtW) on:

growth performance carcass characteristics meat quality

differ when pigs originate from small or large litters.

Introduction 5

Investigation of the relationship between post-mortem proteolysis:

Birth weight Litter size

Meat quality traits

2 ^nd Aim of the study

Different studies have reported:

correlations importance

of the post-mortem proteolysis and meat quality traits

(Kristensen and Purslow, 2001; Melody et al., 2004; Zhang et al., 2006;

Lametsch et al., 2003; Lawson, 2004; Lametsch et al., 2002; Bee et al., 2006b).

Few studies have been carried out considering a so large pattern:

protein degradations enzyme activities

relationships to meat quality traits .

6

Litter size

20 litters from multiparous Swiss Large White sows

• Large litter size : 10 litters with ≥ than 14 piglets born/litter

• Small litter size : 10 litters with ≤ than 10 piglets born/litter

Experimental design

Introduction

Birth weight

From within small and large litter, 60 barrows were selected with:

• Lightest birth weight (L-BtW)

• Nearest to the average birth weight (M-BtW)

• Heaviest birth weight (H-BtW)

Growth performance 7

Influence of litter size on birth weight

0.50 1.00 1.50 2.00 2.50

L-BtW M-BtW H-BtW

Kg

Large litter size Small litter size

Factor P-value

LS 0.02

BtW <0.01 BtW * LS 0.07

At weaning, the barrows were individually penned.

They had free access to standard diets:

• starter (9 – 27 kg BW),

• growing (27 – 63 kg BW)

• finishing (63 - 105 kg BW) until slaughter (105 Kg).

The BW and total feed intake was determined each week.

• Increasing litter size the percentage of L- BtW pigs is higher

• The birth weight of small piglets is markedly lower.

In L-litters, L- and M-BtW barrows were more affected by lower nutrient supply during gestation than H-BtW barrows.

In agreement with our findings, Quiniou et al. (2002) reported that average birth weight of the litter is lower in large compared to small litters

.

Factor P-value

LS 0.02

BtW <0.01

BtW * LS 0.07

Growth performance 8

The observed differences were in agreement with results of previous studies.

(Bee et al., 2006a; Gondret et al., 2005b; Rehfeldt and Kuhn, 2006).

Direct correlations between BtW and fiber number (Rehfeldt and Kuhn, 2006).

Fiber number is fixed at birth (Rehfeldt and Kuhn, 2006).

Trait L-BtW M-BtW H-BtW SEM

L-LS S-LS SEM

ADWG (kg/d)

0.81 0.89 0.90 0.016

0.88 0.86 0.016 0.47

ADFI (kg/d)

2.30 2.40 2.43 0.040

2.40 2.36 0.041 0.49

FCR (kg/kg)

2.84 2.72 2.70 0.031

2.75 2.76 0.033 0.89

TFI (kg)

218 207 208 2.6

211 211 2.9 0.98

Age (d)

170 159 158 2.5

163 162 2.4 0.95

9

Trait L-BtW M-BtW H-BtW SEM P-value L-LS S-LS SEM P-value

Hot carcass weight 86.2 85.4 85.8 0.04 0.44 86.0 85.6 0.36 0.52 Carcass yield % 82.1 81.6 80.8 0.28 <0.01 81.6 81.4 0.27 0.57 Lean meat % 55.1 54.8 55.4 0.47 0.65 54.7 55.6 0.41 0.15 Omental fat % 2.1 2.0 1.9 0.10 0.54 2.1 1.8 0.10 0.06 Loin % 24.8 24.3 24.7 0.26 0.29 24.4 24.7 0.26 0.35

Ham % 18.1 18.4 18.4 0.19 0.62 18.2 18.4 0.16 0.33

Shoulder % 12.2 12.1 12.3 0.11 0.60 12.1 12.4 0.09 0.02 Belly % 17.4 17.6 17.3 0.24 0.60 17.5 17.4 0.20 0.73 Heart (kg) 0.40 0.41 0.42 0.007 0.23 0.41 0.41 0.007 0.76 Liver (kg) 1.58 1.68 1.74 0.045 0.01 1.65 1.68 0.048 0.64 Kidney (kg) 0.31 0.32 0.34 0.009 <0.01 0.32 0.32 0.011 0.89

Carcass Characteristic

Pigs were slaughtered following standard protocol:

• Electrically stunned

• Exsanguinated

At slaughter, the weights of the hot carcass, heart, liver, and kidney were assessed.

