Livestock Research for Rural Development 20 (5) 2008 Guide for preparation of papers LRRD News

Citation of this paper

Comparing Saudi synthetic lines of rabbits with the founder breeds for carcass, lean composition and meat quality traits

A M Al-Saef, M H Khalil, S N Al-Dobaib, A H Al-Homidan, M L Garca and M Baselga**

Department of Animal Production and Breeding, College of Agriculture and Veterinary Medicine, Al-Qassim University, Buriedah 51452 P.O.Box 6622, Saudi Arabia
*Divisin de Produccin Animal, Departamento de Tecnologa Agroalimentaria, Universidad Miguel Hernndez, Ctra Beniel Km. 3.2 Orihuela 03312, Alicante Spain
**Departamento de Ciencia Animal, Universidad Politecnica de Valencia, Camino de Vera 14, Apdo 22012, 46071, Spain
maherhkhalil@yahoo.com

Abstract

An evaluation for five-year crossbreeding project was performed for pre-slaughter weight (PSW), weights of hot carcass (HCW) and offal (OW) as edible carcass, dressing percentages (DP), weights of head (HW), fur (FURW), lung (LW) and viscera (VW) as non-edible carcass traits, weights of meat (MW), bone (BW) and fat (FW) as tissues composition and percentages of dry matter (DM), crude protein (CP), ether extract (EE) and ash in the lean as meat quality traits. This crossing project involving a Spanish maternal line called V-line (V) and a Saudi Gabali (S) rabbits and 14 genetic groups of V, S, VS, SV, VS, SV, (VS)2, (SV)2, (VS)2, (SV)2, ((VS)2)2, ((SV)2)2, Saudi 2 (synthesized maternal line), and Saudi 3 (synthesized paternal line) were produced in this project. A total number of 2770 rabbits fathered by 91 sires and mothered by 402 dams were slaughtered. Heritability and common litter effects were estimated using an animal model and  solutions of the mixed model equations for the genetic group effects were estimated to identify the possibilities of using Saudi 2 and Saudi 3 as synthetic lines in hot climate areas.

 

Heritability estimates were mostly moderate and ranging from 0.17 to 0.22 for edible carcass traits, 0.12 to 0.22 for non-edible carcass traits, 0.14 to 0.20 for lean composition traits, and 0.12 to 0.36 for meat quality traits. For common litter effects, the estimates were mostly moderate or high and ranging from 0.31 to 0.35, 0.29 to 0.39, 0.15 to 0.29, and 0.17 to 0.23, respectively. Relative to line V or Saudi Gabali, Saudi 2 (with of its genes coming from line V) and Saudi 3 (with only of its genes coming from line V) were mostly significantly superior in PSW, edible carcass (HCW, OW), DP, non-edible carcass (HW, LW, VW), tissues composition (MW, BW), MBR, and meat quality traits (DM, EE and ash). In most cases, the estimates for Saudi 2 were found to be significant ranging from 5.3 to 17.0% for slaughter and edible carcass traits, from 9.7 to 18.1% for non-edible carcass traits, 7.5 to 15.1% for tissues compositions, and 3.8 to 39.2 % for meat quality traits comparable to purebred Saudi rabbits, while the estimates for Saudi 3 ranged from 8.6 to 18.6%, 11.7 to 18.8%, 8.5 to 13.9%, and 3.2 to 47.1%, respectively.

 

In practice, both Saudi 2 and Saudi 3 could be used as specialized synthetic lines convenient for hot climate countries since they were significantly superior in carcass performance, lean composition and meat quality traits relative to the founder lines.

Key words: animal model, carcass, common litter effects, heritability, meat quality, rabbits, synthetic lines


Introduction

Genetic improvement strategies could considerably increase growth and meatiness in the rabbits (Pla et al 1998; Piles et al 2000). In fact, current selection programmes in most parts of the world are selecting for fast growth rates and use of terminal sires, with the goals to improve growth and carcass efficiency (Feki et al 1994; Lobera et al 2000; Snchez et al 2004). In developed countries, using crossbred terminal sires for growth and carcass traits is necessary to synthesize new paternal lines (Masoero et al 1985, 1992; Pla et al 1998; Piles et al 2000). In developing countries and in hot climate countries in particular, reports of genetic analyses for carcass traits and meat quality are unfortunately scarce.

