Article Type : Research Article
Authors : Shaidullin RR, Zagidullin LR, Akhmetov TM, Moskvicheva AB, Tyulkin SV, Faizov TKH and Mohammed L
Keywords : Genotype; CSN3; DGAT1; GH; PRL; Allele; Proportion of the influence; ?2; indicators of milk production
The purpose of the work was to study the power
and reliability of the influence of the genotypes of kappa-casein (CSN3),
diacylglycerol O-acyltransferase (DGAT1), somatotropin (GH), prolactin (PRL) on
the indicators of milk production of black-and-white cattle. It was revealed
that the CSN3 genotype had the greatest significant influence on the mass
fraction of protein in milk, the proportion of its influence was ?2 = 0.353
(Ffactual= 40.323; P<0.001) in first-calf heifers and it was ?2= 0.140
(Ffactual= 13.400; P<0.001) in full-aged cows. There was also found an
influence on milk protein yield that was ?2= 0.074 (Ffactual= 5.882; P<0.01)
and ?2= 0.039 (Ffactual= 3.390; P<0.05). The DGAT1 genotype had a highly
significant effect (P<0.001) on the fat mass fraction in milk for the 1st
lactation ?2= 0.189 (Ffactual= 17.202), for the 3rd lactation ?2= 0.109
(Ffactual= 10.101). According to the somatotropin gene, a significant degree of
influence of the genotype was revealed in full-aged cows only by milk yield per
lactation ?2= 0.057 (Ffactual= 4.949; P<0.01), and by the prolactin gene in
terms of fat content of milk ?2= 0.044 (Ffactual= 3.822; P<0.05). The
desired allele B of the CSN3 gene has a significant effect only on the mass
fraction of protein ?2= 0.342 with the maximum value of the Fisher criterion that
is Ffactual= 26.489 (P<0.001), and the allele K of the DGAT1 gene on the
mass fraction of fat in milk ?2= 0.163 (Ffactual= 17.305; P<0,001) and the V
allele of the somatotropin gene on milk protein yield ?2= 0,097 (Ffactual=
3.641; P<0.05). The genotypes CSN3 and DGAT1 have the widest influence on
the indicators of milk production of cows.
Effective selection work in dairy cattle
breeding is possible only with the integrated use of zoo technical methods and
modern DNA technologies. The use of molecular genetic methods for early
prediction of the magnitude and direction of the productive qualities of an
individual increases the rate of breeding progress by half and contributes to
obtaining a significant economic effect [1]. The use of genetic markers in
cattle breeding responsible for milk production will improve the economically
useful characteristics of cows. Alleles of genes of milk proteins; hormones and
enzymes are considered as potential DNA markers of milk production and milk
quality in cattle. Some of these markers are genes for kappa-casein and
diacylglycerol O-acyltransferase; somatotropin; prolactin [2-3]. Nowadays a
special attention is paid to the gene locus of one of the main milk proteins
that is kappa-casein. It is known that allelic variants of the milk protein of
kappa-casein are connected with indicators of protein content of milk; and the
yield of milk protein by the technological properties of milk [4-7].
Diacylglycerol O-acyltransferase (DGAT1) gene involved in fatty acids
metabolism. DGAT1 gene of cattle is mapped to the centromeric side of
chromosome 14. Studies of Russian and foreign authors have revealed that this
mutation significantly affects the milk production of cows; in particular; the
milk yield and fat content of milk. At the same time it has been established
that allele A is associated with high milk production and allele K is
associated with a high content of mass fraction of fat in milk [8-11]. The use
of hormone genes - prolactin (PRL) and somatotropin (GH) as DNA markers of milk
production in cattle is connected with the participation of proteins encoded by
them in the regulation of lactation; synthesis and secretion of various
constituents of milk [12-13]. Thus; cows with the BB genotype for the prolactin
gene have a higher fat content of milk and; accordingly; have a higher yield of
milk fat and protein [14-15]. The influence of various allelic variants of the
GH gene on the indicators of milk production of cows (milk yield; fat and
protein content of milk) was also determined [16-18]. The issue of improving
the productive qualities of cows is a daily problem and is based on a
combination of genetic and non-genetic factors. As a consequence; an important
problem arises of studying the proportion of the influence of different
genotypes of DNA markers on the productive qualities of dairy cattle. In this
regard; the purpose of the work is to study the power and reliability of the
influence of the genotypes of kappa-casein; diacylglycerol O-acyltransferase;
somatotropin and prolactin on the indicators of milk production of
black-and-white cattle.