Slaughtering procedure

Barrows from L-litters have a lower protein and a higher fat deposition rate than barrows from S-litters.

Results of carcass yield %, liver and kidney are in accordance to findings of Rehfeldt and Kuhn (2006).

<0.01

<0.01

0.06

0.02

10

Drip loss in STD

2 2.5 3 3.5 4 4.5 5 5.5

H-BtW M-BtW L-BtW

% of drip loss

large litter small litter

Factor P -value

LS 0.77

BtW 0.07 BtW * LS 0.60

measured in the

• Longissimus muscle (LM)

• Dark portion of Semitendinosus muscle (STD) by gravimetric quantification

24 h after slaughter

Drip, thaw, and cook loss

Meat Quality

Drip, thaw and cook loss were no affected by litter size and birth weight in LM.

11

Color

L*, a*, b*, and chroma values for the LM and for STD were measured using a Minolta Chroma Meter.

Meat Quality

• Lightness white color of the meat (L* value).

• Yellowness yellow color of the meat (b* value).

• Redness red color of the meat (a* value).

• Chroma is the color intensity or the degree of color saturation.

12

Trait L-BtW M-BtW H-BtW SEM P-value L-LS S-LS SEM P-value

Longissimus

L*value 49.5 50.4 50.9 0.44 0.09 50.3 50.3 0.37 0.92

a*value 6.9 6.5 6.0 0.21 <0.01 6.6 6.4 0.24 0.58

b*value 3.2 3.0 2.9 0.16 0.45 3.1 3.0 0.16 0.92

Chroma 7.7 7.2 6.7 0.23 <0.01 7.3 7.1 0.27 0.63

Semitendinosus dark

L*value 41.9 42.4 42.8 0.40 0.28 42.4 42.3 0.38 0.97

a*value 14.3 14.4 14.3 0.27 0.92 14.6 14.1 0.22 0.11

b*value 4.9 5.1 5.2 0.20 0.49 5.3 4.9 0.17 0.06

Chroma 15.1 15.3 15.2 0.31 0.85 15.5 14.9 0.25 0.08

Meat Quality

Color results

In LM, H-BtW barrows have more glycolytic fibers than L-BtW barrows (Bee, 2004)

• glycolytic fibers have lower myoglobin content

• which is responsible for the redness of the meat (Lefaucheur, 2001).

In STD, colors were neither affected by BtW but by litter size.

Barrows from large litter had more yellow meat and a higher chroma value than barrows from small litter.

0.09

<0.01

<0.01

0.08 0.06

13

Shear force peak in STD

4.5 5 5.5 6 6.5 7

H-BtW M-BtW L-BtW

Kg

large litter small litter

Factor P -value

LS 0.92

BtW <0.01 BtW * LS 0.34

Shear force

Warner-Bratzler:

• shear force was measured in cooked meat across the fiber direction using a Stable Micro System TA.XT2 Texture Analyzer.

1. LM 10 cores of 1.27 cm diam.

2. STD were cut into 5 strips of 10 x 10 x 30 mm Meat Quality

Data agree with not yet published results from Rehfeldt:

most desirable carcass composition is obtained with H-BtW

optimum pork quality traits are achieved with M-BtW pigs.

Shear force were neither affected by litter size nor by birth weight in LM.

14

pH 24 h post-mortem in STD

5.3 5.5 5.7 5.9 6.1

H-BtW M-BtW L-BtW

pH

large litter small litter

Factor P -value

LS 0.85

BtW 0.06 BtW * LS 0.21

pH

The pH of the LM and in the STD was monitored 30 min, 3 h and 24 h post-mortem

Meat Quality

pH was neither affected by litter size nor by birth weight in LM.