 

At the beginning of this decade (2000), a co-operative rabbit project was established between Saudi Arabia and Spain to synthesize new lines of rabbits adaptable for hot climate. Some traits in this project such as litter, lactation, feeding and semen traits have been genetically evaluated (Khalil et al 2004; Khalil et al 2005), while others such as carcass and meat quality traits have not. The objectives of the present study were (1) to estimate heritabilities, common litter effects and random error effects for carcass and meat quality traits in a crossbreeding program involving one Saudi breed and one Spanish line of rabbits, that are the founders of the new lines, and (2) to evaluate carcass performance and meat quality of the two new maternal and paternal lines of rabbits synthesized. These synthetic lines have now reached the 7th generation of selection for litter weight at weaning and individual weight at 84 d using a BLUP methodology under an animal model.

 

Materials and methods 

Crossbreeding plan and management

 

A five-year crossbreeding project was started in September 2000 in the Experimental Rabbitry, College of Agriculture and Veterinary Medicine, Qassim University to develop new maternal and paternal lines of rabbits.  Rabbits used in this project represent one desert Saudi Gabali breed (S) and one exotic Spanish breed (V-line). The Spanish V-line rabbits used in this project were imported from Valencia Polytechnic University in Spain to be crossed with Saudi Gabali rabbits. Such maternal V-line was selected in Spain for number of young weaned per litter since 1984 using BLUP with a repeatability animal model and non-overlapping generations (Estany et al 1989). Details of the procedures and crossbreeding plan used in the project to form these synthetic lines were described by Khalil et al (2005, 2007). The crossbreeding plan permitted simultaneous production of 14 genetic groups as shown in Table 1.

 

The rabbits were managed with natural mating in a semi-closed rabbitry. In the rabbitry, the environmental conditions were monitored; temperature ranged from 20 to about 32C, relative humidity ranged from 20 to 50%, and the photoperiod in hours was 16 h light: 8 h dark. At four weeks of age, young rabbits were weaned, ear tagged, weighed, sexed and reared in progeny wire cages equipped with feeding hoppers and drinking nipples. Rabbits were fed a commercial pelleted diet during the whole period. On a dry matter basis, the commercial pelleted diet contained 17.9% crude protein, 15.57% crude fiber, 2.45% ether extract, 58.5 nitrogen free extract, and 6.29% ash.

 

Data set

 

Data used in this study were recorded from November 2000 until July 2005. At 12 weeks of age, rabbits representing 14 genetic groups were randomly slaughtered to obtain carcass traits. A total of 2770 rabbits from 91 sires and 402 dams were slaughtered. The numbers of rabbits slaughtered from each genetic group are presented in Table 1. According to criteria and terminology for carcass traits and lean composition cited by Blasco et al (1993), rabbits were dissected for edible parts and non-edible ones. Hot carcasses were weighed and dressing percentages were calculated. The head, fur, offal (representing heart + liver + kidneys) and viscera of the carcasses were also weighed. For lean composition traits, all carcasses were divided longitudinally into two similar halves. The right half was separated into lean, fat and bone. Lean of each half was separated and prepared for chemical analysis. Dry matter (using an air-evacuated oven for 16 h), crude protein (Nitrogen x 6.25), ether extract and ash in the lean were determined according to the AOAC (1990).


