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African Journal of Pig Farming ISSN 2375-0731 Vol. 5 (4), pp. 001-006, April, 2017. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

Full Length Research Paper 

 

Polymorphism and association of microsatellite SJ01 
with birth weight and early growth traits in pigs 

 
Y. J. Zhang1,2, G. C. Li1 and Y. L. Jiang1* 

 
1
Laboratory of Animal Molecular Genetics, College of Animal Science and Veterinary Medicine, Shandong Agricultural 

University, Taian 271018, China. 
2
College of Life Science, Linyi Normal University, Linyi 276005, China. 

 
Accepted 22 November, 2016 

 
Myostatin is a negative regulator of animal skeletal muscle development and SJ01 is a microsatellite locus 
flanking porcine myostatin gene. In the present study, the polymorphism of microsatellite SJ01 in three pig 
populations, that is, Duroc (n = 420), Yorkshire (n = 414) and Landrace (n = 119), were investigated, and its 
associations with birth weight and early growth traits were analyzed. The results indicated that genotype BB 
was predominant in Yorkshire pigs and allele B was predominant in both Yorkshire and Landrace pigs, whereas 
allele A was more prevalent in Duroc pigs. Among the three pig breeds, Duroc population had the highest 
heterozygosity and deviated from Hardy-Weinberg equilibrium (P < 0.05). The average daily gain from 28 d to 70 
d in Yorkshire pigs and the body weight at 70 d in Landrace pigs were significantly different between SJ01 
genotypes (P < 0.05). These results suggest that microsatellite SJ01 is a potential DNA marker for early growth 
trait selection in Yorkshire and Landrace pigs as well as for refining QTL for early growth traits on SSC15. 

 
Key words: Pig, myostatin, microsatellite SJ01, polymorphism, early growth traits. 

 
INTRODUCTION 

 
Myostatin is a negative regulator of skeletal muscle mass 
in mammals (McPherron et al., 1997). Natural mutations, 
such as deletions, point mutations in myostatin coding re-
gion, intronic region or 3′-untranslated region, bring about 
double-muscling traits in beef cattle (McPherron and Lee, 
1997), sheep (Clop et al., 2006; Boman et al., 2009), 
human (Schuelke et al., 2004) and dogs (Mosher et al., 
2007). In pigs differing in muscular traits, such as wild 
boar, Pietrain and Laiwu pigs, however, no mutation with 
similar effect in myostatin gene was reported (Jiang et al., 
2002a; Stinckens et al., 2008). Recent studies reported 
associations of polymorphisms in the promoter region of 
porcine myostatin gene with production traits (Jiang et al., 
2002b), meat quality traits (Guimaraes et al., 2007) and 
mRNA level (Stinckens et al., 2008), suggesting that, in 
pigs, myostatin might also play important roles in the 
development of skeletal muscle and its related traits.  

Microsatellite loci are frequently used as DNA markers 
to locate quantitative trait loci (QTL), but usually to a  
 
 
 
*Corresponding author. E-mail: yunliangjiang@gmail.com. 

 
 
 

 
relatively wide range of chromosomal fragment, in which 

many genes reside. To find the functional gene(s) or 
quantitative trait nucleotide (QTN) fine mapping with more 
markers is required. Microsatellite SJ01, which was iden-
tified by our previous study, is a locus located 42 kb 
downstream of porcine myostatin gene (Jiang et al., 
2004) whether it is associated with production traits and 
can be used as DNA marker remain unknown.  

Birth weight and early growth traits were two econo-
mically important traits in that, on one hand, they directly 
affect the mortality rate of weanling pigs and on another 
hand, are associated with growth rate and carcass traits 
on test. A QTL mapping study based on a F2 pedigree 
constructed with wild boar ×Yorkshire suggested one QTL 
for average daily gain from birth to 70 d on SSC15 (50 
cM, male; 78 cM, female) (Knott et al., 1998), the map-
ping interval was partially overlapped with myostatin gene 
and SJ01 locus.  