Drip loss Thaw loss Shear force Longissimus

pH 0.5 h -0.36 (P<0.01) -0.29 (P=0.02) 0.01 (P=0.98) pH 24 h -0.50 (P<0.01) -0.30 (P=0.02) 0.36 (P<0.01) Semitendinosus

dark

pH 0.5 h -0.33 (P<0.01) -0.21 (P=0.10) -0.04 (P=0.76)

pH 24 h -0.63 (P<0.01) -0.56 (P<0.01) -0.44 (P<0.01)

15

Proteolysis: an important factor for meat quality description

Light micrographs of muscle samples from low ((a)–(d)) and high ((e)–(h)) drip loss channel in meat samples

Proteolysis

Influence of proteolysis on water holding capacity WHC

2^nd Proteins group (ex: desmin, titin, nebulin) :

• connect cell membrane and myofibrils

• connect myofibrils together

Limited degradation of these proteins

→ transfers the shrinkage on the whole cells

→ increases drip and purge loss (Zhang et al., 2006) 1^st Proteins group (ex: integrin)

• link the extracellular matrix to the cytoskeleton Degradation of β1 integrin:

→increases the drip channel formation

→drip channels contribute to drip loss (Lawson, 2004).

Proteolysis 16

Integrin

• heterodimeric cell adhesion molecule

• 18 α- and 8 β-subunits

• β-Chain integrin is responsible for the attachment of cell membrane to the cell cytoskeleton (Zhang et al., 2006).

Two main functions of integrin are:

Attachment of the cell to the ECM.

Signal transduction from the ECM to the cell.

Integrin was determined in LM and STD collected at 0.5, 24, and 72 h post-mortem with Western blotting method (Bee et al.

2006b) :

1^st step: protein extraction

2^nd step: protein separation (electrophoresis) 3^rd step: transfer from gel to membrane

4^th step: immunoblotting (specific antibody)

17

Relative abudance of integrin 74 h post-mortem

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

H-BtW M-BtW L-BtW

intact int / intact int stand

large litter small litter

Factor P -value

LS 0.08

BtW 0.64 BtW * LS 0.33

Proteolysis

Integrin results

Greater integrin proteolysis was associated with the formation of drip channels (Zhang et al. 2006)

pH 24 h Total drip loss Shear force Longissimus

0.5 h 0.10 (P=0.44) -0.12 (P=0.37) -0.28 (P=0.03) 24 h 0.22 (P=0.09) -0.34 (P<0.01) -0.01 (P=0.93) 72 h 0.02 (P=0.89) -0.16 (P=0.23) 0.21 (P=0.10) Semitendinosus

0.5 h -0.15 (P=0.24) -0.07 (P=0.61) 0.01 (P=0.93) 24 h -0.05 (P=0.69) -0.16 (P=0.22) 0.09 (P=0.47) 72 h -0.07 (P=0.59) -0.31 (P=0.01) 0.08 (P=0.52)

L-litter

S-litter

0.5 h 24 h 72 h

Factor P -value

LS 0.08

BtW 0.64

BtW * LS 0.33

Proteolysis 18

Titin and Nebulin

Titin

• also known as connectin

• connects the Z to the M line in the sarcomere

• limits the range of motion of the sarcomere

• molecular weight 300 KDa Nebulin

• is an actin-binding protein

• is localized to the I-band in skeletal muscle

• is a very large protein (600-900 kDa)

Titin and Nebulin were determined in LM and STD collected at 0.5, 24, and 72 h post- mortem with SDS-PAGE method (Bee et al.

2006b) :

1^st step: protein extraction

2^nd step: protein separation (electrophoresis) 3^rd step: coloration and detection

19

Relative abudance of nebulin 72 h post-mortem in LD

0 0.1 0.2 0.3 0.4 0.5 0.6

H-BtW M-BtW L-BtW

intact neb / intact neb stand

large litter small litter

Factor P -value

LS 0.93

BtW 0.07 BtW * LS 0.12

Relative abudance of titin 24 h post-mortem in LD

0 0.5 1 1.5 2 2.5 3 3.5 4

H-BtW M-BtW L-BtW

intact tit / intact tit stand large litter

small litter

Factor P -value

LS 0.98

BtW 0.06 BtW * LS 0.24

Proteolysis

Titin and Nebulin degradation was neither affected by litter size nor by birth weight of the barrows in STD.