Table 1.  Genetic groups of the rabbits slaughtered and their sires, dams, and numbers slaughtered at 12 weeks of age for each genetic group

Ordinal number

Rabbit genetic group

Sire
genetic group

Dam
genetic group

Grand-dam group

Rabbits slaughtered

Rabbits chemically analyzed

1

V-line (V)

V-Line

V-Line

V

276

234

2

Saudi (S)

Saudi (S)

Saudi (S)

S

275

232

3

VS

V

S

S

223

203

4

SV

S

V

V

260

216

5

VS

V

SV

V

141

129

6

SV

S

VS

S

204

158

7

(VS)2

VS

VS

S

113

111

8

(SV)2

SV

SV

V

157

145

9

(VS)2

VS

VS

SV

173

155

10

(SV)2

SV

SV

VS

202

198

11

((VS)2)2

(VS)2

(VS)2

VS

197

189

12

((SV)2)2

(SV)2

(SV)2

SV

145

137

13

Saudi 2

((VS)2)2

((VS)2)2

(VS)2

123

122

14

Saudi 3

((SV)2)2

((SV)2)2

(SV)2

281

224

Total

2770

2453


 
Model for analysis

 

The animal model (in matrix notation) used for analysing carcass and meat quality traits was:

y= Xb + Zaua + Zcuc + e

Where:

y = vector of measurements for the slaughtered rabbits,
b = vector of fixed effects of genetic group of slaughtered rabbits (14 levels; see Table 1), and year-season of birth (20 levels), sex, parity order of the doe (5 levels), and litter size in which the rabbits were born (9 levels);
ua = vector of random additive effect of the individual rabbit,
uc = vector of random effects of the litters in which the animal was born;
X, Za and Zc are incidence matrices relating the records to the fixed effects, additive genetic effects, and common litter environmental effects, respectively; and
e is a vector of random residual effects.

 

Variance components of the random effects were estimated by a derivate-free restricted maximum likelihood procedure using MTDFREML software of Boldman et al (1995). Local convergence was considered to be met if the variance of the -2 log likelihoods in the simplex was less than 1x10-6. After first convergence, restarts were made to find global convergence with convergence declared when the values of -2 log likelihood did not change to the second decimal. The inverse of the numerator relationship matrix (A-1) was used with:

 

 

The variance components obtained by the Animal Model were used to solve the corresponding mixed model equations, obtaining solutions for the genetic group means and their standard errors, using the PEST program (Groeneveld 2006).

 

Results and discussion 

Actual means and variations

 

Results in Table 2 describe the performance of carcass and meat quality traits for rabbits raised in this project.


Table 2.  Summary statistics for carcass and meat quality traits

Trait

 

Mean

Standard deviation

Minimum

Maximum

Item

Abbreviation

Pre-slaughter weight, g

PSW

2482

306

1442

3390

Edible carcass traits:

 

 

 

 

Hot carcass weight, g

HCW

1381

201

709

2024

Dressing percent, %

DP

55.5

2.9

40.9

65.0

Offal weight, g

OW

100.1

22.2

54.0

209

Non-edible carcass traits:

 

 

 

 

Head weight, g

HW

224

25

122

293

Fur weight, g

FW

236

42

113

349

Lung weight, g

LW

104

15

60

192

Viscera weight, g

VW

398

67

100

593

Tissues composition in the carcass:

 

 

 

Meat weight, g

MW

1041

153

550

1496

Bone weight, g

BW

271

59

112

518

Fat weight, g

FW

28.9

16.1

1.9

93.3

Meat to bone ratio

MBR

3.98

0.87

2.3

9.1

Meat quality traits:

 

 

 

 

Dry matter, %

DM

28.7

1.9

22.3

36.0

Crude protein, %++

CP

76.1

5.8

46.9

91.2

Ether extract, %++

EE

15.0

5.9

1.1

49.9

Ash, %++

Ash

9.0

4.1

1.3

18.2

+Dressing percentages = (HCW/PSW)x100.;  Traits expressed on dry matter basis.


Slaughter weight of the rabbits of this experiment ranged from 1442 to 3390 g with an average of 2482 g, while hot carcass weight ranged from 709 to 2024 g with an average of 1381 g (Table 2). Estimates revised by Colin (1999) indicate that carcass weights are varied from one country or region to another to be ranged from 1.0 to 1.8 kg. Ozimba and Lukefahr (1991) in USA observed a mean of 1.02 kg for hot carcass when rabbits were slaughtered at 2.02 kg. For hot carcass weight of New Zealand White rabbits raised in Egypt, Ayyat et al (1994) and Marais et al (1996) reported lower value of 1291 and 1150 g, respectively.