In order to conduct the research and genotyping
for kappa-casein; diacetylglycerol O-acetyltransferase; somatotropin; prolactin
151 first-calf heifers and 168 full-aged black-and-white cows; from which blood
samples were taken and DNA samples were isolated; were selected in the
conditions of the breeding reproducer of OOO «Dusym» (Dusym; LLC) of Atninsky
District in the Republic of Tatarstan. The material for molecular DNA testing
was the venous blood of animals. DNA isolation was carried out using the
Magnosorb kit (Interlabservice; Moscow); according to the manufacturer's
instruction. Genotypes CSN3; DGAT1; GH; PRL were determined by PCR-RFLP
(restriction fragment length polymorphism). Amplification was carried out on a
Tertsik amplifier (DNA-technology; Moscow). Depending on presence of alleles A
and B of the CSN3 gene; genotypes were divided into three groups (AA; AB; BB);
alleles A and K of the DGAT1 gene; genotypes were divided into three groups
(AA; AK; KK); alleles V and L of the GH gene; genotypes were divided into three
groups (VV; VL; LL); alleles A and B of the PRL gene; genotypes were divided
into three groups (AA; AB; BB). Data on milk production for 1st and 3rd
lactation of cows with different genotypes CSN3; DGAT1; GH; PRL were used for
the study. One-way analysis of variance was carried out using the Excel
software application from the Microsoft Office package; according to which the
influence of the polymorphism factor of the studied genes on the indicators of
milk production of cows was determined.
Studies have shown that the kappa-casein genotype
had the greatest significant effect on the protein mass fraction in cow's milk;
its proportion of influence in first-calf heifers was ?2= 0.353 (F= 40.323;
P<0.001); in full-age cows was ?2= 0.140 (F= 13.400; P<0.001) (Table 1).
Table
1: The
proportion and significance of the influence of the kappa-casein genotype on
the indicators of milk production of cows.
? |
Indicator |
1st
lactation |
3rd
lactation | ||||
?2, % |
Ffactual |
? |
?2, % |
Ffactual |
? | ||
1 |
Milk yield per
lactation |
0.013 |
0.993 |
0.373 |
0.020 |
1.661 |
0.193 |
2 |
Mass fraction
of fat |
0.030 |
2.294 |
0.104 |
0.015 |
1.285 |
0.280 |
3 |
Milk fat |
0.019 |
1.456 |
0.236 |
0.025 |
2.086 |
0.127 |
4 |
Mass fraction
of protein |
0.353 |
40.323*** |
0.0001 |
0.140 |
13.400*** |
0.0001 |
5 |
Milk protein |
0.074 |
5.882** |
0.003 |
0.039 |
3.390* |
0.036 |
Hereinafter:
* - P<0.05, ** - P<0.01, *** - P<0.001 |
Also; a significant influence of the kappa-casein
genotype was revealed on the yield of milk protein in the 1st lactation that
was ?2= 0.074 (F= 5.882; P<0.01) and ?2= 0.039 (F= 3.390; P<0.05). The
influence of the kappa-casein gene did not exceed 0.030 and was not reliable in
terms of other indicators of milk production. Consequently; a high power of the
influence of the kappa-casein gene on protein content of milk of cows was
revealed. A high and reliable effect was revealed in terms of the mass fraction
of fat in milk in cows for the diacylglycerol O-acyltransferase gene for the
1st lactation that was ?2= 0.189 (F= 17.202; P<0.001); that was ?2= 0.109
(F= 10.101; P<0.001) for the 3rd lactation (table 2). And a significant
influence was also found on the amount of milk fat in first-calf heifers ?2=
0.059 (F= 4.656; P<0.01).
Consequently; a high power of influence of the
diacylglycerol O-acyltransferase gene on the fat content of milk of cows was
revealed. It should be mentioned that although the indicator of the milk yield
per lactation was unreliable; it had a rather good value of the proportion of
influence ?2 = 0.032 and 0.026. It can signify about some influence of the gene
of diacylglycerol O-acyltransferase on the level of milk yield in cows too. According
to the somatotropin gene in experimental animals; a significant degree of
genotype influence was revealed only by milk yield for the 3rd lactation ?2=
0.057 (F= 4.949; P<0.01) (table 3). ?2 was less than 0.028 and unreliable in
terms of other indicators of milk production (Table 2).
Table
2: The
proportion and significance of the influence of the genotype of diacylglycerol
O-acyltransferase on the indicators of milk production of cows.
? |
Indicator |
1st
lactation |
3rd
lactation | ||||
?2, % |
Ffactual |
? |
?2, % |
Ffactual |
? | ||
1 |
Milk yield per
lactation |
0.032 |
2.437 |
0.091 |
0.026 |
2.219 |
0.112 |
2 |
Mass fraction
of fat |
0.189 |
17.202*** |
0.0001 |
0.109 |
10.111*** |
0.0001 |
3 |
Milk fat |
0.059 |
4.656** |
0.011 |
0.005 |
0.383 |
0.682 |
4 |
Mass fraction
of protein |
0.003 |
0.203 |
0.817 |
0.012 |
1.033 |
0.358 |
5 |
Milk protein |
0.026 |
1.991 |
0.140 |
0.005 |
0.455 |
0.635 |
Table
3: The
proportion and reliability of the influence of the somatotropin genotype on the
indicators of milk production of cows.