Proteolysis of titin at 24 h post- mortem was greater in LM of H- and M-BtW than LM of L- BtW barrows (P = 0.06).

Nebulin at 72 h was also more degraded in LM of H-BtW than LM of L-BtW and M-BtW barrows (P = 0.07).

Even if meat quality traits were less affected by BtW

these results confirm that protein degradations is impaired in barrows with different BW at birth.

Effect of BtW and litter size on titin and nebulin proteolysis

Proteolysis 20

These correlations are an example of the importance of the proteolysis for a better understanding of the meat quality traits.

Correlations with meat quality traits

pH 24 h Total drip loss Shear force Longissimus

Titin

0.5 h -0.03 (P=0.83) -0.01 (P=0.96) -0.01 (P=0.95) 24 h 0.11 (P=0.42) -0.20 (P=0.13) 0.22 (P=0.09) 72 h -0.03 (P=0.83) -0.14 (P=0.29) 0.23 (P=0.07) Nebulin

0.5 h -0.07 (P=0.62) -0.11 (P=0.38) -0.14 (P=0.30) 24 h 0.07 (P=0.58) -0.01 (P=0.92) 0.05 (P=0.69) 72 h -0.07 (P=0.60) -0.20 (P=0.12) 0.27 (P=0.04) Semitendinosus

Titin

0.5 h -0.12 (P=0.83) 0.25 (P=0.06) 0.21 (P=0.10) 24 h -0.21 (P=0.42) 0.17 (P=0.20) 0.18 (P=0.16) 72 h -0.30 (P=0.02) 0.33 (P=0.01) 0.04 (P=0.75) Nebulin

0.5 h -0.12 (P=0.33) 0.24 (P=0.07) -0.07 (P=0.59) 24 h -0.16 (P=0.22) 0.31 (P=0.02) 0.01 (P=0.93) 72 h -0.23 (P=0.07) 0.20 (P=0.12) -0.21 (P=0.10)

Proteolysis 21

Desmin

Intermediate filament protein:

• ties the myofibrils to the cell membrane

• connects adjacent myofibrils Molecular weight is 55 KDa.

Desmin was determined in LM and STD collected at 24, and 72 h post-mortem with Western blotting method (Bee et al. 2006b) : 1^st step: protein extraction

2^nd step: protein separation (electrophoresis) 3^rd step: transfer from gel to membrane

4^th step: immunoblotting (specific antibody)

Proteolysis 22

Desmin results

Effect of BtW and litter size on desmin proteolysis

Correlations between desmin proteolysis and meat quality traits

Desmin degradation was neither affected by litter size nor by birth weight of the barrows.

Moreover no correlation were found between desmin degradation and meat quality traits.

Desmin results

Effect of BtW and litter size on desmin proteolysis

Values are expressed as intensity of the intact protein band over the intensity of the internal designated densitometry standard.

pH 24 h Total drip loss Thaw loss Shear force Longissimus

24 h -0.13 (P=0.35) 0.01 (P=0.99) -0.05 (P=0.73) -0.05 (P=0.73) 72 h 0.09 (P=0.48) -0.06 (P=0.59) -0.12 (P=0.35) -0.01 (P=0.91) Semitendinosus

dark

24 h 0.07 (P=0.60) -0.02 (P=0.87) 0.10 (P=0.44) -0.08 (P=0.54) 72 h 0.05 (P=0.68) -0.03 (P=0.80) 0.06 (P=0.67) -0.05 (P=0.68)