 

The dressing out percentage averaged 55.5 % across all genetic groups (Table 2). This percentage is comparable to Afifi et al (1994) in Egypt for rabbits slaughtered at 12 weeks of age, while Ozimba and Lukefahr (1991) in USA and Feki et al (1994) and Lobera et al (2000) in Spain obtained higher values for dressing out percentages in rabbits slaughtered at 71 or 63 days of age. These variations may be attributed to that breeds and times of slaughter used in each experiment were different, the change in allometric coefficients and the carcass yield seems to be increased until 91 days (Dalle Zotte and Ouhayoun 1995). Szendr et al (1996) in Hungary found that the best dressing percentages were obtained from rabbits weighted in the range from 3.2 to 3.4 kg.

 

Meatiness expressed as meat bone ratio was 3.98 (Table 2). Szendr et al (1996) in Hungary found that the best ratios of meatiness were obtained from rabbits weighted in the range from 3.2 to 3.4 kg. Pla et al (1998) found that meat-bone ratio of V line was 4.56 when the rabbits were slaughtered at nine weeks of age.

 

Fatness expressed as percentage of dissectible fat (28.9g) across all genetic groups was found to be 2.1 % relative to the hot carcass weight (Table 2).  For fatness, Feki et al (1994) in Spain reported values of 15.9 and 5.3 g of perirenal fat weight and scapular fat weight for V line rabbits slaughtered at an average weight of 2033 g. Blasco and Ouhayoun (1993) indicated that the percentage of dissectible fat ranged from 3 to 6% of the carcass.

 

Data corresponding to meat quality traits are described in Table 2. A total of 2453 rabbits were dissected to be chemically analysed. On dry matter basis, figures of meat quality gave an impression to that rabbit meat could be appreciated for its high nutritional and dietetic properties since ether extract in the lean was low (15.0%) and protein content was high (76.1%) as shown in Table 2. Pla et al (1998) chemically analysed four carcass portions in V-line rabbits and found that fat percent in foreleg, Longissimus dorsi, abdominal wall, and hind leg was 6.89%, 0.90%, 5.66% and 3.45%, respectively, but the slaughter weight in their study was lower than here, while the protein was always lower than the values in our study; no matter the carcass portions. However, Parigi Bini et al (1992) reported that meat rabbit are high in unsaturated lipids (60%), high in amino acids of high biological values, poor in cholesterol and sodium, and rich in potassium, phosphorous and magnesium.

 

Heritability estimates

 

Heritability estimates for edible and non-edible carcass, lean composition and meat quality traits were mostly moderate (Table 3). The estimates ranged from 0.15 to 0.22 for slaughter and edible carcass traits, from 0.12 to 0.22 for non-edible carcass traits, from 0.14 to 0.20 for carcass compositions traits, and from 0.12 to 0.36 for meat quality traits. Heritabilities estimated by Ayyat et al (1994) for non-edible carcass traits for NZW rabbits raised in Egypt were low to moderate. In Brazil, Ferraz and Eler (1996) reported moderate estimates of heritability for carcass weight and carcass yield of 0.178 and 0.152 for the Californian breed and 0.152 and 0.000 for New Zealand White rabbits, respectively. Heritability estimated by Lukefahr et al (1996) in USA for carcass yield and lean-to-bone ratio were 0.37 and 0.35 for rabbits selected for 70-day body weight.