The production traits associated polymorphisms involve 
three sites in the promoter region of porcine myostatin 
gene (Jiang et al., 2002a; Guimaraes et al., 2007; Yu et 
al., 2007; Stinckens et al., 2008), the detection of which is 
not practical for use in molecular pig breeding. Therefore, 



  
 
 

 
Table 1. Means and s.d. of birth weight and early growth traits. 

 

Trait 
 Breed  

 

Duroc Yorkshire Landrace 
 

 
 

BW0 (kg) 1.44 ± 0.31 1.49 ± 0.31 1.46 ± 0.25 
 

BW28 (kg) 7.12 ± 1.52 7.53 ± 2.05 8.53 ± 2.15 
 

BW70 (kg) 21.13 ± 5.27 21.78 ± 5.53 24.77 ± 5.65 
 

ADG1 (kg) 0.20 ± 0.05 0.20 ± 0.06 0.25 ± 0.08 
 

ADG2 (kg) 0.36 ± 0.10 0.50 ± 0.13 0.35 ± 0.07 
 

 
BW0, BW28 and BW70 represent birth weight, body weight at 28 d and body weight 
at 70 d, respectively.  
ADG1 and ADG2 represent average daily gain from birth to 28 d and from 28 to 70 
d, respectively. 

 

 

It is necessary to find another closely linked marker. 
Given the important role of myostatin in meat traits and 
the short physical distance between myostatin and SJ01, 
we speculate that SJ01 is likely associated with some 
production traits in pigs and therefore is a candidate 
marker. In this study, the polymorphism at SJ01 locus 
and its associations with porcine body weight and early 
growth traits were analyzed in three pig breeds (Duroc, 
Yorkshire and Landrace) which are currently used for 
worldwide pork production. 
 

 
MATERIALS AND METHODS 
 
Population and traits 

 
Three western pig breeds, including 420 Duroc, 414 Yorkshire and 
119 Landrace individuals were randomly sampled from Pig Breed-
ing Center of Shandong Academy of Agricultural Sciences. Animals 
were reared under the same environment and had free access to 
feed and water. Data of the traits including birth weight (BW0), body 
weight on day 28 (BW28) and body weight on day 70 (BW70) of 
each individual were collected on farm. Sampling was performed by 
taking a notch from the ear of pigs and put into a 1.5-mL Eppendorf 
tube containing 70% ethanol and stored at −20ºC. The total number 
of production records was 2757 and the mean and standard 
deviation (s.d.) of the five traits are presented in Table 1. 

 

Isolation of genomic DNA 

 
Genomic DNA from ear notch was isolated with phenol/chloroform 
method (Sambrook and Russell, 2001), dissolved in Tris-EDTA buf-
fer (pH 8.0) and stored at −20ºC. The concentration was checked 
by running 0.7% agrose electrophoresis and using UV spectro-
photometer. 
 

 
Genotyping 

 
Primers for SJ01 were from STS database of National Centre for 
Biological Information (UniSTS accession number: 81993): Forward 
5′-CAGAACATAAATGCCAAGAG-3′ and Reverse 5′-AGTATTTA 
GTGAACACCTCG-3′. PCR was performed by mixing 0.3 µL (50 - 
100 ng) of genomic DNA, 1.6 µL of dNTPs (2.5 mM each), 1.2 µL of 

MgCl2 (25 mM), 0.5 µL each of primers (10 µM), 0.1 µL of rTaq 
polymerase (5 U/µL, TaKaRa, Dalian China) and 2.0 µL of 1×rTaq 

 
 

 
buffer in a 20 µL volume and running on a Mastercycler gradient 
(Eppendorf, Germany) according to the following program: 95ºC for 
3 min, 32 cycles of 95ºC for 30 s, 55ºC for 30 s and 72ºC for 30 s 
and final extension at 72ºC for 5 min. The PCR products were 
electrophoresed on 1.5% agarose gel to check amplification 
efficiency.  

