Regression coefficient of semen characteristics of buffalo bulls on seminal plasma proteins

An experiment was carried out to explore the regression coefficients (RC) of semen characteristics on seminal proteins of buffalo bulls. SDS-PAGE resolved seminal proteins. A life sperm (LS) percentage exhibited a negative and significant RC on PF1 (111.5 ± 18.0 kDa), PF4 (36.13 ± 3.33 kDa), and PF5 (28. 88 ± 3.26 kDa) proteins, namely -0.13, -0.63 and -0.69 % / kDa respectively. A sperm acrosome integrity (SAI) percentage exhibited a pronounced negative RC on PF1 and PF2 (87.63 ± 16.5 kDa), -0.13 and -0.14 % / kDa, respectively. A negative RC was noticed in SAI percentage on PF4 (-0.61 % / kDa) and PF5 (-0.60 % / kDa) proteins. A pronounced positive RC was shown for total sperm abnormalities (TSA) on PF1 proteins (0.02 % / kDa). In conclusion, some semen attributes had a negative RC on some seminal proteins. In conclusion, some semen attributes had a negative RC on seminal proteins. These provide us with a good tool for early predicting the buffalo bull’s fertility to reduce the economic losses of male infertility and enhance the developmental sustainability of buffalo production in Iraq.


Introduction
Male fertility depends on many endocrine and genetic factors affecting the sperm output that can efficiently reach the site of fertilization [1].Prediction of bull fertility is of great importance in creating an efficient dairy industry.It will consequently increase the buffalo owner's income and improve agricultural sustainability [1].The valuation of bull fertility is the central defiance facing the AI centers and owners of buffaloes.Further, semen evaluations embraced in these centers are not dependable globally to examine the current bull's fertility.[2,3].The field bull's fertility is influenced by several factors based on the buffaloes' pregnancy rate, including the bull's genotype, full-ability of the reproductive organs, semen characteristics, and protocols for semen cryopreservation [4][5][6][7].
Biomarkers such as various proteins and other biochemical attributes play an important role in the biological systems of bulls.Still, details concerning their presence in seminal plasma, their significance in sperm metabolism, and their relation to bull fertility were not investigated extensively [8,9,10].The proteins in seminal plasma have an essential role in sperm protection, their capacitation inside the female reproductive tract, acrosome reaction, sperm-egg binding, and early conception and embryonic development [11,12].Detection of seminal proteins for good and bad semen will provide further details concerning the early prediction of buffalo bull fertility via their role in sperm metabolism.On this subject, Sharma et al. [13] found a relationship between the good-semen quality of buffalo bulls and seminal plasma proteins.Still, they needed to find their relation with the poor quality of these bulls.The regression coefficients of semen characteristics for the buffalo bulls on protein types in seminal plasma were not previously investigated in Iraqi buffalo bulls (Bubalus bubalis).For this reason, a study was conducted to determine these goals.

Animals and Design
An experiment was undertaken using eight buffalo bulls at the Artificial Insemination Department, Iraq.Bulls were under continuous veterinary superintendence.Bulls are fed a concentrate diet of barley, wheat bran, yellow corn, soybean meal, limestone, and vitamins and minerals.Concomitantly, hay and alfalfa green forage were introduced to each bull daily [9].

Detection of Seminal Plasma Proteins
An ejaculate was collected and the seminal plasma was separated (3000 rpm for 15 min.).The SDS-PAGE method (13.5%) was used to identify the seminal proteins according to their molecular weight [9,20].The standard proteins (10-250 kDa) were used to determine the molecular of identified proteins [9].

Statistical Analysis
Data were computed using a statistical analysis system [SAS, 21].Duncan's multiple range test compared significant means [22].Exponential equations were used based on the simple non-linear regression with the coefficient of determination (R 2 ) calculation to explore the regression coefficient of semen characteristics on seminal proteins.