? |
Indicator |
1st
lactation |
3rd
lactation | ||||
?2, % |
Ffactual |
? |
?2, % |
Ffactual |
? | ||
1 |
Milk yield per
lactation |
0.025 |
1.895 |
0.154 |
0.057 |
4.949** |
0.008 |
2 |
Mass fraction
of fat |
0.028 |
2.095 |
0.127 |
0.004 |
0.340 |
0.712 |
3 |
Milk fat |
0.021 |
1.566 |
0.212 |
0.001 |
0.114 |
0.892 |
4 |
Mass fraction
of protein |
0.005 |
0.338 |
0.714 |
0.001 |
0.100 |
0.905 |
5 |
Milk protein |
0.027 |
2.077 |
0.129 |
0.002 |
0.154 |
0.857 |
Table
4: The
proportion and reliability of the influence of the prolactin genotype on the
indicators of milk production of cows.
? |
Indicator |
1st
lactation |
3rd
lactation | ||||
?2, % |
Ffactual |
? |
?2, % |
Ffactual |
? | ||
1 |
Milk yield per
lactation |
0.018 |
1.327 |
0.268 |
0.014 |
1.130 |
0.325 |
2 |
Mass fraction
of fat |
0.012 |
0.914 |
0.403 |
0.044 |
3.822* |
0.024 |
3 |
Milk fat |
0.012 |
0.889 |
0.413 |
0.001 |
0.111 |
0.895 |
4 |
Mass fraction
of protein |
0.004 |
0.280 |
0.756 |
0.022 |
1.850 |
0.161 |
5 |
Milk protein |
0.018 |
1.378 |
0.255 |
0.009 |
0.759 |
0.470 |
According to the prolactin gene; a significant
proportion of the influence is observed in cows in the 3rd lactation in terms
of the mass fraction of fat in milk ?2= 0.044 (F= 3.822; P<0.05) (table 4).
No significant and reliable influence was found in terms of other indicators (Table
3).
Thus; it was revealed
that the kappa-casein gene had the greatest influence on the mass fraction of
protein; diacylglycerol O-acyltransferase and prolactin on the mass fraction of
fat; somatotropin on milk yield. An analysis of variance was also carried out
for the influence of individual alleles of marker genes on the indicators of
milk production of cows. It was found that allele A of the kappa-casein gene
has a significant effect on the qualitative indicators of milk production of
cows: milk fat ?2= 0.035 (F= 4.727; P<0.05); the mass fraction of protein in
milk ?2= 0.036 (F= 4.879; P<0.05); milk protein ?2= 0.032 (F= 4.365;
P<0.05); provided that protein content of milk had the highest proportion of
influence. Allele B of the kappa-casein gene has a significant effect only on
the mass fraction of protein ?2= 0.342 with a high value of Fisher's criterion
that is Ffactual= 26.489 (P<0.001). This suggests that both the genotype and
the allele of kappa-casein are closely related to the high protein content of
milk of animals. Consequently; the protein content of milk of cows is 34-35%
dependent on the kappa-casein gene and its allelic variant. The degree of
influence of the desired B allele on other indicators of milk production was
less than ?2= 0.013 Allele A of the diacylglycerol O-acyltransferase gene had
the greatest effect on the amount of milk fat that was ?2= 0.058 (F= 7.949;
P<0.01). It also had a significant effect on milk yield ?2= 0.045 (F= 6.175;
P<0.05) and the milkness index ?2= 0.056 (F= 7.743; P<0.01); which was
not observed for allele A of the kappa-casein gene. The desired allele K of the
diacylglycerol O-acyltransferase gene had the greatest significant influence on
the fat mass fraction in the milk of first-calf heifers; its influence was ?2=
0.163 (F= 17.305; P<0.001). Also; the significant influence of this allele
was in terms of the mass fraction of protein in milk ?2= 0.061 (F= 5.739;
P<0.05) and according to the milkness index ?2= 0.051 (F= 4.794; P<0.05).
Consequently; it also will be possible to achieve an increase in protein
content of milk with a targeted fat content of milk. The allele V of the
somatotropin gene has a significant effect only on the yield of milk protein
?2= 0.097 with the value of Fisher's criterion that is Ffactual= 3.641
(P<0.05). For alleles A and B of the prolactin gene; no reliable and
significant influences on the indicators of milk production of cows were
revealed (Table 4).
The genotype and allele B of kappa-casein has
the strongest and most reliable effect on protein content of milk; the genotype
and allele K of diacylglycerol O-acyltransferase and also prolactin genotype on
fat content of milk; Somatotropin genotype on the level of milk yield. At the
same time; among the studied marker genes the CSN3 and DGAT1 genes have a wider
influence on the indicators of milk production.