Genotyping of SJ01 was carried out by running 12% polyacryl-

amide gels (arc：bis = 19:1) with 1×TBE as electrophoresis buffer 
 
at 180 V for 10 h. After electrophoresis, the gels were silver-stained 
and the genotype was determined according to the electrophoresis 
band patterns. 

 

Sequencing 

 
The PCR products were purified with Gel Extraction System B 
(BioDev, China), inserted into pMD-18T vector and was used to 
transform E. coli DH5 α competent cells. At least four clones were 
sequenced using the BigDye v3.1 kit (Applied Biosystem) by 
Shanghai Songon Co. Ltd (Shanghai, China). 

 

Statistics 

 
The genotype frequency, allele frequency, observed heterozygosity 
(Ho), expected heterozygosity (He), average heterozygosity (Ha), 
number of available alleles (na), number of effective alleles (ne) and 
polymorphic information content (PIC) were obtained and the 
deviation from Hardy-Weinberg equlibrium was tested with Popgen 
32 software.  

Associations of SJ01 genotypes with BW0, BW28, BW70, 
average daily gain from birth to day 28 (ADG1) and average daily 
gain from day 28 to day 70 (ADG2) were performed separately in 
Duroc,Yorkshire and Lanrace pigs with the PROC GLM procedure 
of SAS 8.2 software (SAS Institute Inc, 1998). In the statistics 
model, genotype, farm-year-season and sex were treated as fixed 
effects, litter size as co-variable to eliminate the influences of litter 
size on birth weight (Model 1), birth weight as co-variable to 
eliminate the influences of birth weight on body weight (Model 2) 
and start body weight as co-variable to eliminate the influences of 
start body weight on average daily gain (Model 3). 
 

Model 1: Yijklm=µ+Di+Cj+Sk+Zl+eijklm; 
 

Model 2: Yijklm=µ+Di+Cj+Sk+Bl+eijklm; 
 

Model 3: Yijklm=µ+Di+Cj+Sk+Pl+eijkml; 
 

where Yijklm is the birth weight (BW0), body weight (BW28, BW70) 



  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Figure 1. Genotyping and identification by sequencing of microsatellite SJ01 locus. a. PCR amplification; b. 
genotyping. Lanes 1-11 represent genotypes AA, BD, AB, AC, BC, BE, DD, DD, CD, BB, AD and CC, 
respectively. c. Sequencing result, indicating dinucleotide (TG) repeats of 16, 17 and 22, respectively.  

 

 
and average daily gain (ADG1, ADG2) of each individual for models 
1-3 respectively; µ is the overall mean of population; Di is the mean 
effect of genotype i; Cj is the farm-year-season effect; Sk is the 
effect of sex; Zl is the effect of litter size (Model 1); Bl is the effect of 
birth weight (Model 2); Pl is the effect of start body weight (Model 
3); eijklm is the residual effect.  

The difference between genotypes was considered as significant 
when P < 0.05. 

 
 

 

AC, BC, BE, DD, CD, BB, AD and CC is shown in Figure 
1b. Among the five alleles, alleles A and B were reported 
by our previous study, which were composed of 13 and 
19 repeats of dinucleotide (TG), respectively (Jiang et al., 
2004); alleles C, D and E were composed of 16, 17 and 
22 repeats of dinucleotide (TG), respectively (Figure 1c) 
and were reported for the first time by present study. 
 

