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- ISSN 0189-0514
J. Anim. Prod. Res. (2016) 28(1):104-111
104
HETEROSIS AND MATERNAL EFFECTS FOR CARCASS TRAITS IN THREE BREEDS OF
RABBIT
Kabir1, M., Akpa1, G. N., Nwagu2 B. I. and Adeyinka2 I. A.
1Genetics and Animal Breeding Unit, Department of Animal Science, ABU Zaria, Nigeria
2National Animal Production Research Institute (NAPRI), Shika Zaria, Nigeria
Corresponding Author: mkabir@abu.edu.ng
ABSTRACT
A total of 202, 272 and 256 records for purebred, crossbred and reciprocal-crossbred male and female
rabbits, of three breeds Chinchilla (CHC), Californian White (CAW) and New Zealand White (NZW)
were used in this study. The aim of the study was to estimate maternal, direct additive and heterotic
effects for carcass characteristics in order to identify the best crossbreeding plan to use for rabbit meat
production in Nigeria. Kits used for this experiment belong to 3 parities and were weaned at 35 days of
age. Each rabbit was identified and weighed individually at weaning and at slaughter age (63 days). They
were slaughtered after 18 hours of fasting from feed only. After dissection the dressing percentage was
calculated as carcass weight x 100/live weight. Statistical analyses were performed using the General
Linear Model procedure of SAS. Crossbreeding parameters were calculated from linear contrasts between
breed group means. Results showed that breed differences exist for carcass weight in the purebreds,
where the CHC had significantly (P<0.05) higher carcass weight (1214g) than the NZW (1195g) and
CAW (1174). Pre-slaughter weight, carcass weight and dressing percentage were also affected by breed in
the purebreds and reciprocal crossbreds. Among the reciprocal crossbreds, NZW x CHC had highest
slaughter weight (1711g) while CHC x CAW had the highest carcass weight (1263g) and dressing
percentage (73.9%). Heart, liver, kidneys, lungs and other visceral organs showed no significant (P>0.05)
differences among the breed groups. Estimates of heterotic effect (%H’) calculated for carcass
characteristics in unit and percent (%) for slaughter weight in the CHC x NZW, NZW x CAW and CAW
x CHC crosses were 27.4 and 42%, 25.1 and 29% and 23.7 and 36%, respectively. Examined carcass
traits showed a general insignificant (P>0.05) heterosis. Maternal effects for various carcass traits also
showed no differences in all the crosses except for heart, kidneys and lungs (P<0.05). The maternal effect
herein is conceivably confounded with the reciprocal effect (ie sex linkage) since it is determined as the
difference between the three reciprocal crosses (NZW x CHC, CAW x NZW and CHC x CAW). The
results of this study show that the three selected populations do not seem to complement each other or
aggregate the responsible genes regarding heterotic and maternal effect as well as reproductive efficiency
of the studied carcass traits. Therefore, it can be assumed that the three breeds of rabbit could be used as
dam line for carcass traits.
Keywords: Breed, Carcass traits, Heterosis, Rabbits
INTRODUCTION
Rabbits raised for commercial rabbit meat production are usually produced by a three-way cross
involving crossbred dams mated to bucks from a sire line (Larzul and Rochambeau, 2004). The crossbred
dams are obtained from mating males and females from two dam lines selected for litter size (Kabir et al.,
2012) while the sire lines are generally selected for growth rate, affecting carcass and meat quality
(Baselga, 2003).
National Animal Production Research Institute
Ahmadu Bello University
P.M.B 1096, Shika-Zaria,
Kaduna State, Nigeria.
Email: japr@napri-ng.org Website: www.naprijapr.org
Kabir M.. et al
105
The New Zealand white (NZW) breed is known for its high breeding qualities which include prolificacy,
maternal performance, fast growth rate and precocious body development which make it ready for
slaughter at 56 days so as to obtain a light carcass (Kabir et al., 2014), while the Californian white (CAW)
breed is possibly the second most popular meat producing rabbit. The Chinchilla (CHC) rabbit falls under
both the medium and small class breeds. The Chinchilla Giganta, also called Grand Chinchilla, weighs
between 4.10 and 5kg, while the small Chinchilla weighs between 2.5 and 3.4kg (Piles et al., 2004).