Table 3.  Estimates of the proportion of the phenotypic variance due to additive genetic effects (h2) and to common litter effects (c2) and to random error effects (e2) with standard errors (SE) for carcass and meat quality traits

Trait

h2SE

c2SE

e2SE

PSW

0.150.060

0.370.035

0.480.044

Edible carcass traits:

 

 

HCW

0.220.069

0.320.036

0.460.049

DP

0.170.078

0.350.036

0.480.055

OW

0.170.069

0.310.037

0.520.049

Non-edible carcass traits:

 

 

HW

0.220.068

0.340.037

0.440.048

FURW

0.120.060

0.310.034

0.570.045

LW

0.130.051

0.390.033

0.480.038

VW

0.220.071

0.290.037

0.490.036

Carcass composition traits:

MW

0.170.064

0.290.035

0.530.047

BW

0.190.066

0.210.033

0.600.049

FW

0.140.063

0.260.034

0.600.047

MBR

0.200.067

0.150.032

0.660.049

Meat quality traits, DM basis, %

 

 

DM

0.360.084

0.210.040

0.430.059

CP

0.250.084

0.210.041

0.540.061

EE

0.120.070

0.230.037

0.650.052

ASH

0.130.029

0.170.025

0.700.012


Common litter effects

 

Estimates of common litter effects for carcass traits, carcass composition and meat quality traits were moderate to high and were always higher than the respective heritabilities (Table 3). The estimates ranged from 0.31 to 0.37 for slaughter and edible carcass traits, 0.29 to 0.39 for non-edible carcass traits, 0.15 to 0.29 for composition traits, and 0.17 to 0.23 for meat quality traits. Common litter effects appeared to have strong effects on growth even up to slaughtering time. However, estimates heritabilities and common litter effects for carcass and meat quality traits (P<0.05 or P<0.01; Tables 4 and 5) obtained in this study were generally smaller than estimates available in the literature (e.g. Ferraz et al 1992; Lukefahr et al 1996). Ferraz et al (1992) reported common environmental effects to be consistently more important than direct genetic effects for growth traits studied, but Lukefahr et al (1996) indicated that for each carcass trait investigated, the magnitudes of direct genetic and common environmental effects were similar.

 

Comparing line V with Saudi Gabali

 

Edible and non-edible carcass traits and lean composition produced from V-line rabbits were mostly better than from Saudi rabbits as V-line rabbits had significantly heavier PSW, HCW, OW, HW, FURW, LW, MW, BW, with the richest meat in DM and ash (Tables 4 and 5). The superiority for V-line rabbits was expected and reflect the superiority of this line for growth and survival (Estany et al 1989; Pla et al 1996; Garcia et al 2000a,b). These results suggest the necessity to identify the genetic effects for growth and carcass performances in Saudi rabbits taking into account the genetic association between carcass traits and growth performance. 


Table 4. Estimates of differences of the effects of lines V, Saudi 2 (S2) and Saudi 3 (S3) relative to Saudi Gabali breed (S) for carcass and meat quality traits

Doe trait+

Line V vs Saudi (V-S)

Saudi 2 vs Saudi  (S2-S)

Saudi 3 vs Saudi (S3 –S)

Estimate SE

%++

Estimate SE

%++

Estimate SE

%++

PSW

19729*

7.9

30048**

11.5

33443**

12.7

Edible carcass traits:

 

 

 

 

 

HCW

20019**

14.0

25145**

17.0

28129**

18.6

DP

4.00.2**

7.0

3.00.6*

5.3

5.00.4**

8.6

OW

202.0**

18.1

82.7*

8.1

123.1*

11.7

Non-edible carcass traits:

 

 

 

 

 

HW

182.4*

8.0

275.6*

11.5

293.6**

12.2

FURW

243.9*

10.0

325.4*

12.9

316.1*

12.6

LW

101.3*

9.5

213.1**

18.1

222.0**

18.8

VW

226.1ns

5.6

408.4*

9.7

499.2*

11.7

Tissues composition in the carcass:

 

 

 

 

MW

11814*

11.3

13134*

12.4

14922**

13.9

BW

285.2*

9.9

4513.2*

15.1

368.4*

12.4

FW

-1.11.48ns

-4.4

2.13.67ns

7.5

2.42.34ns

8.5

MBR

-0.510.07*

-13.2

0.520.19*

12.0

0.480.12*

11.0

Meat quality traits, DM basis (%):