 

RESULTS 

 

Genotypes and alleles 

 
Analysis of SJ01 polymorphism revealed 13 genotypes 
(AA, AB, BB, BC, BD, BE, AC, AD, AE, CC, CD, DD and  
EE) and five alleles (A, B, C, D and E) in Duroc (n = 420), 
Yorkshire (n = 414) and Landrace (n = 119) pig popula-
tions. The electriphoresis result of genotypes AA, BD, AB, 

 
 
Population genetic parameters at SJ01 locus 

 

Differences in genotype frequency and allele frequency 
were found between three pig populations of Duroc, 
Yorkshire and Landrace (Table 2). For genotypes with 
frequency exceeding 0.1, genotypes AB, AA and AD in 
Duroc, AB, BB and BE in Yorkshire and BB and BD in 
Landrace were identified. Genotypes BC, AE, CC, CD 
and EE occurred at low frequencies in all of the three pig 



  
 
 

 
Table 2. Genotype frequency of microsatellite SJ01 in Duroc, Yorkshire and Landrace populations. 
 

Breed (n) AA AB BB BC BD BE AC AD AE CC CD DD EE 

Duroc (420) 0.2167(91) 0.2905(122) 0.0762(32) 0.0048(2) 0.081(34) 0.0024(1) 0.0357(15) 0.2500(105) 0.0000(0) 0.0024(1) 0.0143(6) 0.0262(11) 0.0000(0) 

Yorkshire(414) 0.0024 (1) 0.1232(51) 0.6594(273) 0.0000(0) 0.0773(32) 0.1232(51) 0.0000 (0) 0.0024 (1) 0.0048(2) 0.0000(0) 0.0000(0) 0.0024 (1) 0.0048(2) 

Landrace(119) 0.0000 (0) 0.0000(0) 0.5210(620) 0.0000(0) 0.4034(48) 0.0084 (1) 0.0000 (0) 0.0000 (0) 0.0000(0) 0.0000(0) 0.0000(0) 0.0672 (8) 0.0000(0) 
 

 
Table 3. Allele frequency and population genetic parameters of microsatellite SJ01 in Duroc, Yorkshire and Landrace populations. 

 

Breed A B C D E H-W test Ho He Ha na ne PIC 

Duroc 0.5048 0.2655 0.0298 0.1988 0.0012 0.0252 0.6786 0.6351 0.6343 5.0000 2.7347 1.1309 

Yorkshire 0.0676 0.8213 - 0.0423 0.0688 0.4226 0.3309 0.3148 0.3144 4.0000 1.4587 0.6618 

Landrace - 0.7269 - 0.2689 0.0042 0.9308 0.4118 0.4010 0.3993 3.0000 1.6647 0.6080 
 

 
Table 4. Least squares means for performances among genotypes of microsatellite SJ01 in Duroc populations. 

 

Performance AA AB AC AD BD P-value 

BW0 1.41 ± 0.03 (n = 88) 1.47 ± 0.03 (n = 112) 1.41 ± 0.09 (n=13) 1.47 ± 0.03 (n = 101) 1.49 ± 0.05 (n = 34) 0.7686 

BW28 7.18 ± 0.17 (n = 67) 7.28 ± 0.16 (n = 72) 7.12 ± 0.50 (n=8) 7.10 ± 0.18 (n = 57) 7.06 ± 0.26 (n = 27) 0.8664 

BW70 21.31 ± 0.72 (n = 57) 21.51 ± 0.64 (n = 71) 19.39 ± 2.01 (n=7) 20.00 ± 0.73 (n = 56) 20.76 ± 1.13 (n = 22) 0.3297 

ADG1 0.20 ± 0.01 (n = 65) 0.21 ± 0.01 (n = 66) 0.20 ± 0.02 (n=7) 0.20 ± 0.01 (n = 55) 0.20 ± 0.01 (n = 27) 0.8664 

ADG2 0.36 ± 0.01 (n = 43) 0.36 ± 0.01 (n = 43) 0.36 ± 0.07 (n=2) 0.35 ± 0.02 (n = 29) 0.36 ± 0.02 (n = 17) 0.9808 
 

BW0, BW28 and BW70 represent birth weight, body weight at 28 d and body weight at 70 d, respectively. 
ADG1 and ADG2 represent average daily gain from birth to 28 d and from 28 to 70 d, respectively. 