Heterosis indicates the increase in fitness or productivity of crossbred offspring above the average of the
parental breeds because of increased heterozygousity (Ndjon and Nwakalor, 1999). Apart from heterosis,
reciprocal effect or deviations between the crosses of two or more breeds in which their roles as male or
female parents are reversed, represent another feasible route to the economic exploitation of interbreed
difference (Kabir et al., 2014; Pascual et al., 2004). The aim of this study was to estimate heterotic, direct
and maternal additive effects on carcass traits of three breeds of rabbit in Northern Guinea Savanna Zone
of Nigeria.
MATERIALS AND METHODS
Experimental site
The experiment was conducted at the Rabbitry Unit of the Research and Teaching Farm, Department of
Animal Science, Ahmadu Bello University Zaria, Nigeria. The site falls within the Northern Guinea
Savannah zone and detailed description of the location was given by Kabir et al. (2014).
Experimental animals and management
A total of 202, 272 and 256 records for purebred, crossbred and reciprocal-crossbred male and female
rabbits belonging to Chinchilla (CHC), Californian white (CAW) and New Zealand white (NZW) were
analyzed. All the experimental rabbits from which the records analyzed were derived were housed under
uniform conditions of management in hutches measuring 72cm x 62cm x 52cm. Experimental diets fed to
the animals and detailed mating plan was earlier reported (Kabir et al., 2014).
Slaughtering and carcass analysis
At the age of 63 days (±1day), rabbits were individually weighed and again 30 minutes before slaughter.
They were slaughtered within 24hours of fasting from feeds and dissected according to the method of
Larzul and Rochambeau, (2004). Carcass weight (g) was determined immediately after slaughter
excluding the blood, skin, tail, the gastro intestinal tract (GIT) and urogenital tract. Dressing percentage,
(the ratio between hot carcass weight and live weight of the rabbit expressed as percentage), weights of
heart, liver, kidney, lungs and other visceral organs were taken and expressed as percentage of carcass
weight.
Data analysis
Data obtained were subjected to Analysis of Variance using the General Linear Model (GLM) Procedure
of SAS (2002). For the analysis of carcass weight, the age at slaughter was taken as covariate. Maternal
heterosis and reciprocal effect was calculated using the method of Linear Contrasts (Dickerson, 1992) as
follows:
Heterosis and maternal effects for carcass traits
106
H′CHC {CHC x NZW} = {CHC x NZW + NZW x CHC} – {CHC x CHC + NZW x NZW}
H′NZW {NZW x CAW} = {NZW x CAW + CAW x NZW} – {NZW x NZW + CAW x CAW}
H′ CAW {CAW x CHC} = {CAW x CHC + CHC x CAW} – {CAW x CAW + CHC x CHC}
The percent heterosis was computed as follows:
While the reciprocal effect was calculated thus;
H′ = Estimate of maternal heterosis in unit and R′ is the estimate of reciprocal differences.
Heterosis was calculated using the general formula given below;
% heterosis = crossbred average – straightbred average
straightbred average
The statistical model used in this investigation was as follows: Yij = µ + Bi + Eij where Yij is the record
of jth kit of the ith breed group; Bi is the effect of ith breed group; µ is the random mean and Eij is the error
residual.
RESULTS
Carcass traits analysis
The carcass traits for the pure, main and reciprocal crosses are presented in Table 1. For the pure cross,
breed differences were observed for carcass weight, where the CHC had significantly (P<0.05) higher
carcass weight (1214g) than the NZW (1195g) and CAW (1174). Initial or pre-slaughter weight, carcass
weight and dressing percentage were also affected by breed in the main and reciprocal crosses. The mean
values obtained were 1734g, 1062g and 61.24% in the CHC x NZW cross; 1693g, 1139g and 67% in
NZW x CAW cross and 1616g, 1056g and 65.34% in the CAW x CHC cross, for pre-slaughter weight,
carcass weight and dressing percentage, respectively. The corresponding values obtained in the reciprocal
crosses were 1711g, 1188g and 69% in the NZW x CHC cross; 1655g, 1150g and 69% in the CAW x
NZW and 1709g, 1263g and 73% in the CHC x CAW cross. From the main-cross (Table 1), the CHC x
NZW gave significantly (P<0.05) higher slaughter weight (1734g) than NZW x CAW (1693g) and CAW
x CHC (1616g), while the NZW x CAW cross had higher carcass weight (1139g) and dressing percentage
(67%) than the CHC x NZW (1062g and 61.24%) and CAW x CHC (1056g and 65.34%). In the
reciprocal cross on the other hand, NZW x CHC was highest for slaughter weight (1711g) while CHC x
CAW had the highest carcass weight (1263g) and dressing percentage (73.9%). The heart, liver, kidneys,
lungs and other visceral organs showed no significant (P>0.05) differences among the breed groups.