 

 

 

 

DM

-2.80.45*

-11.6

2.20.25*

8.2

2.30.57*

8.6

CP

-4.03.0ns

-6.4

2.67.7ns

3.8

2.10.49ns

3.2

EE

-1.10.07ns

-7.5

-4.402**

-39.2

-5.00.12**

-47.1

Ash

-0.80.39*

-9.7

1.80.85**

16.6

1.30.55**

12.6

+See table 2; ++ Estimates expressed as percentages relative to Saudi breed
NS= P>0.05; *= P<0.05; ** = P<0.01



Table 5.  Estimates of differences of the effects of Saudi 2 (S2) or Saudi 3 (S3) lines relative to line V and Saudi 3 relative to Saudi 2 for carcass and meat quality traits

Doe trait+

Saudi 2 vs line V (S2-V)

Saudi 3 vs line V (S3-V)

Saudi 3 vs Saudi 2 (S3-S2)

Estimate SE

%++

Estimate SE

%++

Estimate SE

%

PSW

10319*

4.1

13714*

5.5

345ns

1.4

Edible carcass traits:

 

 

 

 

 

HCW

10116*

7.1

8110*

5.7

-2016ns

1.4

DP

-1.50.3ns

-2.6

1.00.4ns

1.7

2.00.2ns

3.5

OW

-121.7*

-10.9

-8.01.1*

-7.3

4.00.8ns

4.1

Non-edible carcass traits:

 

 

 

 

 

HW

9.02.8*

4.0

11.01.2ns

4.9

2.02.0ns

0.9

FURW

8.05.5ns

3.8

7.02.8ns

2.9

-1.03.3ns

0.4

LW

112.8*

10.5

120.7*

11.4

1.01.1ns

1.0

VW

184.4ns

4.6

273.0*

6.9

9.05.2ns

2.2

Tissues composition in the carcass:

 

 

 

 

MW

1310ns

1.2

3118.0ns

3.0

18.012.0ns

1.7

BW

172.0*

6.0

85.2ns

2.8

-9.04.8ns

3.2

FW

3.21.0*

13.1

3.50.9*

14.2

0.31.34ns

1.2

MBR

1.030.08**

26.8

0.990.09**

25.8

0.040.07ns

1.0

Meat quality traits, DM basis (%:

 

 

 

 

DM

5.00.92**

20.7

5.10.91**

21.2

0.10.95ns

0.4

CP

6.61.3*

10.7

6.11.2*

9.9

-0.51.9ns

-0.8

EE

-3.30.2**

-22.8

-3.91.1**

-26.9

-0.60.5ns

-4.1

Ash

2.60.42**

31.7

2.10.14**

25.6

-0.50.16ns

-6.1

+See table 2; ++ Estimates expressed as percentages relative to line V.

NS= P>0.05; *= P<0.05; ** = P<0.01


Comparing synthetic Saudi 2 and Saudi 3 lines with the founder breeds

 

In order to evaluate the results of the two lines synthesized (Saudi 2 and Saudi 3), a comparison between these lines and line V and Saudi Gabali was carried out. The results of tests of differences between them obtained from the solutions of the mixed model equations for genetic group effects have shown in Tables 4 and 5.  These solutions were used to identify the possibilities of using these rabbits as synthetic lines or not. However, Saudi 2 and Saudi 3 were superior for the majority of edible and non-edible carcass traits, carcass composition and meat quality traits.

 

Results of the two synthetic lines developed in the present study have shown that Saudi 2 (with of its genes coming from line V) and Saudi 3 (with only of its genes coming from line V) were significantly superior in edible and non-edible carcass traits relative to line V or Saudi Gabali (Tables 4 and 5). Analyses of crossbreeding experiments carried out in the Arabian countries (e.g. Afifi et al 1994; El-Deghadi 2005) showed much less estimates in carcass traits than for the two synthetic lines developed here. Bianospino et al (2004a,b) in Brazil recommended that crossbred rabbits could be used to produce retail cuts and carcass because they would have heavier carcasses and loins without increased fatness. Metzger et al (2004b) in Hungary with Pannon White (P), Pannon Ka (PK), Hycole (H), Zika (Z) rabbits and their crossbreds reported that the most important carcass traits in P rabbits had an advantage.