 

 

populations. In Yorkshire pigs, genotype BB was 
predominant, while in Duroc and Landrace pigs, 
no predominant genotype was found. As for allele 
frequencies, five, four and three alleles were 
detected in Duroc, Yorkshire and Landrace pig 
populations, respectively and allele B was predo-
minant in Yorkshire and Landrace, whereas allele 
A was more prevalent in Duroc populations (Table 
3). At SJ01 locus, Yorkshire and Landrace, but not 
Duroc, were in a state of Hardy-Weinberg equili-
brium (P > 0.05). Information obtained from other 
genetic parameters of Ho, He and PIC (Table 3) 

 
 

 

indicated that, at this locus, Duroc is genetically 
more diverse compared to Yorkshire and Land-
race pig populations. 
 

 

Associations of SJ01 genotype with birth 
weight and early growth traits 

 

The relationship of SJ01 genotype with birth 
weight and some early growth traits, that is, body 
weight at 28 d and 70 d and average daily gain 
from birth to 28 d and from 28 to 70 d, were analy- 

 
 

 

zed in present study. The results showed that, in 
Duroc pig populations, differences in birth weight, 
body weight at 28 and 70 d and average daily gain 
traits were not significant between genotypes of 
SJ01 locus (P > 0.1) (Table 4); whereas in York-
shire pig populations, the least squares means for 
average daily gain from 28 to 70 d were signifi-
cantly different among genotypes of SJ01 locus (P  
< 0.05) (Table 5) and in Landrace pigs, the least 
squares means for body weight at 70 d were 
significantly different among genotypes of SJ01 
locus (P < 0.05) (Table 6). The effect of SJ01 on 



 
 
 

 
Table 5. Least squares means for performances among genotypes of microsatellite SJ01 in Yorkshire populations. 

 

Performance AB  BB    BD   BE  P-value 

BW0 1.44 ± 0.06 (n =51) 1.48 ± 0.02 (n = 272)  1.57±0.07 (n = 32)  1.56±0.05 (n = 51)  0.2361 

BW28 7.54 ± 0.34 (n =34) 7.63 ± 0.17 (n = 161)  7.01±0.49 (n = 16)  6.80±0.37 (n = 29)  0.1581 

BW70 20.45 ± 1.01 (n = 28) 22.05 ± 0.40 (n = 176)  22.48±1.21 (n = 19)  19.87±0.84 (n = 40)  0.0631 

ADG1 0.21 ± 0.01 (n = 30) 0.21 ± 0.00 (n = 149)  0.17±0.02 (n = 12)  0.19±0.01 (n = 28)  0.0910 

ADG2 0.42 ± 0.03 (n = 18) 0.49 ± 0.01 (n = 104)  0.53±0.04 (n = 9)  0.47±0.02 (n = 23)  0.0464 

BW0, BW28 and BW70 represent birth weight, body weight at 28 d and body weight at 70 d, respectively.      
ADG1 and ADG2 represent average daily gain from birth to 28 d and from 28 to 70 d, respectively.      

Table  6.  Least squares means for performances among genotypes of microsatellite SJ01  in Landrace  
populations.               

              

 Performance   BB  BD   DD   P-value  

 BW0  1.46 ± 0.03 (n = 61)  1.44 ± 0.04 (n = 48)  1.47 ± 0.10 (n = 8)  0.8384   

 BW28  8.35 ± 0.25 (n = 49)  8.51 ± 0.36 (n = 25)  7.14 ± 1.22 (n = 2)  0.5400   

 BW70  24.53 ± 0.83 (n = 27)  26.60 ±1.33 (n = 9)  33.02 ± 2.83 (n = 2)  0.0268   

 ADG1  0.25 ± 0.01 (n = 48)  0.25 ± 0.01 (n = 25)  0.20 ± 0.04 (n = 2)  0.5400   

 ADG2  0.38 ± 0.03 (n = 20)  0.35 ± 0.04 (n = 3)  -    0.6554   
 

BW0, BW28 and BW70 represent birth weight, body weight at 28 d and body weight at 70 d, respectively.  
ADG1 and ADG2 represent average daily gain from birth to 28 d and from 28 to 70 d, respectively. 