H′ (unit)
mean of straightbred
x 100
R′ (unit)
mean of straightbred
x 100
x 100
Kabir M.. et al
107
Table 1: Least square means (±SE) for carcass traits
Traits
BREED GROUPa
Purebred
Crossbred
Reciprocal
CHC x
CHC
NZW x
NZW
CAW x
CAW
CHC x
NZW
NZW x
CAW
CAW x
CHC
NZW x
CHC
CAW x
NZW
CHC x
CAW
Live weight (g)
1696±47a
1674±40a
1638±41a
1734±63a
1693±48b
1616±52c
1711±88a
1655±20b
1709±53a
Carcass weight (g)
1214±42a
1195±66a
1174±53b
1062±34b
1139±71a
1056±18b
1188±50b
1150±38c
1263±49a
Dressing out percentage (%)
71.58a
71.38a
71.67a
61.24b
67.28a
65.34a
69.43b
69.48b
73.9a
Heart (%) (as % of carcass
weight)
0.44
0.41
0.46
0.47
0.35
0.51
0.44
0.53
0.49
Liver (%) “
5.10
5.12
5.96
5.93
4.66
5.25
5.70
4.93
5.11
Kidney (%) “
0.94
0.96
0.91
1.03
0.96
0.88
0.92
0.76
0.80
Lungs (%) “
1.25
1.21
1.15
1.22
1.07
1.13
1.26
1.05
1.19
Full gut (%) “
23.08
24.33
22.84
27.4
19.75
15.06
22.47
19.80
24.54
Empty gut (%) “
10.50
10.17
10.44
10.36
9.34
10.87
11.21
9.75
9.62
Head (%) “
13.95
13.88
13.23
13.93
14.61
13.74
14.31
14.85
13.96
Thigh (%) “
28.73
29.02
26.47
27.02
23.71
30.68
29.45
25.55
28.39
Skin (%) “
17.77
17.69
17.46
17.64
15.42
16.92
17.36
17.94
17.25
Length of small intestine (cm)
313a
295a
305a
316a
296a
278b
310a
264b
304a
Length of large intestine (cm)
184a
177b
181a
198a
184b
179b
190a
166c
170b
a CHC=chinchilla; NZW=New Zealand white; CAW=California white; N=Sample size
abc = Means in the same row (within the same cross) having the same letter are not significantly different
Heterosis and maternal effects for carcass traits
108
Heterosis and maternal effects for carcass traits
Estimates of heterotic effect (%H’) calculated for carcass characteristics are presented in Table 2. The estimates of heterosis in unit and percent
(%) for slaughter weight in the CHC x NZW, NZW x CAW and CAW x CHC crosses obtained were 27.4 and 42%, 25.1 and 29% and 23.7 and
36%, respectively. The examined carcass traits showed generally insignificant (P>0.05) heterosis. Maternal effects for various carcass traits
(Tables 2) showed no differences in all the crosses except for heart, kidneys and lungs (P<0.05). However, no particular trend was established for
the maternal effect on carcass traits studied.