 

Estimates for tissues composition in the carcass (MW, BW, FW, and MBR) were mostly in favour of Saudi 2 and Saudi 3 relative to the founder breeds (Tables 4and5). MBR was greater with earlier maturity and consequently synthetic rabbits had greater MBR than V-line rabbits (Pla et al 1996). Although the fat content of the carcass in rabbits is low relative to other animals, fat deposited in the carcass of the synthetic rabbits was greater than that in V-line rabbits (Table 5). However, fat deposits increases with age. Similar breed differences in fat deposited in the carcass have been found by Gomez et al (1998) and Metzger et al (2004a,b). Pla et al (1996) in Spain stated that R-line rabbits had fat percentages higher than line V. Metzger et al (2004a) in Hungary found that MBR in four genetic groups of Hyplus hybrid, Pannon White rabbits and their crossbreds were nearly similar (about 2.7). In another experiment in Hungary, Metzger et al (2004b) using Pannon White (P), Pannon Ka (PK), Hycole (H), Zika (Z) rabbits and their crossbreds reported significant differences among genetic groups for fat content of the carcass (P<0.05) were the  early-maturing genetic groups were PK (1.8%) and P (1.8%).

 

Estimates for DM, CP, EE and ash contents in the lean were mostly in favour of synthetic lines relative to the founder breeds (Tables 4 and 5). In Hungary, Metzger et al (2004a) with four genetic groups found that differences in protein and ash contents of the lean.

The estimates for Saudi 2 relative to purebred Saudi rabbits were greatly deviated by values ranging from 5.3 to 17.0% for slaughter and edible carcass traits, from 9.7 to 18.1% for non-edible carcass traits, 7.5 to 15.1% for tissues compositions, and 3.8 to 39.2 % for meat quality traits (P<0.05 or P<0.01; Tables 4and5)). In comparison with purebred V-line, the corresponding estimates were slightly greater by 2.6 to 10.9 % for slaughter and edible carcass traits, by 3.8 to 10.5 % for non-edible carcass traits, by 1.2 to 26.8 % for carcass composition traits, and by 10.7 to 31.7 % for meat quality traits.

 

Comparing Saudi 3 with purebred Saudi rabbits, the estimates were widely deviated by differences ranging from 8.6 to 18.6 % for slaughter weight and edible carcass traits, 11.7 to 18.8 % for non-edible carcass traits, 8.5 to 13.9 % for carcass composition traits and 3.2 to 47.1 % for meat quality traits. Comparable to purebred V-line rabbits, the corresponding percentages ranged from 1.7 to 7.3 %, 2.9 to 11.4 %, 2.8 to 25.8 %, and 9.9 to 26.9 %.

 

Comparing Saudi 3 with Saudi 2, the estimates for both lines were nearly similar with no significant differences between them in all traits studied (Table 5).

 

Offal of the synthetic line rabbits was less in weight than V-line rabbits (Table 5). Liver and heart (offal) are organs of early development and animals with high growth rate have an earlier development (Gomez et al 1998). Gomez et al (1998) found that liver and heart weights for rabbits of line R were heavier than for line V. Results in the literature comparing breeds of large-size with small-size breeds and straightbreds with crossbreds for carcass traits are not consistent (Lukefahr et al 1982, 1983; Ozimba and Lukefahr 1991; Pla et al 1996; Bianospino et al 2004a,b) because measurements were made at different slaughter weights but differences can be partially due to true genetic differences between breeds.

 

Conclusions  

 

Acknowledgment

This project is supported by a grant (ARP: 18-62) from King Abdulaziz City for Science and Technology in Saudi Arabia.

 

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Received 22 October 2007; Accepted 27 November 2007; Published 1 May 2008

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