 

 

other production traits of Yorkshire and Landrace pigs 
was not significantly different (P > 0.5). 

 

DISCUSSION 
 

Myostatin is an important growth/differentiation factor 
regulating skeletal muscle development, therefore, is also 
associated with meat production and quality traits as well 
as with other related traits. Porcine myostatin gene is 
mapped in a SW1065-(53.1)-SW1263- (55.0)-myostatin-
(55.0)-SWR1533 -(57.9) linkage group on SSC15q2.3 
(Sonstegard et al., 1998), the flanking microsatellite loci 
SW1263 and SWR1553 were located at 55.0 and 57.9 
cM, respectively. The microsatellite locus SJ01 is located 
42 kb downstream of myostatin gene, more close to myo-
statin gene than SWR1553. Compared with other 
microsatellite loci located in nonstructural gene region, 
the number of genotypes and alleles were rather few 
(Jiang et al., 2004 and present study) and the hetero-
zygosity and diversity were rather low for SJ01, sug-
gesting relatively higher selection force and more conser-
vation in this region than microsatellite loci located in 
nonstructural gene regions. According to the results of 
SJ01 polymorphism, of the three pig breeds used in this 
study, Duroc pigs were more diverse and its genetic 
component was more complex.  

A QTL for average daily gain from birth to 70 d was 
mapped on SSC15 (50 cM, male; 78 cM, female) (Knott 
et al., 1998), where myostatin gene and SJ01 locus also 
reside. In this study, SJ01 locus is found to be associated 
with average daily gain from 28 to 70 d in Yorkshire pigs 

 
 

 

and with body weight at 70 d in Landrace pigs. Besides, a 
nearly significant association was also noted for SJ01 
with body weight at 70 d and average daily gain from birth 
to 28 d in Yorkshire pigs. These data suggest that this 
region likely harbors a QTL affecting early growth and 
SJ01 is a useful marker for refining this QTL.  

Growth traits, such as body weight and average daily gain, 

are controlled by multiple genes. In addition to the 

aforementioned QTL for average daily gain from birth to 70 d 

on SSC15 (Knott et al., 1998), other QTLs for body weight of 

10 weeks were found on SSC1, 4, 6, 7 and 9 and for 

average daily gain from 4 weeks to 13 weeks on SSC9 and 

SSC10, from 3 weeks to 10 weeks on SSC 1, 2, 4 and 7, 

respectively (http://www. animalgenome.org/ QTLdb 

/pig.html). The effect of each gene or QTL on early growth 

traits is somewhat dependent on genetic background and 

environmental effect, giving rise to the differences between 

breeds concerning the relationship of SJ01 genotype with 

these traits, as shown in this study.  
Although three relatively large populations of Duroc, 

Yorkshire and Landrace were used for association study, 
some genotypes were present at low frequency, that is, 
genotype DD in Landrace population. The effect of SJ01 
genotype on birth weight at 70 d in Landrace pigs re-
quires further research with a large population containing 
more individuals with genotype DD, or in some pedigrees 
segregating at this locus.  

In conclusion, SJ01 is a potential DNA marker for 
average daily gain from 28 to 70 d in Yorkshire and for 
body weight at 70 d in Landrace pigs and is useful for 
refining QTL position for early growth traits. 



 
 
 

 

ACKNOWLEDGEMENTS 

 

This work was supported by the 863 high-technology 
project of China (No. 2006AA10Z1E1). We thank S. Liang 
for helpful discussion. 
 

 
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