Trait L-BtW M-BtW H-BtW SEM P-value L-LS S-LS SEM P-value

Longissimus

24 h 1.11 1.13 1.07 0.061 0.69 1.11 1.09 0.061 0.81

72 h 1.11 1.12 1.20 0.078 0.62 1.19 1.10 0.076 0.41

Semitendinosus dark

24 h 1.24 1.38 1.30 0.072 0.33 1.30 1.31 0.069 0.93

72 h 1.36 1.33 1.31 0.074 0.87 1.34 1.34 0.068 0.99

Proteolysis 23

Desmin degradation

Intact desmin

1.0 1.1 1.1 1.2 1.2 1.3 1.3 1.4 1.4 1.5 1.5

24 h 72 h post-m ortem

ratio valuea

STD LD

muscle P -value 24 h <0.01 72 h <0.01

aintensity of the intact protein band over the intensity of the internal designated densitometry standard.

Intact desmin value was higher STD than in LM 24 and 72 h post- mortem.

LD STD

24 72 24 72

H-BtW

M-BtW

• The % of desmin degradation from 24 to 72 h in STD was higher in M-BtW than H-BtW and L-BtW barrows P = 0.09

• STD of M-BtW barrows have tender meat and higher pH value 24 h post-mortem.

Proteolysis 24

Calpains

• Calpains are a family of calcium-dependent thiol-proteases

• The calpain proteolytic system includes:

the calpain proteases

the small regulatory subunit (calpain 4)

the endogenous calpain-specific inhibitor:

calpastatin.

µ- and m calpain activities were determined in LM and STD collected at 0.5, 24, and 72 h post-mortem with casein zymography procedure described by Melody et al. (2004) 1^st step: protein extraction

2^nd step: casein Zymography 3^rd step: detection

Why to investigate Calpain activity?

µ-calpain most important enzyme

• for the post-mortem protein degradation

• for meat tenderization (Geesink et al., 2006)

µ- and m-calpain use the same substrates (Huff-Lonergan and Lonergan, 2005).

Proteolysis 25

µ- and m-calpain activity was neither affected by litter size nor by birth weight of the barrows.

No information about the most important calpain inhibitor:

Calpastatin.

Casein zymography method:

information only about the total potential in vitro activity and not about the actual in vivo activity.

Effect of BtW and litter size on µ- and m-calpain activity

Trait L-BtW M-BtW H-BtW SEM P-value L-LS S-LS SEM P-value

Longissimus m-calpain

0.5 h 0.54 0.52 0.46 0.070 0.64 0.49 0.53 0.064 0.64

24 h 0.23 0.27 0.28 0.041 0.69 0.27 0.25 0.035 0.71

72 h 0.27 0.26 0.30 0.037 0.58 0.30 0.26 0.039 0.49

µ-calpain

0.5 h 2.25 1.93 1.92 0.202 0.41 2.04 2.04 0.176 0.99

24 h 0.76 0.92 0.89 0.130 0.22 0.86 0.79 0.137 0.71

72 h 0.10 0.08 0.08 0.025 0.77 0.11 0.07 0.025 0.15

Semitendinosus dark

m-calpain

0.5 h 0.78 0.61 0.74 0.080 0.26 0.68 0.73 0.071 0.63

24 h 0.19 0.24 0.27 0.045 0.31 0.25 0.22 0.043 0.59

72 h 0.19 0.18 0.25 0.039 0.34 0.22 0.19 0.039 0.58

µ-calpain

0.5 h 2.12 1.72 1.90 0.160 0.22 1.96 1.86 0.131 0.52

24 h 0.67 0.78 0.86 0.105 0.27 0.89 0.65 0.116 0.16

72 h 0.36 0.25 0.36 0.068 0.27 0.37 0.27 0.075 0.39

Proteolysis 26

Both enzymes are important biochemical factors that influence tenderness and water holding capacity

But their activities differ between muscles. (Melody et al. 2004).