Table 2: Heterosis and Maternal effects (±SE) for carcass traits
Traits
Direct heterosis
Maternal effect
CHC x NZW
NZW x CAW
CAW x CHC
Units
%
Units
%
Units
%
CHC x
NZW
NZW x
CAW
CAW x
CHC
Live weight (g)
27.4±34.7
42.1
25.1±11.4
29.42
23.73±30.0
36
-31.4±61.0
-28.3±45.4
-24.0±22.8
Carcass weight (g)
1.66±0.51
11.5
0.96±0.05
7.77
1.07±0.11
9.24
0.27±0.14
0.24±0.20
0.26±0.31
Dressing out percentage (%)
3.07±0.37
6.23
2.66±0.75
2.06
2.0±0.66
4.90
0.16±0.11
0.10±0.23
0.13±0.08
Heart (%) (as percentage of carcass
weight)
0.05±0.04
4.61
0.13±0.06
6.22
0.08±0.08
5.32
0.29±0.17*
0.21±0.21
0.18±0.16
Liver (%) “
0.08±0.02
2.19
0.05±0.02
2.27
0.16±0.32
1.94
-0.21±0.22
-0.18±0.20
-0.13±0.17
Kidney (%) “
0.02±0.03
3.33
0.04±0.01
3.72
0.67±0.25
2.69
0.16±0.13*
0.12±0.23
0.93±0.21
Lungs (%) “
0.05±0.04
3.06
0.05±0.06
4.02
0.08±0.05
3.62
0.32±0.14*
0.27±0.24
0.23±0.23
Full gut (%) “
-0.63±0.56
-6.29
-0.54±0.43
-4.36
0.11±0.26
2.54
-0.18±0.13
-0.15±0.21
0.10±0.17
Empty gut (%) “
-0.49±0.32
-5.45
-0.35±0.28
-2.99
-0.28±0.15
-0.30
-0.08±0.06
-0.11±0.15
0.07±0.09
Head (%) “
0.58±0.24*
18.36
0.39±0.41
16.18
0.41±0.41
0.32
0.25±0.51
0.21±0.30
0.30±0.23
Kabir M.. et al
109
Thigh (%) “
-0.01±0.21
-2.90
-0.03±0.33
-3.14
-0.06±0.21
-3.02
-0.11±0.34
-0.32±0.26
-0.28±0.18
Skin (%) “
-0.44±0.17
-8.98
-0.27±0.17
-6.22
-0.36±0.23
-7.14
-0.07±0.22
-0.13±0.17
-0.09±0.14
Length of small intestine (cm)
6.44±3.02
16.66
3.78±3.11
19.65
3.11±3.26
18.19
11.42±6.02
7.39±4.55
5.29±4.32
Length of large intestine (cm)
3.39±3.18
21.30
4.46±3.24
19.82
3.67±3.18
17.25
8.33±6.17
6.54±4.11
5.63±3.62
CHC=Chinchilla; NZW=New Zealand white; CAW=California white
* = P<0.05
Heterosis and maternal effects for carcass traits
110
DISCUSSION
Carcass traits
Variation among rabbit breeds and crossbreeding combinations of different origin for carcass
traits exist (Szendro et al., 1994; Ouyed and Brun 2008; Bawa et al., 2009). The variation
observed in this study with respect to main-cross for slaughter weight, carcass weight and
dressing percentage is in line with the reports of Oke et al., (2010) where they observed higher
mean values for live weight, carcass weight and dressing percentage in the CHC x NZW
crossbreds. Das and Bujarbarua, (2005) had earlier noted a higher live weight of these breeds
compared to the Dutch breed. The relatively low and non-significant differences observed for
heart, liver, kidneys, lungs and other visceral organs in the pure, main and reciprocal crosses
could be explained by the environmental circumstances, which could influence the ability of the
breeds. However, values of carcass traits are difficult to be compared objectively with those
reported in literature because of the different initial or pre-slaughter weights, breeds, method of
slaughter and evaluations as well as the statistical model adopted (Kabir et al., 2012).
Heterosis and maternal effects for carcass traits
Results obtained in this study for heterotic effects on carcass traits agree with those of Oke et
al., (2010) who reported that the proportions of carcass traits differed slightly between the
purebreds and crossbreds. According to Ahmed (2003), crossing does not only take advantage
of traits with considerable non-additive genetic variations (dominance and epistasis), but also
exploits differences in additive effects (differences in mean performance between populations as
a deviation from the overall mean) between populations. Maternal effect consists mainly from
additive maternal and cytoplasmic-inheritance. However, the maternal effect herein is
conceivably confounded with the reciprocal effect (sex linkage) since it is determined as the
difference between the three reciprocal crosses (NZW x CHC, CAW x NZW and CHC x
CAW). Sex linkage as an effect is due to additive effects of genes concerned with the trait and is
carried on the sex chromosomes (Ahmed, 2003).
CONCLUSION
In explaining maternal effect in terms of complementarity effects, certain crosses may show
much more maternal effect than others depending on the extent to which the crossed
populations differ in reproductive performance and in production characters. Therefore, this
type of effect, according to Kabir et al., (2014) will rely on the direction of crossing, hence the
negative signs obtained for some carcass traits in this study (Table 2).
The results of this study show that the three selected populations do not seem to complement
each other or aggregate the responsible genes regarding heterotic and maternal effect as well as
reproductive efficiency of the studied carcass traits. Therefore, it can be assumed that the three
breeds of rabbit could be used as dam line for carcass traits.
Kabir M.. et al
111
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