Regression Coefficient of Semen Attributes on PF1 Protein Type
The live sperm (LS) percentage exhibited a pronounced (P≤0.01) and negative RC on seminal PF1 proteins (111.5 ± 18.0 kDa) of the buffalo bulls, namely -0.13 % / kDa with 0.7 R 2 (Table 1).On the contrary, a prominent (P≤0.05) and positive RC was observed for the total sperm abnormalities (TSA) on PF1 proteins (0.02 % / kDa) with 0.5 R 2 (Table 1).It means that the percentage of TSA increased by 0.02% when the amount of PF1 proteins increased by 1 kDa.A sperm acrosome integrity (SAI) percentage had a significant (P≤0.01) and negative RC on PF1 proteins, namely -0.13 % / kDa with 0.77 R 2 (Table 1).Similarly, a normal sperm (NS) percentage exhibited a pronounced (P≤0.05) and negative RC on PF1 proteins in seminal plasma (-0.1 % / kDa) with 0.55 R 2 (Table 1).Non-significant RC was noticed for the other semen characteristics on PF1 proteins in seminal plasma (Table 1).

Regression Coefficient of Semen Attributes on PF2 Protein Type
A prominent (P≤0.05) and negative RC was observed for the LS percentage on PF2 protein types (87.63 ± 16.5 kDa), namely -0.13 % / kDa with 0.62 R 2 (Table 2).Concomitantly, the SAI percentage exhibited a significant and negative RC on PF2 protein types (-0.14 % / kDa) with 0.74 R 2 (Table 2).The RC of the remaining semen attributes on PF2 protein types exhibited non-significance (Table 2).NS: Non-significant.

Regression
Fertility differences exist among buffalo bulls with good semen attributes, and those with comprehensible sperm deformities might not achieve good fertility [23][24][25].Seminal plasma proteins appear to participate in bull fertility because they regulate sperm viability and function as well as affect the capability of sperms to interrelate with the female genital tract and its secretion; it then acts as signal carriers for the immune system of the females [26].In the current study, an effort was made to find a prediction equation of semen attributes on different seminal protein types in Iraqi buffalo bulls as Moreover, the prediction based on RC analysis will be more reliable and near to reality [27].
Excluding data on SCIM, LS, SAI, and TSA semen characteristics, other studied attributes did not exhibit significant RC on protein types in seminal plasma (Tables 1-5).Concomitantly, Abdulkareem and Musa [9] found negative and positive significant and non-significant correlation coefficients (CC) between some semen parameters and the seminal proteins of Iraqi buffalo bulls.Similarly, Sharma et al. [13] found positive and non-significant CC between ejaculate volume and the 70 kDa protein type (r = 0.38).The CC is negative and non-significant between ejaculate volume and 38 (r = -0.35),66 (r = -0.55),and 86 (r=-0.34)kDa protein types of Indian buffalo bulls.Sharma et al. [13] found that a positive correlation coefficient existed between plasma membrane integrity and 26 and 35 kDa protein types.In contrast, the correlation of sperm acrosome integrity was positive with 24, 43, 70, and 72 kDa types.Study of Asadpour et al. [28] found a significant correlation between 55 kDa type and LS percentage.These findings suggest that some proteins may regulate sperm function by providing energy and protecting spermatogonia as supportive substances [28].

Conclusion
Some semen attributes had a negative RC on some protein types in seminal plasma.It provides us with a good tool for predicting the fertility of buffalo bulls early to reduce the economic losses of male infertility that owners incur.Accurately measuring the buffalo bull fertility is advantageous in increasing high-value sires on genetic progress and the agricultural production system in Iraq.

Table 1 .
The regression coefficient for semen characteristics of Iraqi buffalo bulls on PF1 protein types (111.5 ± 18.0 kDa) in seminal plasma.

Table 2 .
The Regression coefficient for semen attributes of Iraqi buffalo bulls on PF2 proteins (87.63 ± 16.5 kDa) in seminal plasma.

Table 3 .
The regression coefficient for semen characteristics of Iraqi buffalo bulls on PF3 protein types (43.63 ± 3.14 kDa) in seminal plasma.

Table 4 .
The regression coefficient for semen characteristics on Iraqi buffalo bulls PF4 protein types (36.13 ± 3.33 kDa) in seminal plasma.

Table 5 .
The regression coefficient for semen characteristics of Iraqi buffalo bulls on PF5 protein types (28.88 ± 3.26 kDa) in seminal plasma.
It is the first study in Iraq and the world that deals with the RC of semen attributes of Iraqi buffalo bulls on some seminal proteins.The RC analysis can give us an estimate of the degree of association between two components.It is an absolute measure of relationship.