Correlation between µ- and m-calpain activity and meat quality traits

Trait Total drip loss Thaw loss Shear force

Longissimus

m-calpain activity

0.5 - 24 h -0.20 (P=0.13) -0.17 (P=0.19) 0.05 (P=0.73) 0.5 - 72 h -0.21 (P=0.10) -0.21 (P=0.11) 0.10 (P=0.43) µ-calpain activity

0.5 - 24 h 0.13 (P=0.30) -0.10 (P=0.43) -0.31 (P=0.01) 0.5 - 72 h 0.01 (P=0.97) -0.21 (P=0.10) -0.20 (P=0.13) Semitendinosus dark

m-calpain activity

0.5 - 24 h -0.21 (P=0.11) -0.10 (P=0.43) -0.01 (P=0.96) 0.5 - 72 h -0.23 (P=0.07) -0.19 (P=0.13) -0.04 (P=0.76) µ-calpain activity

0.5 - 24 h 0.08 (P=0.55) 0.09 (P=0.50) 0.09 (P=0.47)

0.5 - 72 h 0.09 (P=0.48) 0.08 (P=0.52) 0.15 (P=0.24)

Proteolysis 27

µ- and m-calpain are important enzymes for proteins degradation

(Melody et al., 2004; Geesink et al., 2006; Baron et al., 2004; HuffLonergan et al., 1996;

Koohmaraie and Geesink, 2006).

Both isoforms of calpain degrade the same set of myofibrillar and cytoskeletal proteins (Huff- Lonergan and Lonergan 2005).

Correlation between µ- and m-calpain activity and intact proteins

Desmin 24 Desmin 72 Nebulin 05 Nebulin 24 Nebulin 72 Longissimus

m-calpain activity

0.5 - 24 h -0.09 (P=0.48) -0.35 (P<0.01) -0.15 (P=0.25) -0.14 (P=0.29) -0.14 (P=0.28) 0.5 - 72 h -0.10 (P=0.46) -0.43 (P<0.01) -0.08 (P=0.55) -0.14 (P=0.30) -0.12 (P=0.37) µ-calpain activity

0.5 - 24 h -0.07 (P=0.59) -0.26 (P=0.04) -0.16 (P=0.22) -0.32(P=0.01) -0.22 (P=0.09) 0.5 - 72 h -0.04 (P=0.77) -0.18 (P=0.16) -0.24 (P=0.06) -0.30 (P=0.02) -0.32 (P=0.01) Semitendinosus dark

m-calpain activity

0.5 - 24 h -0.31 (P=0.01) -0.22 (P=0.09) -0.22 (P=0.09) -0.29(P=0.02) -0.30 (P=0.02) 0.5 - 72 h -0.27 (P=0.04) -0.21 (P=0.10) -0.15 (P=0.24) -0.28 (P=0.03) -0.33 (P<0.01) µ-calpain activity

0.5 - 24 h -0.14 (P=0.29) -0.03 (P=0.80) -0.20 (P=0.13) -0.28 (P=0.03) -0.09 (P=0.49) 0.5 - 72 h -0.15 (P=0.26) -0.02 (P=0.06) -0.21 (P=0.11) -0.29 (P=0.02) -0.13 (P=0.30)

Conclusions 28

The present results confirm the marked effect of birth weight on growth performance and carcass characteristics.

L-BtW barrows have the lowest post natal growth performance The hypothesized impact on meat quality traits could only be partly demonstrated.

The present study confirms the relationship between protein degradation and some of the important meat quality parameters.

The present findings revealed that the extent of proteolysis influenced differently meat quality traits.

BtW

Litter size affected average birth weight of the L-BtW and M- BtW barrows, but its impact on growth performance, carcass characteristics and meat quality was minor.

Litter size

Proteolysis

Higher integrin degradation is associated with poor meat quality traits

Higher titin and nebulin degradation and calpain activity are associated with better meat quality traits.

Perspectives 29

In the context of this experiment

For further experiments

• investigation of types, cross-sectional area (CSA) and total number of fibers (TNF) in the two muscle to confirm or deny some hypothesis formulated.

• western blot for µ-calpain for a more precise quantification.

• investigation of the number of the fetus at 75 d of gestation and fetus muscles fiber typing for better understanding the influence of the intrauterine crowding.

• 2-dimentional electrophoresis to point out different protein degradations in L- and S-litter.

• to continue the investigation in not only one but many muscle

because they have different meat quality traits and proteolysis.

30

Thank you for your attention

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